1
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Gerard L, Duvivier L, Fourrez M, Salazar P, Sprimont L, Xia D, Ambudkar SV, Gottesman MM, Gillet JP. Identification of two novel heterodimeric ABC transporters in melanoma: ABCB5β/B6 and ABCB5β/B9. J Biol Chem 2024; 300:105594. [PMID: 38145744 PMCID: PMC10828454 DOI: 10.1016/j.jbc.2023.105594] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2023] [Revised: 11/18/2023] [Accepted: 12/15/2023] [Indexed: 12/27/2023] Open
Abstract
ABCB5 is a member of the ABC transporter superfamily composed of 48 transporters, which have been extensively studied for their role in cancer multidrug resistance and, more recently, in tumorigenesis. ABCB5 has been identified as a marker of skin progenitor cells, melanoma, and limbal stem cells. It has also been associated with multidrug resistance in several cancers. The unique feature of ABCB5 is that it exists as both a full transporter (ABCB5FL) and a half transporter (ABCB5β). Several studies have shown that the ABCB5β homodimer does not confer multidrug resistance, in contrast to ABCB5FL. In this study, using three complementary techniques, (1) nanoluciferase-based bioluminescence resonance energy transfer, (2) coimmunoprecipitation, and (3) proximity ligation assay, we identified two novel heterodimers in melanoma: ABCB5β/B6 and ABCB5β/B9. Both heterodimers could be expressed in High-Five insect cells and ATPase assays revealed that both functional nucleotide-binding domains of homodimers and heterodimers are required for their basal ATPase activity. These results are an important step toward elucidating the functional role of ABCB5β in melanocytes and melanoma.
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Affiliation(s)
- Louise Gerard
- Laboratory of Molecular Cancer Biology, URPhyM, NARILIS, University of Namur, Namur, Belgium
| | - Laurent Duvivier
- Laboratory of Molecular Cancer Biology, URPhyM, NARILIS, University of Namur, Namur, Belgium
| | - Marie Fourrez
- Laboratory of Molecular Cancer Biology, URPhyM, NARILIS, University of Namur, Namur, Belgium
| | - Paula Salazar
- Laboratory of Cell Biology, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, Maryland, USA
| | - Lindsay Sprimont
- Laboratory of Molecular Cancer Biology, URPhyM, NARILIS, University of Namur, Namur, Belgium
| | - Di Xia
- Laboratory of Cell Biology, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, Maryland, USA
| | - Suresh V Ambudkar
- Laboratory of Cell Biology, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, Maryland, USA
| | - Michael M Gottesman
- Laboratory of Cell Biology, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, Maryland, USA
| | - Jean-Pierre Gillet
- Laboratory of Molecular Cancer Biology, URPhyM, NARILIS, University of Namur, Namur, Belgium.
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2
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Fieweger RA, Wilburn KM, Montague CR, Roszkowski EK, Kelly CM, Southard TL, Sondermann H, Nazarova EV, VanderVen BC. MceG stabilizes the Mce1 and Mce4 transporters in Mycobacterium tuberculosis. J Biol Chem 2023; 299:102910. [PMID: 36642182 PMCID: PMC9947336 DOI: 10.1016/j.jbc.2023.102910] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2022] [Revised: 12/28/2022] [Accepted: 12/29/2022] [Indexed: 01/15/2023] Open
Abstract
Lipids are important nutrients for Mycobacterium tuberculosis (Mtb) to support bacterial survival in mammalian tissues and host cells. Fatty acids and cholesterol are imported across the Mtb cell wall via the dedicated Mce1 and Mce4 transporters, respectively. It is thought that the Mce1 and Mce4 transporters are comprised of subunits that confer substrate specificity and proteins that couple lipid transport to ATP hydrolysis, similar to other bacterial ABC transporters. However, unlike canonical bacterial ABC transporters, Mce1 and Mce4 appear to share a single ATPase, MceG. Previously, it was established that Mce1 and Mce4 are destabilized when key transporter subunits are rendered nonfunctional; therefore, we investigated here the role of MceG in Mce1 and Mce4 protein stability. We determined that key residues in the Walker B domain of MceG are required for the Mce1- and Mce4-mediated transport of fatty acids and cholesterol. Previously, it has been established that Mce1 and Mce4 are destabilized and/or degraded when key transporter subunits are rendered nonfunctional, thus we investigated a role for MceG in stabilizing Mce1 and Mce4. Using an unbiased quantitative proteomic approach, we demonstrate that Mce1 and Mce4 proteins are specifically degraded in mutants lacking MceG. Furthermore, bacteria expressing Walker B mutant variants of MceG failed to stabilize Mce1 and Mce4, and we show that deleting MceG impacts the fitness of Mtb in the lungs of mice. Thus, we conclude that MceG represents an enzymatic weakness that can be potentially leveraged to disable and destabilize both the Mce1 and Mce4 transporters in Mtb.
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Affiliation(s)
- Rachael A Fieweger
- Microbiology & Immunology, College of Veterinary Medicine, Cornell University, Ithaca New York, USA
| | - Kaley M Wilburn
- Microbiology & Immunology, College of Veterinary Medicine, Cornell University, Ithaca New York, USA
| | - Christine R Montague
- Microbiology & Immunology, College of Veterinary Medicine, Cornell University, Ithaca New York, USA
| | - Emma K Roszkowski
- Microbiology & Immunology, College of Veterinary Medicine, Cornell University, Ithaca New York, USA
| | - Carolyn M Kelly
- Molecular Medicine, College of Veterinary Medicine, Cornell University, Ithaca New York, USA
| | - Teresa L Southard
- Biomedical Sciences; College of Veterinary Medicine, Cornell University, Ithaca New York, USA
| | - Holger Sondermann
- Molecular Medicine, College of Veterinary Medicine, Cornell University, Ithaca New York, USA
| | - Evgeniya V Nazarova
- Microbiology & Immunology, College of Veterinary Medicine, Cornell University, Ithaca New York, USA
| | - Brian C VanderVen
- Microbiology & Immunology, College of Veterinary Medicine, Cornell University, Ithaca New York, USA.
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3
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Harris A, Wagner M, Du D, Raschka S, Nentwig LM, Gohlke H, Smits SHJ, Luisi BF, Schmitt L. Structure and efflux mechanism of the yeast pleiotropic drug resistance transporter Pdr5. Nat Commun 2021; 12:5254. [PMID: 34489436 PMCID: PMC8421411 DOI: 10.1038/s41467-021-25574-8] [Citation(s) in RCA: 34] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2021] [Accepted: 08/11/2021] [Indexed: 11/24/2022] Open
Abstract
Pdr5, a member of the extensive ABC transporter superfamily, is representative of a clinically relevant subgroup involved in pleiotropic drug resistance. Pdr5 and its homologues drive drug efflux through uncoupled hydrolysis of nucleotides, enabling organisms such as baker’s yeast and pathogenic fungi to survive in the presence of chemically diverse antifungal agents. Here, we present the molecular structure of Pdr5 solved with single particle cryo-EM, revealing details of an ATP-driven conformational cycle, which mechanically drives drug translocation through an amphipathic channel, and a clamping switch within a conserved linker loop that acts as a nucleotide sensor. One half of the transporter remains nearly invariant throughout the cycle, while its partner undergoes changes that are transmitted across inter-domain interfaces to support a peristaltic motion of the pumped molecule. The efflux model proposed here rationalises the pleiotropic impact of Pdr5 and opens new avenues for the development of effective antifungal compounds. Pdr5 is an ABC transporter conferring multidrug resistance to pathogenic fungi. Here, structural analysis of Pdr5 provides insights into the transport mechanism featuring asymmetric movements of Pdr5 domain and enabling efflux of a broad spectrum of compounds.
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Affiliation(s)
- Andrzej Harris
- Department of Biochemistry, University of Cambridge, Cambridge, UK
| | - Manuel Wagner
- Institute of Biochemistry, Heinrich Heine University Düsseldorf, Universitätsstraße 1, Düsseldorf, Germany.,Medac GmbH, Theatherstraße 6, Wedel, Germany
| | - Dijun Du
- Department of Biochemistry, University of Cambridge, Cambridge, UK.,School of Life Sciences and Technology, ShanghaiTech University, Pudong, Shanghai, China
| | - Stefanie Raschka
- Institute of Biochemistry, Heinrich Heine University Düsseldorf, Universitätsstraße 1, Düsseldorf, Germany
| | - Lea-Marie Nentwig
- Institute of Biochemistry, Heinrich Heine University Düsseldorf, Universitätsstraße 1, Düsseldorf, Germany
| | - Holger Gohlke
- Institute of Pharmaceutical and Medicinal Pharmacy, Heinrich Heine University Düsseldorf, Universitätsstraße 1, Düsseldorf, Germany.,John von Neumann Institute for Computing (NIC), Jülich Supercomputing Centre (JSC), Forschungszentrum Jülich GmbH, Jülich, Germany.,Institute of Biological Information Processing (IBI-7: Structural Biochemistry), Forschungszentrum Jülich GmbH, Jülich, Germany.,Institute of Bio- and Geosciences (IBG-4: Bioinformatics), Forschungszentrum Jülich GmbH, Jülich, Germany
| | - Sander H J Smits
- Institute of Biochemistry, Heinrich Heine University Düsseldorf, Universitätsstraße 1, Düsseldorf, Germany.,Center for Structural Studies, Heinrich Heine University Düsseldorf, Universitätsstraße 1, Düsseldorf, Germany
| | - Ben F Luisi
- Department of Biochemistry, University of Cambridge, Cambridge, UK.
| | - Lutz Schmitt
- Institute of Biochemistry, Heinrich Heine University Düsseldorf, Universitätsstraße 1, Düsseldorf, Germany.
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4
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Szeri F, Niaziorimi F, Donnelly S, Orndorff J, van de Wetering K. Generation of fully functional fluorescent fusion proteins to gain insights into ABCC6 biology. FEBS Lett 2021; 595:799-810. [PMID: 33058196 PMCID: PMC7987643 DOI: 10.1002/1873-3468.13957] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2020] [Revised: 09/04/2020] [Accepted: 09/29/2020] [Indexed: 12/18/2022]
Abstract
ABCC6 mediates release of ATP from hepatocytes into the blood. Extracellularly, ATP is converted into the mineralization inhibitor pyrophosphate. Consequently, inactivating mutations in ABCC6 give low plasma pyrophosphate and underlie the ectopic mineralization disorder pseudoxanthoma elasticum. How ABCC6 mediates cellular ATP release is still unknown. Fluorescent ABCC6 fusion proteins would allow mechanistic studies, but fluorophores attached to the ABCC6 N- or C-terminus result in intracellular retention and degradation. Here we describe that intramolecular introduction of fluorophores yields fully functional ABCC6 fusion proteins. A corresponding ABCC6 variant in which the catalytic glutamate of the second nucleotide binding domain was mutated, correctly routed to the plasma membrane but was inactive. Finally, N-terminal His10 or FLAG tags did not affect activity of the fusion proteins, allowing their purification for biochemical characterization.
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Affiliation(s)
- Flora Szeri
- Department of Dermatology and Cutaneous Biology, Sidney Kimmel Medical College, Thomas Jefferson University, 19107, Philadelphia (PA), USA
- Institute of Enzymology, Research Centre for Natural Sciences, Budapest, Hungary (current address)
| | - Fatemeh Niaziorimi
- Department of Dermatology and Cutaneous Biology, Sidney Kimmel Medical College, Thomas Jefferson University, 19107, Philadelphia (PA), USA
| | - Sylvia Donnelly
- Department of Dermatology and Cutaneous Biology, Sidney Kimmel Medical College, Thomas Jefferson University, 19107, Philadelphia (PA), USA
| | - Joseph Orndorff
- Department of Dermatology and Cutaneous Biology, Sidney Kimmel Medical College, Thomas Jefferson University, 19107, Philadelphia (PA), USA
| | - Koen van de Wetering
- Department of Dermatology and Cutaneous Biology, Sidney Kimmel Medical College, Thomas Jefferson University, 19107, Philadelphia (PA), USA
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5
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Stockner T, Gradisch R, Schmitt L. The role of the degenerate nucleotide binding site in type I ABC exporters. FEBS Lett 2020; 594:3815-3838. [PMID: 33179257 PMCID: PMC7756269 DOI: 10.1002/1873-3468.13997] [Citation(s) in RCA: 26] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2020] [Revised: 09/26/2020] [Accepted: 10/15/2020] [Indexed: 12/18/2022]
Abstract
ATP‐binding cassette (ABC) transporters are fascinating molecular machines that are capable of transporting a large variety of chemically diverse compounds. The energy required for translocation is derived from binding and hydrolysis of ATP. All ABC transporters share a basic architecture and are composed of two transmembrane domains and two nucleotide binding domains (NBDs). The latter harbor all conserved sequence motifs that hallmark the ABC transporter superfamily. The NBDs form the nucleotide binding sites (NBSs) in their interface. Transporters with two active NBSs are called canonical transporters, while ABC exporters from eukaryotic organisms, including humans, frequently have a degenerate NBS1 containing noncanonical residues that strongly impair ATP hydrolysis. Here, we summarize current knowledge on degenerate ABC transporters. By integrating structural information with biophysical and biochemical evidence of asymmetric function, we develop a model for the transport cycle of degenerate ABC transporters. We will elaborate on the unclear functional advantages of a degenerate NBS.
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Affiliation(s)
- Thomas Stockner
- Institute of Pharmacology, Center for Physiology and Pharmacology, Medical University of Vienna, Vienna, Austria
| | - Ralph Gradisch
- Institute of Pharmacology, Center for Physiology and Pharmacology, Medical University of Vienna, Vienna, Austria
| | - Lutz Schmitt
- Institute of Biochemistry, Heinrich Heine University, Düsseldorf, Germany
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6
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Csanády L, Vergani P, Gadsby DC. STRUCTURE, GATING, AND REGULATION OF THE CFTR ANION CHANNEL. Physiol Rev 2019; 99:707-738. [PMID: 30516439 DOI: 10.1152/physrev.00007.2018] [Citation(s) in RCA: 140] [Impact Index Per Article: 28.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
The cystic fibrosis transmembrane conductance regulator (CFTR) belongs to the ATP binding cassette (ABC) transporter superfamily but functions as an anion channel crucial for salt and water transport across epithelial cells. CFTR dysfunction, because of mutations, causes cystic fibrosis (CF). The anion-selective pore of the CFTR protein is formed by its two transmembrane domains (TMDs) and regulated by its cytosolic domains: two nucleotide binding domains (NBDs) and a regulatory (R) domain. Channel activation requires phosphorylation of the R domain by cAMP-dependent protein kinase (PKA), and pore opening and closing (gating) of phosphorylated channels is driven by ATP binding and hydrolysis at the NBDs. This review summarizes available information on structure and mechanism of the CFTR protein, with a particular focus on atomic-level insight gained from recent cryo-electron microscopic structures and on the molecular mechanisms of channel gating and its regulation. The pharmacological mechanisms of small molecules targeting CFTR's ion channel function, aimed at treating patients suffering from CF and other diseases, are briefly discussed.
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Affiliation(s)
- László Csanády
- Department of Medical Biochemistry, Semmelweis University , Budapest , Hungary ; MTA-SE Ion Channel Research Group, Budapest , Hungary ; Department of Neuroscience, Physiology and Pharmacology, University College London , London , United Kingdom ; and Laboratory of Cardiac/Membrane Physiology, The Rockefeller University , New York, New York
| | - Paola Vergani
- Department of Medical Biochemistry, Semmelweis University , Budapest , Hungary ; MTA-SE Ion Channel Research Group, Budapest , Hungary ; Department of Neuroscience, Physiology and Pharmacology, University College London , London , United Kingdom ; and Laboratory of Cardiac/Membrane Physiology, The Rockefeller University , New York, New York
| | - David C Gadsby
- Department of Medical Biochemistry, Semmelweis University , Budapest , Hungary ; MTA-SE Ion Channel Research Group, Budapest , Hungary ; Department of Neuroscience, Physiology and Pharmacology, University College London , London , United Kingdom ; and Laboratory of Cardiac/Membrane Physiology, The Rockefeller University , New York, New York
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7
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Nürenberg-Goloub E, Heinemann H, Gerovac M, Tampé R. Ribosome recycling is coordinated by processive events in two asymmetric ATP sites of ABCE1. Life Sci Alliance 2018; 1. [PMID: 30198020 PMCID: PMC6124641 DOI: 10.26508/lsa.201800095] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
The stepwise ribosome disassembly in the translation cycle of eukaryotes and archaea is scheduled by discrete molecular events within the asymmetric ribosome recycling factor ABCE1. Ribosome recycling orchestrated by ABCE1 is a fundamental process in protein translation and mRNA surveillance, connecting termination with initiation. Beyond the plenitude of well-studied translational GTPases, ABCE1 is the only essential factor energized by ATP, delivering the energy for ribosome splitting via two nucleotide-binding sites by a yet unknown mechanism. Here, we define how allosterically coupled ATP binding and hydrolysis events in ABCE1 empower ribosome recycling. ATP occlusion in the low-turnover control site II promotes formation of the pre-splitting complex and facilitates ATP engagement in the high-turnover site I, which in turn drives the structural reorganization required for ribosome splitting. ATP hydrolysis and ensuing release of ABCE1 from the small subunit terminate the post-splitting complex. Thus, ABCE1 runs through an allosterically coupled cycle of closure and opening at both sites, consistent with a processive clamp model. This study delineates the inner mechanics of ABCE1 and reveals why various ABCE1 mutants lead to defects in cell homeostasis, growth, and differentiation.
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Affiliation(s)
- Elina Nürenberg-Goloub
- Institute of Biochemistry, Biocenter, Goethe University Frankfurt, Max-von-Laue-Str. 9, 60438 Frankfurt a.M., Germany
| | - Holger Heinemann
- Institute of Biochemistry, Biocenter, Goethe University Frankfurt, Max-von-Laue-Str. 9, 60438 Frankfurt a.M., Germany
| | - Milan Gerovac
- Institute of Biochemistry, Biocenter, Goethe University Frankfurt, Max-von-Laue-Str. 9, 60438 Frankfurt a.M., Germany
| | - Robert Tampé
- Institute of Biochemistry, Biocenter, Goethe University Frankfurt, Max-von-Laue-Str. 9, 60438 Frankfurt a.M., Germany
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8
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Loo TW, Clarke DM. A short cross-linker activates human P-glycoprotein missing a catalytic carboxylate. Biochem Pharmacol 2017; 145:27-33. [PMID: 28837794 DOI: 10.1016/j.bcp.2017.08.014] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2017] [Accepted: 08/18/2017] [Indexed: 11/17/2022]
Abstract
P-glycoprotein (P-gp) is an ATP-dependent drug pump that protects us from toxic agents and confers multidrug resistance. It has a tweezer-like structure with each arm consisting of a transmembrane domain (TMD) and a nucleotide-binding domain (NBD). Drug substrates bind to sites within the TMDs to activate ATPase activity by promoting a tweezer-like closing of the gap between the NBDs. The catalytic carboxylates may be critical for NBD movements because the E556Q(NBD1) or E1201Q(NBD2) mutation inhibited drug-stimulated ATPase activity. If the catalytic carboxylates were components of the mechanism to bring the NBDs together, then we predicted that insertion of a flexible cross-linker between the arms would increase ATPase activity of the mutants. We found that cross-linking (between L175C(TMD1) and N820C(TMD2)) with a short flexible cross-linker (7.8Å maximum) restored high levels of drug-stimulated ATPase activity of the E556Q or E1201Q mutants. Cross-linking with a longer cross-linker (22Å maximum) however, did not restore activity. Cross-linking could not rescue all ATPase deficient mutants. For example, cross-linking L175C/N820C with short or long cross-linkers did not activate the H-loop mutants H587A or H1232A or the Walker A K433M or K1076M mutants. The results suggest that the E556 and E1201 catalytic carboxylates are part of a spring-like mechanism that is required to facilitate movements between the open and closed conformations of P-gp during ATP hydrolysis.
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Affiliation(s)
- Tip W Loo
- Department of Medicine and Department of Biochemistry, University of Toronto, Toronto, Ontario M5S 1A8, Canada
| | - David M Clarke
- Department of Medicine and Department of Biochemistry, University of Toronto, Toronto, Ontario M5S 1A8, Canada.
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9
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Dong Q, Ernst SE, Ostedgaard LS, Shah VS, Ver Heul AR, Welsh MJ, Randak CO. Mutating the Conserved Q-loop Glutamine 1291 Selectively Disrupts Adenylate Kinase-dependent Channel Gating of the ATP-binding Cassette (ABC) Adenylate Kinase Cystic Fibrosis Transmembrane Conductance Regulator (CFTR) and Reduces Channel Function in Primary Human Airway Epithelia. J Biol Chem 2015; 290:14140-53. [PMID: 25887396 PMCID: PMC4447984 DOI: 10.1074/jbc.m114.611616] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2014] [Indexed: 11/06/2022] Open
Abstract
The ATP-binding cassette (ABC) transporter cystic fibrosis transmembrane conductance regulator (CFTR) and two other non-membrane-bound ABC proteins, Rad50 and a structural maintenance of chromosome (SMC) protein, exhibit adenylate kinase activity in the presence of physiologic concentrations of ATP and AMP or ADP (ATP + AMP ⇆ 2 ADP). The crystal structure of the nucleotide-binding domain of an SMC protein in complex with the adenylate kinase bisubstrate inhibitor P(1),P(5)-di(adenosine-5') pentaphosphate (Ap5A) suggests that AMP binds to the conserved Q-loop glutamine during the adenylate kinase reaction. Therefore, we hypothesized that mutating the corresponding residue in CFTR, Gln-1291, selectively disrupts adenylate kinase-dependent channel gating at physiologic nucleotide concentrations. We found that substituting Gln-1291 with bulky side-chain amino acids abolished the effects of Ap5A, AMP, and adenosine 5'-monophosphoramidate on CFTR channel function. 8-Azidoadenosine 5'-monophosphate photolabeling of the AMP-binding site and adenylate kinase activity were disrupted in Q1291F CFTR. The Gln-1291 mutations did not alter the potency of ATP at stimulating current or ATP-dependent gating when ATP was the only nucleotide present. However, when physiologic concentrations of ADP and AMP were added, adenylate kinase-deficient Q1291F channels opened significantly less than wild type. Consistent with this result, we found that Q1291F CFTR displayed significantly reduced Cl(-) channel function in well differentiated primary human airway epithelia. These results indicate that a highly conserved residue of an ABC transporter plays an important role in adenylate kinase-dependent CFTR gating. Furthermore, the results suggest that adenylate kinase activity is important for normal CFTR channel function in airway epithelia.
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Affiliation(s)
- Qian Dong
- From the Stead Family Department of Pediatrics
| | - Sarah E Ernst
- the Department of Internal Medicine, the Howard Hughes Medical Institute, Iowa City, Iowa 52242
| | | | - Viral S Shah
- the Department of Molecular Physiology and Biophysics, and the Medical Scientist Training Program, University of Iowa, Iowa City, Iowa 52242 and
| | | | - Michael J Welsh
- the Department of Internal Medicine, the Howard Hughes Medical Institute, Iowa City, Iowa 52242 the Department of Molecular Physiology and Biophysics, and
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10
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Ortiz D, Bryan J. Neonatal Diabetes and Congenital Hyperinsulinism Caused by Mutations in ABCC8/SUR1 are Associated with Altered and Opposite Affinities for ATP and ADP. Front Endocrinol (Lausanne) 2015; 6:48. [PMID: 25926814 PMCID: PMC4397924 DOI: 10.3389/fendo.2015.00048] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/27/2014] [Accepted: 03/21/2015] [Indexed: 12/28/2022] Open
Abstract
ATP-sensitive K(+) (KATP) channels composed of potassium inward-rectifier type 6.2 and sulfonylurea receptor type 1 subunits (Kir6.2/SUR1)4 are expressed in various cells in the brain and endocrine pancreas where they couple metabolic status to membrane potential. In β-cells, increases in cytosolic [ATP/ADP]c inhibit KATP channel activity, leading to membrane depolarization and exocytosis of insulin granules. Mutations in ABCC8 (SUR1) or KCNJ11 (Kir6.2) can result in gain or loss of channel activity and cause neonatal diabetes (ND) or congenital hyperinsulinism (CHI), respectively. SUR1 is reported to be a Mg(2+)-dependent ATPase. A prevailing model posits that ATP hydrolysis at SUR1 is required to stimulate openings of the pore. However, recent work shows nucleotide binding, without hydrolysis, is sufficient to switch SUR1 to stimulatory conformations. The actions of nucleotides, ATP and ADP, on ND (SUR1E1506D) and CHI (SUR1E1506K) mutants, without Kir6.2, were compared to assess both models. Both substitutions significantly impair hydrolysis in SUR1 homologs. SUR1E1506D has greater affinity for MgATP than wildtype; SUR1E1506K has reduced affinity. Without Mg(2+), SUR1E1506K has a greater affinity for ATP(4-) consistent with electrostatic attraction between ATP(4-), unshielded by Mg(2+), and the basic lysine. Further analysis of ND and CHI ABCC8 mutants in the second transmembrane and nucleotide-binding domains (TMD2 and NBD2) found a relation between their affinities for ATP (±Mg(2+)) and their clinical phenotype. Increased affinity for ATP is associated with ND; decreased affinity with CHI. In contrast, MgADP showed a weaker relationship. Diazoxide, known to reduce insulin release in some CHI cases, potentiates switching of CHI mutants from non-stimulatory to stimulatory states consistent with diazoxide stabilizing a nucleotide-bound conformation. The results emphasize the greater importance of nucleotide binding vs. hydrolysis in the regulation of KATP channels in vivo.
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Affiliation(s)
- David Ortiz
- Department of Medicinal Chemistry, University of Washington, Seattle, WA, USA
| | - Joseph Bryan
- Pacific Northwest Diabetes Research Institute, Seattle, WA, USA
- *Correspondence: Joseph Bryan, Pacific Northwest Diabetes Research Institute, 720 Broadway, Seattle, WA 98122, USA e-mail:
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11
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Zolnerciks JK, Akkaya BG, Snippe M, Chiba P, Seelig A, Linton KJ. The Q loops of the human multidrug resistance transporter ABCB1 are necessary to couple drug binding to the ATP catalytic cycle. FASEB J 2014; 28:4335-46. [PMID: 25016028 DOI: 10.1096/fj.13-245639] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
For a primary active pump, such as the human ATP-binding-cassette (ABC) transporter ABCB1, coupling of drug-binding by the two transmembrane domains (TMDs) to the ATP catalytic cycle of the two nucleotide-binding domains (NBDs) is fundamental to the transport mechanism, but is poorly understood at the biochemical level. Structure data suggest that signals are transduced through intracellular loops of the TMDs that slot into grooves on the NBDs. At the base of these grooves is the Q loop. We therefore mutated the eponymous glutamine in one or both NBD Q loops and measured the effect on conformation and function by using a conformation-sensitive antibody (UIC2) and a fluorescent drug (Bodipy-verapamil), respectively. We showed that the double mutant is trapped in the inward-open state, which binds the drug, but cannot couple to the ATPase cycle. Our data also describe marked redundancy within the transport mechanism, because single-Q-loop mutants are functional for Bodipy-verapamil transport. This result allowed us to elucidate transduction pathways from twin drug-binding cavities to the Q loops using point mutations to favor one cavity over the other. Together, the data show that the Q loop is the central flexion point where the aspect of the drug-binding cavities is coupled to the ATP catalytic cycle.
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Affiliation(s)
- Joseph K Zolnerciks
- Blizard Institute, Barts and The London School of Medicine and Dentistry, Queen Mary, University of London, London UK
| | - Begum G Akkaya
- Blizard Institute, Barts and The London School of Medicine and Dentistry, Queen Mary, University of London, London UK
| | - Marjolein Snippe
- Blizard Institute, Barts and The London School of Medicine and Dentistry, Queen Mary, University of London, London UK
| | - Peter Chiba
- Institute of Medical Chemistry, Medical University of Vienna, Vienna, Austria; and
| | - Anna Seelig
- Biophysical Chemistry Biozentrum, University of Basel, Basel, Switzerland
| | - Kenneth J Linton
- Blizard Institute, Barts and The London School of Medicine and Dentistry, Queen Mary, University of London, London UK;
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12
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Swartz D, Mok L, Botta S, Singh A, Altenberg G, Urbatsch I. Directed evolution of P-glycoprotein cysteines reveals site-specific, non-conservative substitutions that preserve multidrug resistance. Biosci Rep 2014; 34:e00116. [PMID: 24825346 PMCID: PMC4069687 DOI: 10.1042/bsr20140062] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2014] [Revised: 05/05/2014] [Accepted: 05/06/2014] [Indexed: 11/21/2022] Open
Abstract
Pgp (P-glycoprotein) is a prototype ABC (ATP-binding-cassette) transporter involved in multidrug resistance of cancer. We used directed evolution to replace six cytoplasmic Cys (cysteine) residues in Pgp with all 20 standard amino acids and selected for active mutants. From a pool of 75000 transformants for each block of three Cys, we identified multiple mutants that preserved drug resistance and yeast mating activity. The most frequent substitutions were glycine and serine for Cys427 (24 and 20%, respectively) and Cys1070 (37 and 25%) of the Walker A motifs in the NBDs (nucleotide-binding domains), Cys1223 in NBD2 (25 and 8%) and Cys638 in the linker region (24 and 16%), whereas close-by Cys669 tolerated glycine (16%) and alanine (14%), but not serine (absent). Cys1121 in NBD2 showed a clear preference for positively charged arginine (38%) suggesting a salt bridge with Glu269 in the ICL2 (intracellular loop 2) may stabilize domain interactions. In contrast, three Cys residues in transmembrane α-helices could be successfully replaced by alanine. The resulting CL (Cys-less) Pgp was fully active in yeast cells, and purified proteins displayed drug-stimulated ATPase activities indistinguishable from WT (wild-type) Pgp. Overall, directed evolution identified site-specific, non-conservative Cys substitutions that allowed building of a robust CL Pgp, an invaluable new tool for future functional and structural studies, and that may guide the construction of other CL proteins where alanine and serine have proven unsuccessful.
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Key Words
- abc transporter
- multidrug transporter
- non-conservative cysteine substitutions
- protein evolution site-saturation mutagenesis
- yeast drug resistance
- abc, atp-binding-cassette
- cftr, cystic fibrosis transmembrane conductance regulator
- cl, cys-less
- cp-mts, 7-diethylamino-3-(4′-maleimidylphenyl)-4-methylcoumarin
- ddm, n-dodecyl-β-d-maltopyranoside
- icl, intracellular loop
- nbd, nucleotide-binding domain
- pgp, p-glycoprotein
- sec, size exclusion chromatography
- tmd, transmembrane domain
- wt, wild-type
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Affiliation(s)
- Douglas J. Swartz
- *Department of Cell Biology and Biochemistry, Texas Tech University Health Sciences Center, Lubbock, Texas, U.S.A
- †Center for Membrane Protein Research, Texas Tech University Health Sciences Center, Lubbock, Texas, U.S.A
| | - Leo Mok
- *Department of Cell Biology and Biochemistry, Texas Tech University Health Sciences Center, Lubbock, Texas, U.S.A
- †Center for Membrane Protein Research, Texas Tech University Health Sciences Center, Lubbock, Texas, U.S.A
| | - Sri K. Botta
- *Department of Cell Biology and Biochemistry, Texas Tech University Health Sciences Center, Lubbock, Texas, U.S.A
- †Center for Membrane Protein Research, Texas Tech University Health Sciences Center, Lubbock, Texas, U.S.A
| | - Anukriti Singh
- *Department of Cell Biology and Biochemistry, Texas Tech University Health Sciences Center, Lubbock, Texas, U.S.A
- †Center for Membrane Protein Research, Texas Tech University Health Sciences Center, Lubbock, Texas, U.S.A
| | - Guillermo A. Altenberg
- †Center for Membrane Protein Research, Texas Tech University Health Sciences Center, Lubbock, Texas, U.S.A
- ‡Department of Cell Physiology and Molecular Biophysics, Texas Tech University Health Sciences Center, Lubbock, Texas, U.S.A
| | - Ina L. Urbatsch
- *Department of Cell Biology and Biochemistry, Texas Tech University Health Sciences Center, Lubbock, Texas, U.S.A
- †Center for Membrane Protein Research, Texas Tech University Health Sciences Center, Lubbock, Texas, U.S.A
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Multidrug Resistance in Cancer: A Tale of ABC Drug Transporters. RESISTANCE TO TARGETED ANTI-CANCER THERAPEUTICS 2013. [DOI: 10.1007/978-1-4614-7070-0_1] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
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14
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Liesa M, Qiu W, Shirihai OS. Mitochondrial ABC transporters function: the role of ABCB10 (ABC-me) as a novel player in cellular handling of reactive oxygen species. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2012; 1823:1945-57. [PMID: 22884976 DOI: 10.1016/j.bbamcr.2012.07.013] [Citation(s) in RCA: 60] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/11/2012] [Revised: 07/24/2012] [Accepted: 07/27/2012] [Indexed: 12/22/2022]
Abstract
Mitochondria are one of the major sources of reactive oxygen species (ROS) in the cell. When exceeding the capacity of antioxidant mechanisms, ROS production may lead to different pathologies, such as ischemia-reperfusion injury, neurodegeneration, anemia and ageing. As a consequence of the endosymbiotic origin of mitochondria, eukaryotic cells have developed different transport mechanisms that coordinate mitochondrial function with other cellular compartments. Four mitochondrial ATP-binding cassette (ABC) transporters have been described to date in mammals: ABCB6, ABCB8, ABCB7 and ABCB10. ABCB10 is located in the inner mitochondrial membrane forming homodimers, with the ATP binding domain facing the mitochondrial matrix. ABCB10 expression is highly induced during erythroid differentiation and its overexpression increases hemoglobin synthesis in erythroid cells. However, ABCB10 is also expressed in nonerythroid tissues, suggesting a role not directly related to hemoglobin synthesis. Recent evidence points toward ABCB10 as an important player in the protection from oxidative stress in mammals. In this regard, ABCB10 is required for normal erythropoiesis and cardiac recovery after ischemia-reperfusion, processes intimately related to mitochondrial ROS generation. Here, we review the current knowledge on mitochondrial ABC transporters and ABCB10 and discuss the potential mechanisms by which ABCB10 and its transport activity may regulate oxidative stress. We discuss ABCB10 as a potential therapeutic target for diseases in which increased mitochondrial ROS production and oxidative stress play a major role.
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Affiliation(s)
- Marc Liesa
- Department of Medicine, Obesity and Nutrition Section, Mitochondria ARC, Evans Biomedical Research Center, Boston University School of Medicine, Boston, MA 02118, USA
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15
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16
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Abstract
ATP-binding cassette transporters are powered by ATP, but the mechanism by which these transporters hydrolyze ATP is unclear. In this study, four crystal structures of the full-length wild-type maltose transporter, stabilized by adenosine 5'-(β,γ-imido)triphosphate or ADP in conjunction with phosphate analogs BeF(3)(-), VO(4)(3-), or AIF(4)(-), were determined to 2.2- to 2.4-Å resolution. These structures led to the assignment of two enzymatic states during ATP hydrolysis and demonstrate specific functional roles of highly conserved residues in the nucleotide-binding domain, suggesting that ATP-binding cassette transporters catalyze ATP hydrolysis via a general base mechanism.
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17
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A gene optimization strategy that enhances production of fully functional P-glycoprotein in Pichia pastoris. PLoS One 2011; 6:e22577. [PMID: 21826197 PMCID: PMC3149604 DOI: 10.1371/journal.pone.0022577] [Citation(s) in RCA: 79] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2011] [Accepted: 06/24/2011] [Indexed: 12/27/2022] Open
Abstract
BACKGROUND Structural and biochemical studies of mammalian membrane proteins remain hampered by inefficient production of pure protein. We explored codon optimization based on highly expressed Pichia pastoris genes to enhance co-translational folding and production of P-glycoprotein (Pgp), an ATP-dependent drug efflux pump involved in multidrug resistance of cancers. METHODOLOGY/PRINCIPAL FINDINGS Codon-optimized "Opti-Pgp" and wild-type Pgp, identical in primary protein sequence, were rigorously analyzed for differences in function or solution structure. Yeast expression levels and yield of purified protein from P. pastoris (∼130 mg per kg cells) were about three-fold higher for Opti-Pgp than for wild-type protein. Opti-Pgp conveyed full in vivo drug resistance against multiple anticancer and fungicidal drugs. ATP hydrolysis by purified Opti-Pgp was strongly stimulated ∼15-fold by verapamil and inhibited by cyclosporine A with binding constants of 4.2±2.2 µM and 1.1±0.26 µM, indistinguishable from wild-type Pgp. Maximum turnover number was 2.1±0.28 µmol/min/mg and was enhanced by 1.2-fold over wild-type Pgp, likely due to higher purity of Opti-Pgp preparations. Analysis of purified wild-type and Opti-Pgp by CD, DSC and limited proteolysis suggested similar secondary and ternary structure. Addition of lipid increased the thermal stability from T(m) ∼40 °C to 49 °C, and the total unfolding enthalpy. The increase in folded state may account for the increase in drug-stimulated ATPase activity seen in presence of lipids. CONCLUSION The significantly higher yields of protein in the native folded state, higher purity and improved function establish the value of our gene optimization approach, and provide a basis to improve production of other membrane proteins.
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18
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Chang XB. Molecular mechanism of ATP-dependent solute transport by multidrug resistance-associated protein 1. Methods Mol Biol 2010; 596:223-49. [PMID: 19949927 DOI: 10.1007/978-1-60761-416-6_11] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
Millions of new cancer patients are diagnosed each year and over half of these patients die from this devastating disease. Thus, cancer causes a major public health problem worldwide. Chemotherapy remains the principal mode to treat many metastatic cancers. However, occurrence of cellular multidrug resistance (MDR) prevents efficient killing of cancer cells, leading to chemotherapeutic treatment failure. Over-expression of ATP-binding cassette transporters, such as P-glycoprotein, breast cancer resistance protein and/or multidrug resistance-associated protein 1 (MRP1), confers an acquired MDR due to their capabilities of transporting a broad range of chemically diverse anticancer drugs across the cell membrane barrier. In this review, the molecular mechanism of ATP-dependent solute transport by MRP1 will be addressed.
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Affiliation(s)
- Xiu-bao Chang
- Mayo Clinic College of Medicine, Mayo Clinic Arizona, Scottsdale, AZ, USA.
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19
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Ernst R, Kueppers P, Stindt J, Kuchler K, Schmitt L. Multidrug efflux pumps: substrate selection in ATP-binding cassette multidrug efflux pumps--first come, first served? FEBS J 2009; 277:540-9. [PMID: 19961541 DOI: 10.1111/j.1742-4658.2009.07485.x] [Citation(s) in RCA: 86] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Multidrug resistance is a major challenge in the therapy of cancer and pathogenic fungal infections. More than three decades ago, P-glycoprotein was the first identified multidrug transporter. It has been studied extensively at the genetic and biochemical levels ever since. Pdr5, the most abundant ATP-binding cassette transporter in Saccharomyces cerevisiae, is highly homologous to azole-resistance-mediating multidrug transporters in fungal pathogens, and a focus of clinical drug resistance research. Despite functional equivalences, P-glycoprotein and Pdr5 exhibit striking differences in their architecture and mechanisms. In this minireview, we discuss the mechanisms of substrate selection and multidrug transport by comparing the fraternal twins P-glycoprotein and Pdr5. We propose that substrate selection in eukaryotic multidrug ATP-binding cassette transporters is not solely determined by structural features of the transmembrane domains but also by their dynamic behavior.
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Affiliation(s)
- Robert Ernst
- Institute of Biochemistry, Heinrich-Heine-University Duesseldorf, Duesseldorf, Germany
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20
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Hou YX, Li CZ, Palaniyandi K, Magtibay PM, Homolya L, Sarkadi B, Chang XB. Effects of putative catalytic base mutation E211Q on ABCG2-mediated methotrexate transport. Biochemistry 2009; 48:9122-31. [PMID: 19691360 DOI: 10.1021/bi900675v] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
ABCG2 is a half-ATP binding cassette (ABC) drug transporter that consists of a nucleotide binding domain (NBD) followed by a transmembrane domain. This half-ABC transporter is thought to form a homodimer in the plasma membrane where it transports anticancer drugs across the biological membranes in an ATP-dependent manner. Substitution of the putative catalytic residue E211 with a nonacidic amino acid glutamine (E211Q) completely abolished its ATPase activity and ATP-dependent methotrexate transport, suggesting that ATP hydrolysis is required for the ATP-dependent solute transport. However, whether one ATP hydrolysis or two ATP hydrolyses in the homodimer of ABCG2 with the NBD.ATP.ATP.NBD sandwich structure is/are required for the ATP-dependent solute transport is not known yet. To address this question, we have made an YFP/ABCG2 fusion protein and expressed this 99 kDa fusion protein alone or along with the 70 kDa E211Q-mutated ABCG2 in BHK cells. Although membrane vesicles prepared from BHK cells expressing YFP/ABCG2 exert higher ATPase activity than that of wt ABCG2, the dATP-dependent methotrexate transport activities of these two proteins are the same. Interestingly, membrane vesicles prepared from BHK cells expressing both YFP/ABCG2 and E211Q-mutated ABCG2 (with a ratio of 1:1) form homodimers and heterodimer and exert 55% of wt ABCG2 ATPase activity that can be further enhanced by anticancer drugs, suggesting that the wt NBD in the heterodimer of YFP/ABCG2 and E211Q may be able to hydrolyze ATP. Furthermore, the membrane vesicles containing both YFP/ABCG2 and E211Q exert approximately 79% of wt ABCG2-mediated methotrexate transport activity, implying that the heterodimer harboring YFP/ABCG2 and E211Q may be able to transport the anticancer drug methotrexate across the biological membranes.
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Affiliation(s)
- Yue-xian Hou
- Department of Biochemistry and Molecular Biology, Mayo Clinic College of Medicine, 13400 East Shea Boulevard, Scottsdale, Arizona 85259, USA
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21
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Seeger MA, van Veen HW. Molecular basis of multidrug transport by ABC transporters. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2009; 1794:725-37. [DOI: 10.1016/j.bbapap.2008.12.004] [Citation(s) in RCA: 106] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/10/2008] [Revised: 12/01/2008] [Accepted: 12/05/2008] [Indexed: 01/15/2023]
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Becker JP, Depret G, Van Bambeke F, Tulkens PM, Prévost M. Molecular models of human P-glycoprotein in two different catalytic states. BMC STRUCTURAL BIOLOGY 2009; 9:3. [PMID: 19159494 PMCID: PMC2661087 DOI: 10.1186/1472-6807-9-3] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/31/2008] [Accepted: 01/22/2009] [Indexed: 12/20/2022]
Abstract
Background P-glycoprotein belongs to the family of ATP-binding cassette proteins which hydrolyze ATP to catalyse the translocation of their substrates through membranes. This protein extrudes a large range of components out of cells, especially therapeutic agents causing a phenomenon known as multidrug resistance. Because of its clinical interest, its activity and transport function have been largely characterized by various biochemical studies. In the absence of a high-resolution structure of P-glycoprotein, homology modeling is a useful tool to help interpretation of experimental data and potentially guide experimental studies. Results We present here three-dimensional models of two different catalytic states of P-glycoprotein that were developed based on the crystal structures of two bacterial multidrug transporters. Our models are supported by a large body of biochemical data. Measured inter-residue distances correlate well with distances derived from cross-linking data. The nucleotide-free model features a large cavity detected in the protein core into which ligands of different size were successfully docked. The locations of docked ligands compare favorably with those suggested by drug binding site mutants. Conclusion Our models can interpret the effects of several mutants in the nucleotide-binding domains (NBDs), within the transmembrane domains (TMDs) or at the NBD:TMD interface. The docking results suggest that the protein has multiple binding sites in agreement with experimental evidence. The nucleotide-bound models are exploited to propose different pathways of signal transmission upon ATP binding/hydrolysis which could lead to the elaboration of conformational changes needed for substrate translocation. We identified a cluster of aromatic residues located at the interface between the NBD and the TMD in opposite halves of the molecule which may contribute to this signal transmission. Our models may characterize different steps in the catalytic cycle and may be important tools to understand the structure-function relationship of P-glycoprotein.
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Affiliation(s)
- Jean-Paul Becker
- Structure et Fonction des Membranes Biologiques, Université Libre de Bruxelles, Boulevard du Triomphe CP 206/2, B-1050 Brussels, Belgium.
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Matsumura Y, Ban N, Inagaki N. Aberrant catalytic cycle and impaired lipid transport into intracellular vesicles in ABCA3 mutants associated with nonfatal pediatric interstitial lung disease. Am J Physiol Lung Cell Mol Physiol 2008; 295:L698-707. [PMID: 18676873 DOI: 10.1152/ajplung.90352.2008] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The ATP-binding cassette transporter ABCA3 mediates uptake of choline-phospholipids into intracellular vesicles and is essential for surfactant metabolism in lung alveolar type II cells. We have shown previously that ABCA3 mutations in fatal surfactant deficiency impair intracellular localization or ATP hydrolysis of ABCA3 protein. However, the mechanisms underlying the less severe phenotype of patients with ABCA3 mutation are unclear. In this study, we characterized ABCA3 mutant proteins identified in pediatric interstitial lung disease (pILD). E292V (intracellular loop 1), E690K (adjacent to Walker B motif in nucleotide binding domain 1), and T1114M (8th putative transmembrane segment) mutant proteins are localized mainly in intracellular vesicle membranes as wild-type protein. Lipid analysis and sucrose gradient fractionation revealed that the transport function of E292V mutant protein is moderately preserved, whereas those of E690K and T1114M mutant proteins are severely impaired. Vanadate-induced nucleotide trapping and photoaffinity labeling of wild-type and mutant proteins using 8-azido-[(32)P]ATP revealed an aberrant catalytic cycle in these mutant proteins. These results demonstrate the importance of a functional catalytic cycle in lipid transport of ABCA3 and suggest a pathophysiological mechanism of pILD due to ABCA3 mutation.
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Affiliation(s)
- Yoshihiro Matsumura
- Deptartment of Diabetes and Clinical Nutrition, Kyoto University, Kyoto 606-8507, Japan
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Structure, function, and evolution of bacterial ATP-binding cassette systems. Microbiol Mol Biol Rev 2008; 72:317-64, table of contents. [PMID: 18535149 DOI: 10.1128/mmbr.00031-07] [Citation(s) in RCA: 926] [Impact Index Per Article: 57.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
SUMMARY ATP-binding cassette (ABC) systems are universally distributed among living organisms and function in many different aspects of bacterial physiology. ABC transporters are best known for their role in the import of essential nutrients and the export of toxic molecules, but they can also mediate the transport of many other physiological substrates. In a classical transport reaction, two highly conserved ATP-binding domains or subunits couple the binding/hydrolysis of ATP to the translocation of particular substrates across the membrane, through interactions with membrane-spanning domains of the transporter. Variations on this basic theme involve soluble ABC ATP-binding proteins that couple ATP hydrolysis to nontransport processes, such as DNA repair and gene expression regulation. Insights into the structure, function, and mechanism of action of bacterial ABC proteins are reported, based on phylogenetic comparisons as well as classic biochemical and genetic approaches. The availability of an increasing number of high-resolution structures has provided a valuable framework for interpretation of recent studies, and realistic models have been proposed to explain how these fascinating molecular machines use complex dynamic processes to fulfill their numerous biological functions. These advances are also important for elucidating the mechanism of action of eukaryotic ABC proteins, because functional defects in many of them are responsible for severe human inherited diseases.
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Abstract
The two NBDs (nucleotide-binding domains) of ABC (ATP-binding-cassette) proteins function in a complex to mediate ATPase activity and this activity has been linked to their regulated transport activity. A similar model has been proposed for CFTR (cystic fibrosis transmembrane conductance regulator), the chloride channel defective in cystic fibrosis, wherein ATP binding and hydrolysis regulate the channel gate. Recently, it was shown that the individual NBDs isolated from CFTR primarily mediate adenylate kinase activity, raising the possibility that this activity may also contribute to gating of the CFTR channel. However, this present study shows that whereas the isolated NBDs exhibit adenylate kinase activity, the full-length purified and reconstituted CFTR protein functions as an ATPase, arguing that the enzymatic activity of the NBDs is dependent on their molecular context and appropriate domain-domain assembly. As expected, the disease-causing mutant bearing a mutation in the ABC signature motif, CFTR-G551D, exhibited a markedly reduced ATPase activity. Furthermore, mutation of the putative catalytic base in CFTR caused a reduction in ATPase activity, with the CFTR-E1371Q mutant supporting a low level of residual activity. Neither of these mutants exhibited detectable adenylate kinase activity. Together, these findings support the concept that the molecular mechanism of action of CFTR is dependent on ATP binding and hydrolysis, and that the structure of prokaryotic ABC ATPases provide a useful template for understanding their mechanism of action.
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Jacquet E, Girard JM, Ramaen O, Pamlard O, Lévaique H, Betton JM, Dassa E, Chesneau O. ATP hydrolysis and pristinamycin IIA inhibition of the Staphylococcus aureus Vga(A), a dual ABC protein involved in streptogramin A resistance. J Biol Chem 2008; 283:25332-25339. [PMID: 18562322 DOI: 10.1074/jbc.m800418200] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
In Gram-positive bacteria, a large subfamily of dual ATP-binding cassette proteins confers acquired or intrinsic resistance to macrolide, lincosamide, and streptogramin antibiotics by a far from well understood mechanism. Here, we report the first biochemical characterization of one such protein, Vga(A), which is involved in streptogramin A (SgA) resistance among staphylococci. Vga(A) is composed of two nucleotide-binding domains (NBDs), separated by a charged linker, with a C-terminal extension and without identified transmembrane domains. Highly purified Vga(A) displays a strong ATPase activity (K(m) = 78 mum, V(m) = 6.8 min(-1)) that was hardly inhibited by orthovanadate. Using mutants of the conserved catalytic glutamate residues, the two NBDs of Vga(A) were shown to contribute unequally to the total ATPase activity, the mutation at NBD2 being more detrimental than the other. ATPase activity of both catalytic sites was essential for Vga(A) biological function because each single Glu mutant was unable to confer SgA resistance in the staphylococcal host. Of great interest, Vga(A) ATPase was specifically inhibited in a non-competitive manner by the SgA substrate, pristinamycin IIA (PIIA). A deletion of the last 18 amino acids of Vga(A) slightly affected the ATPase activity without modifying the PIIA inhibition values. In contrast, this deletion reduced 4-fold the levels of SgA resistance. Altogether, our results suggest a role for the C terminus in regulation of the SgA antibiotic resistance mechanism conferred by Vga(A) and demonstrate that this dual ATP-binding cassette protein interacts directly and specifically with PIIA, its cognate substrate.
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Affiliation(s)
- Eric Jacquet
- Institut de Chimie des Substances Naturelles, CNRS UPR 2301, avenue de la Terrasse, Gif-sur-Yvette 91190 and the.
| | - Jean-Marie Girard
- Institut de Chimie des Substances Naturelles, CNRS UPR 2301, avenue de la Terrasse, Gif-sur-Yvette 91190 and the
| | - Odile Ramaen
- Institut de Chimie des Substances Naturelles, CNRS UPR 2301, avenue de la Terrasse, Gif-sur-Yvette 91190 and the
| | - Olivier Pamlard
- Institut de Chimie des Substances Naturelles, CNRS UPR 2301, avenue de la Terrasse, Gif-sur-Yvette 91190 and the
| | - Hélène Lévaique
- Institut de Chimie des Substances Naturelles, CNRS UPR 2301, avenue de la Terrasse, Gif-sur-Yvette 91190 and the
| | | | - Elie Dassa
- Unité des Membranes Bactériennes, Institut Pasteur, CNRS URA 2172, 25 rue du Docteur Roux, Paris 75724 Cedex 15, France
| | - Olivier Chesneau
- Unité des Membranes Bactériennes, Institut Pasteur, CNRS URA 2172, 25 rue du Docteur Roux, Paris 75724 Cedex 15, France
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Carrier I, Gros P. Investigating the role of the invariant carboxylate residues E552 and E1197 in the catalytic activity of Abcb1a (mouse Mdr3). FEBS J 2008; 275:3312-24. [PMID: 18489584 DOI: 10.1111/j.1742-4658.2008.06479.x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The invariant carboxylate residue which follows the Walker B motif (hyd(4)DE/D) in the nucleotide-binding domains (NBDs) of ATP-binding cassette transporters is thought to be involved in the hydrolysis of the gamma-phosphate of MgATP, either by activating the attacking water molecule or by promoting substrate-assisted catalysis. In Abcb1a, this invariant carboxylate residue corresponds to E552 in NBD1 and E1197 in NBD2. To further characterize the role of these residues in catalysis, we created in Abcb1a the single-site mutants E552D, N and A in NBD1, and E1197D, N and A in NBD2, as well as the double-mutant E552Q/E1197Q. In addition, we created mutants in which the Walker A K --> R mutation known to abolish ATPase activity was introduced in the non-mutant NBD of E552Q and E1197Q. ATPase activity, binding affinity and trapping properties were tested for each Abcb1a variant. The results suggest that the length of the invariant carboxylate residue is important for the catalytic activity, whereas the charge of the side chain is critical for full turnover to occur. Moreover, in the double-mutants where the K --> R mutation is introduced in the 'wild-type' NBD of the E --> Q mutants, single-site turnover is observed, especially when NBD2 can undergo gamma-P(i) cleavage. The results further support the idea that the NBDs are not symmetric and suggest that the invariant carboxylates are involved both in NBD-NBD communication and transition-state formation through orientation of the linchpin residue.
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Affiliation(s)
- Isabelle Carrier
- Department of Biochemistry and McGill Cancer Centre, McGill University, Montreal, Canada
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Sauna ZE, Kim IW, Ambudkar SV. Genomics and the mechanism of P-glycoprotein (ABCB1). J Bioenerg Biomembr 2008; 39:481-7. [PMID: 18058211 DOI: 10.1007/s10863-007-9115-9] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
Abstract
The development of effective clinical interventions against multidrug resistance (MDR) in cancer remains a significant challenge. Single nucleotide polymorphisms (SNPs) contribute to wide variations in how individuals respond to medications and there are several SNPs in human P-glycoprotein (P-gp) that may influence the interactions of drug-substrates with the transporter. Interestingly, even some of the synonymous SNPs have functional consequences for P-gp. It is also becoming increasingly evident that an understanding of the transport pathway of P-gp may be necessary to design effective modulators. In this review we discuss: (1) The potential importance of SNPs (both synonymous and non-synonymous) in MDR and (2) How new concepts that have emerged from structural studies with isolated nucleotide binding domains of bacterial ABC transporters have prompted biochemical studies on P-gp, leading to a better understanding of the mechanism of P-gp mediated transport. Our results suggest that the power-stroke is provided only after formation of the pre-hydrolysis transition-like (E.S) state during ATP hydrolysis.
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Affiliation(s)
- Zuben E Sauna
- Laboratory of Cell Biology, Center for Cancer Research, National Cancer Institute, National Institutes of Health, DHHS, Building 37, 37 Convent Drive, Bethesda, MD 20892-4256, USA
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Cheung JC, Kim Chiaw P, Pasyk S, Bear CE. Molecular basis for the ATPase activity of CFTR. Arch Biochem Biophys 2008; 476:95-100. [PMID: 18417076 DOI: 10.1016/j.abb.2008.03.033] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2008] [Revised: 03/24/2008] [Accepted: 03/26/2008] [Indexed: 12/24/2022]
Abstract
CFTR is a member of the ABC (ATP binding cassette) superfamily of transporters. It is a multidomain membrane protein, which utilizes ATP to regulate the flux of its substrate through the membrane. CFTR is distinct in that it functions as a channel and it possesses a unique regulatory R domain. There has been significant progress in understanding the molecular basis for CFTR activity as an ATPase. The dimeric complex of NBD structures seen in prokaryotic ABC transporters, together with the structure of an isolated CF-NBD1, provide a unifying molecular template to model the structural basis for the ATPase activity of CFTR. The dynamic nature of the interaction between the NBDs and the R domain has been revealed in NMR studies. On the other hand, understanding the mechanisms mediating the transmission of information from the cytosolic domains to the membrane and the channel gate of CFTR remains a central challenge.
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Affiliation(s)
- Joanne C Cheung
- Programme in Molecular Structure & Function, Research Institute, Hospital for Sick Children, 555 University Avenue, Toronto, Ont., Canada
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30
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Lawson J, O'Mara ML, Kerr ID. Structure-based interpretation of the mutagenesis database for the nucleotide binding domains of P-glycoprotein. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2007; 1778:376-91. [PMID: 18035039 DOI: 10.1016/j.bbamem.2007.10.021] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/19/2007] [Revised: 10/12/2007] [Accepted: 10/25/2007] [Indexed: 12/15/2022]
Abstract
P-glycoprotein (P-gp) is the most intensively studied eukaryotic ATP binding cassette (ABC) transporter, due to its involvement in the multidrug resistance phenotype of a number of cancers. In common with most ABC transporters, P-gp is comprised of two transmembrane domains (TMDs) and two nucleotide binding domains (NBD), the latter coupling ATP hydrolysis with substrate transport (efflux in the case of P-gp). Biochemical investigations over the past twenty years have attempted to unlock mechanistic aspects of P-glycoprotein through scanning and site-directed mutagenesis of both the TMDs and the NBDs. Contemporaneously, crystallographers have elucidated the atomic structure of numerous ABC transporter NBDs, as well as the intact structure (i.e. NBDs and TMDs) of a distantly related ABC-exporter Sav1866. Significantly, the structure of P-gp remains unknown, and only low resolution electron microscopy data exists. Within the current manuscript we employ crystallographic data for homologous proteins, and a molecular model for P-gp, to perform a structural interpretation of the existing "mutagenesis database" for P-gp NBDs. Consequently, this will enable testable predictions to be made that will result in further in-roads into our understanding of this clinically important drug pump.
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Affiliation(s)
- J Lawson
- School of Biomedical Sciences, University of Nottingham, Queen's Medical Centre, Nottingham, NG7 2UH, UK
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31
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Degiorgio D, Colombo C, Seia M, Porcaro L, Costantino L, Zazzeron L, Bordo D, Coviello DA. Molecular characterization and structural implications of 25 new ABCB4 mutations in progressive familial intrahepatic cholestasis type 3 (PFIC3). Eur J Hum Genet 2007; 15:1230-8. [PMID: 17726488 DOI: 10.1038/sj.ejhg.5201908] [Citation(s) in RCA: 74] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Progressive familial intrahepatic cholestasis type 3 (PFIC3) is an autosomal-recessive disorder due to mutations in the ATP-binding cassette, subfamily B, member 4 gene (ABCB4). ABCB4 is the liver-specific membrane transporter of phosphatidylcholine, a major and exclusive component of mammalian bile. The disease is characterized by early onset of cholestasis with high serum gamma-glutamyltranspeptidase activity, which progresses into cirrhosis and liver failure before adulthood. Presently, about 20 distinct ABCB4 mutations associated to PFIC3 have been described. We report the molecular characterization of 68 PFIC3 index cases enrolled in a multicenter study, which represents the largest cohort of PFIC3 patients screened for ABCB4 mutations to date. We observed 31 mutated ABCB4 alleles in 18 index cases with 29 distinct mutations, 25 of which are novel. Despite the lack of structural information on the ABCB4 protein, the elucidation of the three-dimensional structure of bacterial homolog allows the three-dimensional model of ABCB4 to be built by homology modeling and the position of the mutated amino-acids in the protein tertiary structure to be located. In a significant fraction of the cases reported in this study, the mutation should result in substantial impairment of ABCB4 floppase activity. The results of this study provide evidence of the broad allelic heterogeneity of the disease, with causative mutations spread along 14 of the 27 coding exons, but with higher prevalence on exon 17 that, as recently shown for the closely related paralogous ABCB1 gene, could contain an evolutionary marker for mammalian ABCB4 genes in the seventh transmembrane segment.
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Affiliation(s)
- Dario Degiorgio
- Laboratorio di Genetica Medica, Fondazione IRCCS, Ospedale Maggiore Policlinico, Mangiagalli e Regina Elena, Milano, Italy
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32
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Chang XB. A molecular understanding of ATP-dependent solute transport by multidrug resistance-associated protein MRP1. Cancer Metastasis Rev 2007; 26:15-37. [PMID: 17295059 DOI: 10.1007/s10555-007-9041-7] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Over a million new cases of cancers are diagnosed each year in the United States and over half of these patients die from these devastating diseases. Thus, cancers cause a major public health problem in the United States and worldwide. Chemotherapy remains the principal mode to treat many metastatic cancers. However, occurrence of cellular multidrug resistance (MDR) prevents efficient killing of cancer cells, leading to chemotherapeutic treatment failure. Numerous mechanisms of MDR exist in cancer cells, such as intrinsic or acquired MDR. Overexpression of ATP-binding cassette (ABC) drug transporters, such as P-glycoprotein (P-gp or ABCB1), breast cancer resistance protein (BCRP or ABCG2) and/or multidrug resistance-associated protein (MRP1 or ABCC1), confers an acquired MDR due to their capabilities of transporting a broad range of chemically diverse anticancer drugs. In addition to their roles in MDR, there is substantial evidence suggesting that these drug transporters have functions in tissue defense. Basically, these drug transporters are expressed in tissues important for absorption, such as in lung and gut, and for metabolism and elimination, such as in liver and kidney. In addition, these drug transporters play an important role in maintaining the barrier function of many tissues including blood-brain barrier, blood-cerebral spinal fluid barrier, blood-testis barrier and the maternal-fetal barrier. Thus, these ATP-dependent drug transporters play an important role in the absorption, disposition and elimination of the structurally diverse array of the endobiotics and xenobiotics. In this review, the molecular mechanism of ATP-dependent solute transport by MRP1 will be addressed.
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Affiliation(s)
- Xiu-bao Chang
- Mayo Clinic College of Medicine, Scottsdale, AZ 85259, USA.
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33
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Daus ML, Grote M, Müller P, Doebber M, Herrmann A, Steinhoff HJ, Dassa E, Schneider E. ATP-driven MalK dimer closure and reopening and conformational changes of the "EAA" motifs are crucial for function of the maltose ATP-binding cassette transporter (MalFGK2). J Biol Chem 2007; 282:22387-96. [PMID: 17545154 DOI: 10.1074/jbc.m701979200] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
We have investigated conformational changes of the purified maltose ATP-binding cassette transporter (MalFGK(2)) upon binding of ATP. The transport complex is composed of a heterodimer of the hydrophobic subunits MalF and MalG constituting the translocation pore and of a homodimer of MalK, representing the ATP-hydrolyzing subunit. Substrate is delivered to the transporter in complex with periplasmic maltose-binding protein (MalE). Cross-linking experiments with a variant containing an A85C mutation within the Q-loop of each MalK monomer indicated an ATP-induced shortening of the distance between both monomers. Cross-linking caused a substantial inhibition of MalE-maltose-stimulated ATPase activity. We further demonstrated that a mutation affecting the "catalytic carboxylate" (E159Q) locks the MalK dimer in the closed state, whereas a transporter containing the "ABC signature" mutation Q140K permanently resides in the resting state. Cross-linking experiments with variants containing the A85C mutation combined with cysteine substitutions in the conserved EAA motifs of MalF and MalG, respectively, revealed close proximity of these residues in the resting state. The formation of a MalK-MalG heterodimer remained unchanged upon the addition of ATP, indicating that MalG-EAA moves along with MalK during dimer closure. In contrast, the yield of MalK-MalF dimers was substantially reduced. This might be taken as further evidence for asymmetric functions of both EAA motifs. Cross-linking also caused inhibition of ATPase activity, suggesting that transporter function requires conformational changes of both EAA motifs. Together, our data support ATP-driven MalK dimer closure and reopening as crucial steps in the translocation cycle of the intact maltose transporter and are discussed with respect to a current model.
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Affiliation(s)
- Martin L Daus
- Institut für Biologie/Bakterienphysiologie, Humboldt Universität zu Berlin, Chausseestrasse 117, D-10115 Berlin, Germany
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Macdonald N, Gledhill A. Potential impact of ABCB1 (p-glycoprotein) polymorphisms on avermectin toxicity in humans. Arch Toxicol 2007; 81:553-63. [PMID: 17354009 DOI: 10.1007/s00204-007-0193-6] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2006] [Accepted: 02/13/2007] [Indexed: 01/18/2023]
Abstract
Several members of the ATP binding cassette (ABC) transporter protein superfamily perform xenobiotic efflux functions in mammals, limiting gut absorption, mediating excretion, and controlling entry of a wide range of chemicals to sensitive compartments such as brain, testes and foetus. Perhaps the best characterised of these is p-glycoprotein (gene name ABCB1/MDR1), a barrier epithelia expressed protein with structurally diverse substrates, including the avermectin pesticides. In specific mouse and dog strains, ABCB1 mutations have been identified that result in loss of p-glycoprotein function in the blood brain barrier (BBB) and increased susceptibility to avermectin neurotoxicity. As yet no large rearrangements of the human ABCB1 gene analogous to those in the mouse and dog have been identified. However, numerous human ABCB1 single nucleotide polymorphisms (SNPs) have been identified, the allelic frequencies of which vary with ethnicity. There is no clear consensus on whether or not SNPs, or combinations of SNPs, reduce human p-glycoprotein functionality. However, recent in vivo human data indicate that the two commonest ABCB1 haplotypes both exhibit full BBB functionality. We discuss here the role of p-glycoprotein in limiting brain absorption of avermectin pesticides, as well as the potential impact of the reported functional effects and population frequencies of known ABCB1 polymorphisms on avermectin pesticide risk assessments.
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Affiliation(s)
- Neil Macdonald
- Syngenta Central Toxicology Laboratory, Alderley Park, Macclesfield, SK10 4TJ, UK
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35
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Kerr ID, Bennett MJ. New insight into the biochemical mechanisms regulating auxin transport in plants. Biochem J 2007; 401:613-22. [PMID: 17209803 PMCID: PMC1770846 DOI: 10.1042/bj20061411] [Citation(s) in RCA: 70] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
The transport of the plant hormone auxin has been under intense investigation since its identification 80 years ago. Studies have gradually refined our understanding of the importance of auxin transport in many aspects of plant signalling and development, and the focus has intensified in recent years towards the identification of the proteins involved in auxin transport and their functional mechanism. Within the past 18 months, the field has progressed rapidly, with confirmation that several distinct classes of proteins, previously dubbed as 'putative auxin permeases' or 'auxin transport facilitators', are bona fide transporters of IAA (indol-3-ylacetic acid). In this review we will appraise the recent transport data and highlight likely future research directions, including the characterization of auxiliary proteins necessary for the regulation of auxin transporters.
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Affiliation(s)
- Ian D Kerr
- School of Biomedical Sciences, University of Nottingham, Queen's Medical Centre, Nottingham NG7 2UH, UK.
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36
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Rai V, Gaur M, Shukla S, Shukla S, Ambudkar SV, Komath SS, Prasad R. Conserved Asp327 of walker B motif in the N-terminal nucleotide binding domain (NBD-1) of Cdr1p of Candida albicans has acquired a new role in ATP hydrolysis. Biochemistry 2007; 45:14726-39. [PMID: 17144665 PMCID: PMC2526123 DOI: 10.1021/bi061535t] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
The Walker A and B motifs of nucleotide binding domains (NBDs) of Cdr1p though almost identical to all ABC transporters, has unique substitutions. We have shown in the past that Trp326 of Walker B and Cys193 of Walker A motifs of N-terminal NBD of Cdr1p have distinct roles in ATP binding and hydrolysis, respectively. In the present study, we have examined the role of a well conserved Asp327 in the Walker B motif of the N-terminal NBD, which is preceded (Trp326) and followed (Asn328) by atypical amino acid substitutions and compared it with its equivalent well conserved Asp1026 of the C-terminal NBD of Cdr1p. We observed that the removal of the negative charge by D327N, D327A, D1026N, D1026A, and D327N/D1026N substitutions, resulted in Cdr1p mutant variants that were severely impaired in ATPase activity and drug efflux. Importantly, all of the mutant variants showed characteristics similar to those of the wild type with respect to cell surface expression and photoaffinity drug analogue [125I] IAAP and [3H] azidopine labeling. Although the Cdr1p D327N mutant variant showed comparable binding with [alpha-32P] 8-azido ATP, Cdr1p D1026N and Cdr1p D327N/D1026N mutant variants were crippled in nucleotide binding. That the two conserved carboxylate residues Asp327 and Asp1026 are functionally different was further evident from the pH profile of ATPase activity. The Cdr1p D327N mutant variant showed approximately 40% enhancement of its residual ATPase activity at acidic pH, whereas no such pH effect was seen with the Cdr1p D1026N mutant variant. Our experimental data suggest that Asp327 of N-terminal NBD has acquired a new role to act as a catalytic base in ATP hydrolysis, a role normally conserved for Glu present adjacent to the conserved Asp in the Walker B motif of all the non-fungal transporters.
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Affiliation(s)
- Versha Rai
- Membrane Biology Laboratory, School of Life Sciences, Jawaharlal Nehru University, New Delhi, 110067, INDIA
| | - Manisha Gaur
- Membrane Biology Laboratory, School of Life Sciences, Jawaharlal Nehru University, New Delhi, 110067, INDIA
| | - Sudhanshu Shukla
- Membrane Biology Laboratory, School of Life Sciences, Jawaharlal Nehru University, New Delhi, 110067, INDIA
| | - Suneet Shukla
- Laboratory of Cell Biology, Center for Cancer Research, National Cancer Institute, National Institute of Health, Bethesda, Maryland, 20892-4254, USA
| | - Suresh V. Ambudkar
- Laboratory of Cell Biology, Center for Cancer Research, National Cancer Institute, National Institute of Health, Bethesda, Maryland, 20892-4254, USA
| | - Sneha Sudha Komath
- Biophysical Chemistry Laboratory, School of Life Sciences, Jawaharlal Nehru University, New Delhi, 110067, INDIA
| | - Rajendra Prasad
- Membrane Biology Laboratory, School of Life Sciences, Jawaharlal Nehru University, New Delhi, 110067, INDIA
- Corresponding author: E-mail: ; Telephone: 91-11-26704509; Fax: 91-11-26717081
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37
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Carrier I, Urbatsch IL, Senior AE, Gros P. Mutational analysis of conserved aromatic residues in the A-loop of the ABC transporter ABCB1A (mouse Mdr3). FEBS Lett 2007; 581:301-8. [PMID: 17214987 DOI: 10.1016/j.febslet.2006.12.030] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2006] [Accepted: 12/15/2006] [Indexed: 11/29/2022]
Abstract
The A-loop is a recently described conserved region in the NBDs of ABC transporters [Ambudkar, S.V., Kim, I.-W., Xia, D. and Sauna, Z.E. (2006) The A-loop, a novel conserved aromatic acid subdomain upstream of the Walker A motif in ABC transporters, is critical for ATP binding. FEBS Lett. 580, 1049-1055; Kim, I.W., Peng, X.H., Sauna, Z.E., FitzGerald, P.C., Xia, D., Muller, M., Nandigama, K. and Ambudkar, S.V. (2006) The conserved tyrosine residues 401 and 1044 in ATP sites of human P-glycoprotein are critical for ATP binding and hydrolysis: evidence for a conserved subdomain, the A-loop in the ATP-binding cassette. Biochemistry 45, 7605-7616]. In mouse P-glycoprotein (Abcb1a), the aromatic residue of the A-loop in both NBDs is a tyrosine: Y397 in NBD1 and Y1040 in NBD2. Another tyrosine residue (618 in NBD1 and 1263 in NBD2) also appears to lie in proximity to the ATP molecule. We have mutated residues Y397, Y618, Y1040, and Y1263 to tryptophan and analyzed the effect of these substitutions on transport properties, ATP binding, and ATP hydrolysis by Abcb1a (mouse Mdr3). Y618W and Y1263W enzymes had catalytic characteristics similar to WT Abcb1a. On the other hand, Y397W and Y1040W showed impaired transport and greatly reduced ATPase activity, including a approximately 10-fold increase in Km for MgATP. Thus, Y397 and Y1040 play an important role in Abcb1a catalysis.
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Affiliation(s)
- Isabelle Carrier
- Department of Biochemistry and McGill Cancer Centre, McGill University, McIntyre Medical Sciences Building, Room 907, 3655 Sir William Osler Drive, Montréal, Que., Canada H3G 1Y6
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38
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Perria CL, Rajamanickam V, Lapinski PE, Raghavan M. Catalytic site modifications of TAP1 and TAP2 and their functional consequences. J Biol Chem 2006; 281:39839-51. [PMID: 17068338 DOI: 10.1074/jbc.m605492200] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The transporter associated with antigen processing (TAP), a member of the ATP binding cassette (ABC) family of transmembrane transporters, transports peptides across the endoplasmic reticulum membrane for assembly of major histocompatibility complex class I molecules. Two subunits, TAP1 and TAP2, are required for peptide transport, and ATP hydrolysis by TAP1.TAP2 complexes is important for transport activity. Two nucleotide binding sites are present in TAP1.TAP2 complexes. Compared with other ABC transporters, the first nucleotide binding site contains non-consensus catalytic site residues, including Asp(668) in the Walker B region of TAP1 (in place of a highly conserved glutamic acid), and Gln(701) in the switch region of TAP1 (in place of a highly conserved histidine). At the second nucleotide binding site, a glutamic acid (TAP2 Glu(632)) follows the Walker B motif, and the switch region contains a histidine (TAP2 His(661)). We found that alterations at Glu(632) and His(661) of TAP2 significantly reduced peptide translocation and/or TAP-induced major histocompatibility complex class I surface expression. Alterations of TAP1 Asp(668) alone or in combination with TAP1 Gln(701) had only small effects on TAP activity. Thus, the naturally occurring Asp(668) and Gln(701) alterations of TAP1 are likely to contribute to attenuated catalytic activity at the first nucleotide binding site (the TAP1 site) of TAP complexes. Due to its enhanced catalytic activity, the second nucleotide binding site (the TAP2 site) appears to be the main site driving peptide transport. A mechanistic model involving one main active site is likely to apply to other ABC transporters that have an asymmetric distribution of catalytic site residues within the two nucleotide binding sites.
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Affiliation(s)
- Christopher L Perria
- Department of Microbiology and Immunology, University of Michigan Medical School, Ann Arbor, Michigan 48109-0620, USA
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Ernst R, Koch J, Horn C, Tampé R, Schmitt L. Engineering ATPase Activity in the Isolated ABC Cassette of Human TAP1. J Biol Chem 2006; 281:27471-80. [PMID: 16864587 DOI: 10.1074/jbc.m601131200] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023] Open
Abstract
The human transporter associated with antigen processing (TAP) translocates antigenic peptides from the cytosol into the endoplasmic reticulum lumen. The functional unit of TAP is a heterodimer composed of the TAP1 and TAP2 subunits, both of which are members of the ABC-transporter family. ABC-transporters are ATP-dependent pumps, channels, or receptors that are composed of four modules: two nucleotide-binding domains (NBDs) and two transmembrane domains (TMDs). Although the TMDs are rather divergent in sequence, the NBDs are conserved with respect to structure and function. Interestingly, the NBD of TAP1 contains mutations at amino acid positions that have been proposed to be essential for catalytic activity. Instead of a glutamate, proposed to act as a general base, TAP1 contains an aspartate and a glutamine instead of the conserved histidine, which has been suggested to act as the linchpin. We used this degeneration to evaluate the individual contribution of these two amino acids to the ATPase activity of the engineered TAP1-NBD mutants. Based on our results a catalytic hierarchy of these two fundamental amino acids in ATP hydrolysis of the mutated TAP1 motor domain was deduced.
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Affiliation(s)
- Robert Ernst
- Institute of Biochemistry, Heinrich Heine University Duesseldorf, Universitaetsstrasse 1, 40225 Duesseldorf, Germany
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40
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Deeley RG, Westlake C, Cole SPC. Transmembrane transport of endo- and xenobiotics by mammalian ATP-binding cassette multidrug resistance proteins. Physiol Rev 2006; 86:849-99. [PMID: 16816140 DOI: 10.1152/physrev.00035.2005] [Citation(s) in RCA: 533] [Impact Index Per Article: 29.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Multidrug Resistance Proteins (MRPs), together with the cystic fibrosis conductance regulator (CFTR/ABCC7) and the sulfonylurea receptors (SUR1/ABCC8 and SUR2/ABCC9) comprise the 13 members of the human "C" branch of the ATP binding cassette (ABC) superfamily. All C branch proteins share conserved structural features in their nucleotide binding domains (NBDs) that distinguish them from other ABC proteins. The MRPs can be further divided into two subfamilies "long" (MRP1, -2, -3, -6, and -7) and "short" (MRP4, -5, -8, -9, and -10). The short MRPs have a typical ABC transporter structure with two polytropic membrane spanning domains (MSDs) and two NBDs, while the long MRPs have an additional NH2-terminal MSD. In vitro, the MRPs can collectively confer resistance to natural product drugs and their conjugated metabolites, platinum compounds, folate antimetabolites, nucleoside and nucleotide analogs, arsenical and antimonial oxyanions, peptide-based agents, and, under certain circumstances, alkylating agents. The MRPs are also primary active transporters of other structurally diverse compounds, including glutathione, glucuronide, and sulfate conjugates of a large number of xeno- and endobiotics. In vivo, several MRPs are major contributors to the distribution and elimination of a wide range of both anticancer and non-anticancer drugs and metabolites. In this review, we describe what is known of the structure of the MRPs and the mechanisms by which they recognize and transport their diverse substrates. We also summarize knowledge of their possible physiological functions and evidence that they may be involved in the clinical drug resistance of various forms of cancer.
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Affiliation(s)
- Roger G Deeley
- Division of Cancer Biology and Genetics, Cancer Research Institute and Department of Biochemistry, Queen's University Kingdom, Ontario, Canada.
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41
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Shilling RA, Venter H, Velamakanni S, Bapna A, Woebking B, Shahi S, van Veen HW. New light on multidrug binding by an ATP-binding-cassette transporter. Trends Pharmacol Sci 2006; 27:195-203. [PMID: 16545467 DOI: 10.1016/j.tips.2006.02.008] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2005] [Revised: 11/23/2005] [Accepted: 02/22/2006] [Indexed: 11/26/2022]
Abstract
ATP-binding-cassette (ABC) multidrug transporters confer multidrug resistance to pathogenic microorganisms and human tumour cells by mediating the extrusion of structurally unrelated chemotherapeutic drugs from the cell. The molecular basis by which ABC multidrug transporters bind and transport drugs is far from clear. Genetic analyses during the past 14 years reveal that the replacement of many individual amino acids in mammalian multidrug resistance P-glycoproteins can affect cellular resistance to drugs, but these studies have failed to identify specific regions in the primary amino acid sequence that are part of a defined drug-binding pocket. The recent publication of an X-ray crystallographic structure of the bacterial P-glycoprotein homologue MsbA and an MsbA-based homology model of human P-glycoprotein creates an opportunity to compare the original mutagenesis data with the three-dimensional structures of transporters. Our comparisons reveal that mutations that alter specificity are present in three-dimensional 'hotspot' regions in the membrane domains of P-glycoprotein.
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MESH Headings
- ATP Binding Cassette Transporter, Subfamily B, Member 1/chemistry
- ATP Binding Cassette Transporter, Subfamily B, Member 1/genetics
- ATP Binding Cassette Transporter, Subfamily B, Member 1/metabolism
- ATP-Binding Cassette Transporters/chemistry
- ATP-Binding Cassette Transporters/genetics
- ATP-Binding Cassette Transporters/metabolism
- Amino Acid Sequence
- Animals
- Antineoplastic Agents/metabolism
- Binding Sites/genetics
- Biological Transport
- Drug Resistance, Multiple
- Drug Resistance, Neoplasm
- Humans
- Models, Molecular
- Molecular Sequence Data
- Mutation
- Protein Structure, Tertiary
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Affiliation(s)
- Richard A Shilling
- Department of Pharmacology, University of Cambridge, Tennis Court Road, Cambridge, UK, CB2 1PD
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42
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Oswald C, Holland IB, Schmitt L. The motor domains of ABC-transporters. What can structures tell us? Naunyn Schmiedebergs Arch Pharmacol 2006; 372:385-99. [PMID: 16541253 DOI: 10.1007/s00210-005-0031-4] [Citation(s) in RCA: 104] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2005] [Accepted: 12/19/2005] [Indexed: 01/21/2023]
Abstract
The transport of substrates across a cellular membrane is a vitally important biological function essential for cell survival. ATP-binding cassette (ABC) transporters constitute one of the largest subfamilies of membrane proteins, accomplishing this task. Mutations in genes encoding for ABC transporters cause different diseases, for example, Adrenoleukodystrophy, Stargardt disease or Cystic Fibrosis. Furthermore, some ABC transporters are responsible for multidrug resistance, presenting a major obstacle in modern cancer chemotherapy. In order to translocate the enormous variety of substrates, ranging from ions, nutrients, small peptides to large toxins, different ABC-transporters utilize the energy gained from ATP binding and hydrolysis. The ATP binding cassette, also called the motor domain of ABC transporters, is highly conserved among all ABC transporters. The ability to purify this domain rather easily presents a perfect possibility to investigate the mechanism of ATP hydrolysis, thus providing us with a detailed picture of this process. Recently, many crystal structures of the ATP-binding domain and the full-length structures of two ABC transporters have been solved. Combining these structural data, we have now the opportunity to analyze the hydrolysis event on a molecular level. This review provides an overview of the structural investigations of the ATP-binding domains, highlighting molecular changes upon ATP binding and hydrolysis.
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Affiliation(s)
- Christine Oswald
- Institute of Biochemistry, Heinrich Heine University Duesseldorf, Universitaetsstr. 1, 40225, Duesseldorf, Germanye
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43
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Frelet A, Klein M. Insight in eukaryotic ABC transporter function by mutation analysis. FEBS Lett 2006; 580:1064-84. [PMID: 16442101 DOI: 10.1016/j.febslet.2006.01.024] [Citation(s) in RCA: 63] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2005] [Revised: 01/10/2006] [Accepted: 01/10/2006] [Indexed: 11/21/2022]
Abstract
With regard to structure-function relations of ATP-binding cassette (ABC) transporters several intriguing questions are in the spotlight of active research: Why do functional ABC transporters possess two ATP binding and hydrolysis domains together with two ABC signatures and to what extent are the individual nucleotide-binding domains independent or interacting? Where is the substrate-binding site and how is ATP hydrolysis functionally coupled to the transport process itself? Although much progress has been made in the elucidation of the three-dimensional structures of ABC transporters in the last years by several crystallographic studies including novel models for the nucleotide hydrolysis and translocation catalysis, site-directed mutagenesis as well as the identification of natural mutations is still a major tool to evaluate effects of individual amino acids on the overall function of ABC transporters. Apart from alterations in characteristic sequence such as Walker A, Walker B and the ABC signature other parts of ABC proteins were subject to detailed mutagenesis studies including the substrate-binding site or the regulatory domain of CFTR. In this review, we will give a detailed overview of the mutation analysis reported for selected ABC transporters of the ABCB and ABCC subfamilies, namely HsCFTR/ABCC7, HsSUR/ABCC8,9, HsMRP1/ABCC1, HsMRP2/ABCC2, ScYCF1 and P-glycoprotein (Pgp)/MDR1/ABCB1 and their effects on the function of each protein.
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Affiliation(s)
- Annie Frelet
- Zurich Basel Plant Science Center, University of Zurich, Plant Biology, Zollikerstrasse 107, CH-8008 Zurich, Switzerland
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44
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Ambudkar SV, Kim IW, Xia D, Sauna ZE. The A-loop, a novel conserved aromatic acid subdomain upstream of the Walker A motif in ABC transporters, is critical for ATP binding. FEBS Lett 2005; 580:1049-55. [PMID: 16412422 DOI: 10.1016/j.febslet.2005.12.051] [Citation(s) in RCA: 134] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2005] [Revised: 12/13/2005] [Accepted: 12/14/2005] [Indexed: 11/23/2022]
Abstract
ATP-binding cassette (ABC) transporters represent one of the largest families of proteins, and transport a variety of substrates ranging from ions to amphipathic anticancer drugs. The functional unit of an ABC transporter is comprised of two transmembrane domains and two cytoplasmic ABC ATPase domains. The energy of the binding and hydrolysis of ATP is used to transport the substrates across membranes. An ABC domain consists of conserved regions, the Walker A and B motifs, the signature (or C) region and the D, H and Q loops. We recently described the A-loop (Aromatic residue interacting with the Adenine ring of ATP), a highly conserved aromatic residue approximately 25 amino acids upstream of the Walker A motif that is essential for ATP-binding. Here, we review the mutational analysis of this subdomain in human P-glycoprotein as well as homology modeling, structural and data mining studies that provide evidence for a functional role of the A-loop in ATP-binding in most members of the superfamily of ABC transporters.
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Affiliation(s)
- Suresh V Ambudkar
- Laboratory of Cell Biology, Center for Cancer Research, National Cancer Institute, National Institutes of Health, DHHS, Bethesda, MD 20892-4256, USA.
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Abstract
MDR1 (once P-glycoprotein, now referred to as ABCB1) plays a role as a blood-brain barrier, preventing drug absorption into the brain, and is known to confer multiple drug resistance in cancer chemotherapy. MDR1 is composed of two repeated fragments, and there are six transmembrane domains (TMD) on the N-terminal of each repeat and a nucleotide (ATP) binding domain (NBD) on the C-terminal. These two repeats are dependent but cooperate as one functional molecule, with one pocket for excreting drugs. The 12 TM domains form a funnel facing the outside of cells, and NBD is in cytosol as a dimer. One NBD is composed of the Walker A, Q-loop, ABC-signature and the Walker B for phosphate binding of nucleotide. This tertiary structure of MDR1 is suggested from the structure of the NBD of histidine permease (HisP), clarified by x-ray crystallography. On the model of HisP, the NBD positions described above make a functional domain, and the same NBD structure is found on many other ABC transporters. An experiment with MDR1 gene knockout mice showed the high plasma AUC of drugs in mdr null mice [mdr1a(-/-)] and a high level in the brain, indicating that MDR1 has an efflux function (prevention of absorption) in the intestinal lumen and acts as a barrier of drug uptake in the brain, as well as has the function of urinary and biliary excretion of drugs. The transcription of MDR1 is dependent on two sites; the promoter site (-105/-100)(-245/-141) and the enhancer site (-7864/-7817). Autoantibody from autoimmune hepatitis patients weakly reacted with the extracellular peptide (aa314-aa328 between TM5 and 6) of MDR1 on the outside of the cell membrane, and did not react with peptides in the NBD and in the membrane-spanning region in TM5. There is an ambiguity about the function of MDR1 as GlcCer translocase.
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Affiliation(s)
- Takaharu Mizutani
- Graduate School of Pharmaceutical Sciences, Nagoya City University, Nagoya, Japan.
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Ambudkar SV, Kim IW, Sauna ZE. The power of the pump: mechanisms of action of P-glycoprotein (ABCB1). Eur J Pharm Sci 2005; 27:392-400. [PMID: 16352426 DOI: 10.1016/j.ejps.2005.10.010] [Citation(s) in RCA: 137] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2005] [Accepted: 10/28/2005] [Indexed: 12/27/2022]
Abstract
Members of the superfamily of ATP-binding cassette (ABC) transporters mediate the movement of a variety of substrates including simple ions, complex lipids and xenobiotics. At least 18 ABC transport proteins are associated with disease conditions. P-glycoprotein (Pgp, ABCB1) is the archetypical mammalian ABC transport protein and its mechanism of action has received considerable attention. There is strong biochemical evidence that Pgp moves molecular cargo against a concentration gradient using the energy of ATP hydrolysis. However, the molecular details of how the energy of ATP hydrolysis is coupled to transport remain in dispute and it has not been possible to reconcile the data from various laboratories into a single model. The functional unit of Pgp consists of two nucleotide binding domains (NBDs) and two trans-membrane domains which are involved in the transport of drug substrates. Considerable progress has been made in recent years in characterizing these functionally and spatially distinct domains of Pgp. In addition, our understanding of the domains has been augmented by the resolution of structures of several non-mammalian ABC proteins. This review considers: (i) the role of specific conserved amino acids in ATP hydrolysis mediated by Pgp; (ii) emerging insights into the dimensions of the drug binding pocket and the interactions between Pgp and the transport substrates and (iii) our current understanding of the mechanisms of coupling between energy derived from ATP binding and/or hydrolysis and efflux of drug substrates.
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Affiliation(s)
- Suresh V Ambudkar
- Laboratory of Cell Biology, Center for Cancer Research, National Cancer Institute, National Institutes of Health, DHHS, Bethesda, MD 20892-4256, USA.
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Daus ML, Landmesser H, Schlosser A, Müller P, Herrmann A, Schneider E. ATP induces conformational changes of periplasmic loop regions of the maltose ATP-binding cassette transporter. J Biol Chem 2005; 281:3856-65. [PMID: 16352608 DOI: 10.1074/jbc.m511953200] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
We have studied cofactor-induced conformational changes of the maltose ATP-binding cassette transporter by employing limited proteolysis in detergent solution. The transport complex consists of one copy each of the transmembrane subunits, MalF and MalG, and of two copies of the nucleotide-binding subunit, MalK. Transport activity further requires the periplasmic maltose-binding protein, MalE. Binding of ATP to the MalK subunits increased the susceptibility of two tryptic cleavage sites in the periplasmic loops P2 of MalF and P1 of MalG, respectively. Lys(262) of MalF and Arg(73) of MalG were identified as probable cleavage sites, resulting in two N-terminal peptide fragments of 29 and 8 kDa, respectively. Trapping the complex in the transition state by vanadate further stabilized the fragments. In contrast, the tryptic cleavage profile of MalK remained largely unchanged. ATP-induced conformational changes of MalF-P2 and MalG-P1 were supported by fluorescence spectroscopy of complex variants labeled with 2-(4'-maleimidoanilino)naphthalene-6-sulfonic acid. Limited proteolysis was subsequently used as a tool to study the consequences of mutations on the transport cycle. The results suggest that complex variants exhibiting a binding protein-independent phenotype (MalF500) or containing a mutation that affects the "catalytic carboxylate" (MalKE159Q) reside in a transition state-like conformation. A similar conclusion was drawn for a complex containing a replacement of MalKQ140 in the signature sequence by leucine, whereas substitution of lysine for Gln(140) appears to lock the transport complex in the ground state. Together, our data provide the first evidence for conformational changes of the transmembrane subunits of an ATP-binding cassette import system upon binding of ATP.
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Affiliation(s)
- Martin L Daus
- Institut für Biologie/Bakterienphysiologie, Humboldt Universität zu Berlin, Germany
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48
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Hanekop N, Zaitseva J, Jenewein S, Holland IB, Schmitt L. Molecular insights into the mechanism of ATP-hydrolysis by the NBD of the ABC-transporter HlyB. FEBS Lett 2005; 580:1036-41. [PMID: 16330029 DOI: 10.1016/j.febslet.2005.11.012] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2005] [Revised: 11/03/2005] [Accepted: 11/04/2005] [Indexed: 02/08/2023]
Abstract
The ABC-transporter HlyB is a central element of the Type I protein secretion machinery, dedicated to export the E. coli toxin HlyA in a single step across the two membranes of the cell envelope. Here, we discuss recent insights into the structure and the mechanism of ATP-hydrolysis by the NBD of HlyB. Combining structural and biochemical data, we have suggested that substrate-assisted catalysis (SAC), but not general base catalysis, is responsible for ATP-hydrolysis in this NBD and might also operate in other NBDs. Finally, the implications and advantages of SAC are discussed in the context of ATP-induced dimerization of the NBDs.
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Affiliation(s)
- N Hanekop
- Institute of Biochemistry, Heinrich Heine University Duesseldorf, Universitaetsstr. 1, 40225 Duesseldorf, Germany
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49
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A molecular understanding of the catalytic cycle of the nucleotide-binding domain of the ABC transporter HlyB. Biochem Soc Trans 2005. [DOI: 10.1042/bst0330990] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
The ABC transporter (ATP-binding-cassette transporter) HlyB (haemolysin B) is the central element of a type I secretion machinery, dedicated to the secretion of the toxin HlyA in Escherichia coli. In addition to the ABC transporter, two other indispensable elements are necessary for the secretion of the toxin across two membranes in a single step: the transenvelope protein HlyD and the outer membrane protein TolC. Despite the fact that the hydrolysis of ATP by HlyB fuels secretion of HlyA, the essential features of the underlying transport mechanism remain an enigma. Similar to all other ABC transporters, ranging from bacteria to man, HlyB is composed of two NBDs (nucleotide-binding domains) and two transmembrane domains. Here we summarize our detailed biochemical, biophysical and structural studies aimed at an understanding of the molecular principles of how ATP-hydrolysis is coupled to energy transduction, including the conformational changes occurring during the catalytic cycle, leading to substrate transport. We have obtained individual crystal structures for each single ground state of the catalytic cycle. From these and other biochemical and mutational studies, we shall provide a detailed molecular picture of the steps governing intramolecular communication and the utilization of chemical energy, due to ATP hydrolysis, in relation to resulting structural changes within the NBD. These data will be summarized in a general model to explain how these molecular machines achieve translocation of molecules across biological membranes.
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50
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Zaitseva J, Jenewein S, Jumpertz T, Holland IB, Schmitt L. H662 is the linchpin of ATP hydrolysis in the nucleotide-binding domain of the ABC transporter HlyB. EMBO J 2005; 24:1901-10. [PMID: 15889153 PMCID: PMC1142601 DOI: 10.1038/sj.emboj.7600657] [Citation(s) in RCA: 290] [Impact Index Per Article: 15.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2004] [Accepted: 03/23/2005] [Indexed: 01/07/2023] Open
Abstract
The ABC transporter HlyB is a central element of the HlyA secretion machinery, a paradigm of Type I secretion. Here, we describe the crystal structure of the HlyB-NBD (nucleotide-binding domain) with H662 replaced by Ala in complex with ATP/Mg2+. The dimer shows a composite architecture, in which two intact ATP molecules are bound at the interface of the Walker A motif and the C-loop, provided by the two monomers. ATPase measurements confirm that H662 is essential for activity. Based on these data, we propose a model in which E631 and H662, highly conserved among ABC transporters, form a catalytic dyad. Here, H662 acts as a 'linchpin', holding together all required parts of a complicated network of interactions between ATP, water molecules, Mg2+, and amino acids both in cis and trans, necessary for intermonomer communication. Based on biochemical experiments, we discuss the hypothesis that substrate-assisted catalysis, rather than general base catalysis might operate in ABC-ATPases.
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Affiliation(s)
- Jelena Zaitseva
- Institute of Biochemistry, Biocenter, Johann-Wolfgang Goethe University Frankfurt, Frankfurt, Germany
| | - Stefan Jenewein
- Institute of Biochemistry, Biocenter, Johann-Wolfgang Goethe University Frankfurt, Frankfurt, Germany
| | - Thorsten Jumpertz
- Institute of Biochemistry, Biocenter, Johann-Wolfgang Goethe University Frankfurt, Frankfurt, Germany
| | - I Barry Holland
- Institut de Génétique et Microbiologie, Bât. 409, Université de Paris XI, Orsay, France
| | - Lutz Schmitt
- Institute of Biochemistry, Biocenter, Johann-Wolfgang Goethe University Frankfurt, Frankfurt, Germany
- Institute of Biochemistry, Biocenter, Johann-Wolfgang Goethe University Frankfurt, Marie Curie Strasse 9, 60439 Frankfurt, Germany. Tel.: +49 69 79829 569; Fax: +49 69 79829 495; E-mail:
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