1
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Ober VT, Githure GB, Volpato Santos Y, Becker S, Moya Munoz G, Basquin J, Schwede F, Lorentzen E, Boshart M. Purine nucleosides replace cAMP in allosteric regulation of PKA in trypanosomatid pathogens. eLife 2024; 12:RP91040. [PMID: 38517938 PMCID: PMC10959531 DOI: 10.7554/elife.91040] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/24/2024] Open
Abstract
Cyclic nucleotide binding domains (CNB) confer allosteric regulation by cAMP or cGMP to many signaling proteins, including PKA and PKG. PKA of phylogenetically distant Trypanosoma is the first exception as it is cyclic nucleotide-independent and responsive to nucleoside analogues (Bachmaier et al., 2019). Here, we show that natural nucleosides inosine, guanosine and adenosine are nanomolar affinity CNB ligands and activators of PKA orthologs of the important tropical pathogens Trypanosoma brucei, Trypanosoma cruzi, and Leishmania. The sequence and structural determinants of binding affinity, -specificity and kinase activation of PKAR were established by structure-activity relationship (SAR) analysis, co-crystal structures and mutagenesis. Substitution of two to three amino acids in the binding sites is sufficient for conversion of CNB domains from nucleoside to cyclic nucleotide specificity. In addition, a trypanosomatid-specific C-terminal helix (αD) is required for high affinity binding to CNB-B. The αD helix functions as a lid of the binding site that shields ligands from solvent. Selectivity of guanosine for CNB-B and of adenosine for CNB-A results in synergistic kinase activation at low nanomolar concentration. PKA pulldown from rapid lysis establishes guanosine as the predominant ligand in vivo in T. brucei bloodstream forms, whereas guanosine and adenosine seem to synergize in the procyclic developmental stage in the insect vector. We discuss the versatile use of CNB domains in evolution and recruitment of PKA for novel nucleoside-mediated signaling.
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Affiliation(s)
- Veronica Teresa Ober
- Faculty of Biology, Genetics, Ludwig-Maximilians University Munich (LMU)MartinsriedGermany
| | | | - Yuri Volpato Santos
- Faculty of Biology, Genetics, Ludwig-Maximilians University Munich (LMU)MartinsriedGermany
| | - Sidney Becker
- Max Planck Institute of Molecular PhysiologyDortmundGermany
- TU Dortmund, Department of Chemistry and Chemical BiologyDortmundGermany
| | - Gabriel Moya Munoz
- Faculty of Biology, Genetics, Ludwig-Maximilians University Munich (LMU)MartinsriedGermany
| | | | - Frank Schwede
- BIOLOG Life Science Institute GmbH & Co KGBremenGermany
| | - Esben Lorentzen
- Department of Molecular Biology and Genetics, Aarhus UniversityAarhusDenmark
| | - Michael Boshart
- Faculty of Biology, Genetics, Ludwig-Maximilians University Munich (LMU)MartinsriedGermany
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2
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Sharma R, Kim JJ, Qin L, Henning P, Akimoto M, VanSchouwen B, Kaur G, Sankaran B, MacKenzie KR, Melacini G, Casteel DE, Herberg FW, Kim CW. An auto-inhibited state of protein kinase G and implications for selective activation. eLife 2022; 11:79530. [PMID: 35929723 PMCID: PMC9417419 DOI: 10.7554/elife.79530] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2022] [Accepted: 08/04/2022] [Indexed: 11/29/2022] Open
Abstract
Cyclic GMP-dependent protein kinases (PKGs) are key mediators of the nitric oxide/cyclic guanosine monophosphate (cGMP) signaling pathway that regulates biological functions as diverse as smooth muscle contraction, cardiac function, and axon guidance. Understanding how cGMP differentially triggers mammalian PKG isoforms could lead to new therapeutics that inhibit or activate PKGs, complementing drugs that target nitric oxide synthases and cyclic nucleotide phosphodiesterases in this signaling axis. Alternate splicing of PRKG1 transcripts confers distinct leucine zippers, linkers, and auto-inhibitory (AI) pseudo-substrate sequences to PKG Iα and Iβ that result in isoform-specific activation properties, but the mechanism of enzyme auto-inhibition and its alleviation by cGMP is not well understood. Here, we present a crystal structure of PKG Iβ in which the AI sequence and the cyclic nucleotide-binding (CNB) domains are bound to the catalytic domain, providing a snapshot of the auto-inhibited state. Specific contacts between the PKG Iβ AI sequence and the enzyme active site help explain isoform-specific activation constants and the effects of phosphorylation in the linker. We also present a crystal structure of a PKG I CNB domain with an activating mutation linked to Thoracic Aortic Aneurysms and Dissections. Similarity of this structure to wildtype cGMP-bound domains and differences with the auto-inhibited enzyme provide a mechanistic basis for constitutive activation. We show that PKG Iβ auto-inhibition is mediated by contacts within each monomer of the native full-length dimeric protein, and using the available structural and biochemical data we develop a model for the regulation and cooperative activation of PKGs.
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Affiliation(s)
- Rajesh Sharma
- Department of Pharmacology and Chemical Biology, Baylor College of Medicine, Houston, United States
| | - Jeong Joo Kim
- Department of Pharmacology and Chemical Biology, Baylor College of Medicine, Houston, United States
| | - Liying Qin
- Department of Pharmacology and Chemical Biology, Baylor College of Medicine, Houston, United States
| | - Philipp Henning
- Department of Biochemistry, University of Kassel, kassel, Germany
| | - Madoka Akimoto
- Department of Chemistry and Chemical Biology, McMaster University, Ontario, Canada
| | - Bryan VanSchouwen
- Department of Chemistry and Chemical Biology, McMaster University, Ontario, Canada
| | - Gundeep Kaur
- Department of Pharmacology and Chemical Biology, Baylor College of Medicine, Houston, United States
| | - Banumathi Sankaran
- Berkeley Center for Structural Biology, Lawrence Berkeley National Laboratory, Berkeley, United States
| | - Kevin R MacKenzie
- Department of Pharmacology and Chemical Biology, Baylor College of Medicine, Houston, United States
| | - Giuseppe Melacini
- Department of Chemistry and Chemical Biology, McMaster University, Hamilton, Canada
| | - Darren E Casteel
- Department of Medicine, University of California, San Diego, San Diego, United States
| | - Fritz W Herberg
- Department of Biochemistry, University of Kassel, kassel, Germany
| | - Choel W Kim
- Department of Pharmacology and Chemical Biology, Baylor College of Medicine, Houston, United States
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3
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Byun JA, VanSchouwen B, Huang J, Baryar U, Melacini G. Divergent allostery reveals critical differences between structurally homologous regulatory domains of Plasmodium falciparum and human protein kinase G. J Biol Chem 2022; 298:101691. [PMID: 35143840 PMCID: PMC8931422 DOI: 10.1016/j.jbc.2022.101691] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2021] [Revised: 02/01/2022] [Accepted: 02/02/2022] [Indexed: 11/24/2022] Open
Abstract
Malaria is a life-threatening infectious disease primarily caused by the Plasmodium falciparum parasite. The increasing resistance to current antimalarial drugs and their side effects has led to an urgent need for novel malaria drug targets, such as the P. falciparum cGMP-dependent protein kinase (pfPKG). However, PKG plays an essential regulatory role also in the human host. Human PKG (hPKG) and pfPKG are controlled by structurally homologs cGMP-binding domains (CBDs). Here, we show that despite the structural similarities between the essential CBDs in pfPKG and hPKG, their respective allosteric networks differ significantly. Through comparative analyses of CHESCA, molecular dynamics simulations, and backbone internal dynamics measurements, we found that conserved allosteric elements within the essential CBDs are wired differently in pfPKG and hPKG to implement cGMP-dependent kinase activation. Such pfPKG vs. hPKG rewiring of allosteric networks was unexpected due to the structural similarity between the two essential CBDs. Yet, such finding provides crucial information on which elements to target for selective inhibition of pfPKG vs. hPKG, which may potentially reduce undesired side-effects in malaria treatments.
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Affiliation(s)
- Jung Ah Byun
- Department of Biochemistry and Biomedical Sciences, McMaster University, 1280 Main St. W. Hamilton, Canada
| | - Bryan VanSchouwen
- Department of Chemistry and Chemical Biology, McMaster University, 1280 Main St. W. Hamilton, Canada
| | - Jinfeng Huang
- Department of Chemistry and Chemical Biology, McMaster University, 1280 Main St. W. Hamilton, Canada
| | - Ubaidullah Baryar
- Department of Chemistry and Chemical Biology, McMaster University, 1280 Main St. W. Hamilton, Canada
| | - Giuseppe Melacini
- Department of Biochemistry and Biomedical Sciences, McMaster University, 1280 Main St. W. Hamilton, Canada; Department of Chemistry and Chemical Biology, McMaster University, 1280 Main St. W. Hamilton, Canada.
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4
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Neutron crystallography reveals mechanisms used by Pseudomonas aeruginosa for host-cell binding. Nat Commun 2022; 13:194. [PMID: 35017516 PMCID: PMC8752737 DOI: 10.1038/s41467-021-27871-8] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2021] [Accepted: 12/15/2021] [Indexed: 12/22/2022] Open
Abstract
The opportunistic pathogen Pseudomonas aeruginosa, a major cause of nosocomial infections, uses carbohydrate-binding proteins (lectins) as part of its binding to host cells. The fucose-binding lectin, LecB, displays a unique carbohydrate-binding site that incorporates two closely located calcium ions bridging between the ligand and protein, providing specificity and unusually high affinity. Here, we investigate the mechanisms involved in binding based on neutron crystallography studies of a fully deuterated LecB/fucose/calcium complex. The neutron structure, which includes the positions of all the hydrogen atoms, reveals that the high affinity of binding may be related to the occurrence of a low-barrier hydrogen bond induced by the proximity of the two calcium ions, the presence of coordination rings between the sugar, calcium and LecB, and the dynamic behaviour of bridging water molecules at room temperature. These key structural details may assist in the design of anti-adhesive compounds to combat multi-resistance bacterial infections. Pseudomonas aeruginosa employs lectins to bind to its host cells, and is known to be the major cause of lung infections. Lectin B (LecB) from Pseudomonas aeruginosa binds specifically to galactose and fucose and is important for pathogenicity, adhesion and biofilm formation. In this work, the neutron crystal structure (1.9 Å) of the deuterated LecB/Ca/fucose complex is reported. The structure, in combination with perdeuteration of the ligand and the receptor allowed the observation of hydrogen atoms, protonation states and hydrogen bonds involved in the interaction between pathogenic bacteria and host cells. Thus the study provides structural insights into the mechanism of high affinity binding of LecB to its targets.
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5
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Mutual Protein-Ligand Conformational Selection Drives cGMP vs. cAMP Selectivity in Protein Kinase G. J Mol Biol 2021; 433:167202. [PMID: 34400180 DOI: 10.1016/j.jmb.2021.167202] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2021] [Revised: 07/21/2021] [Accepted: 08/09/2021] [Indexed: 11/24/2022]
Abstract
Protein kinase G (PKG) is a major receptor of cGMP, and controls signaling pathways distinct from those regulated by cAMP. However, the contributions of the two substituents that differentiate cGMP from cAMP (i.e. 6-oxo and 2-NH2) to the cGMP-versus-cAMP selectivity of PKG remain unclear. Here, using NMR to map how binding affinity and dynamics of the protein and ligand vary along a ligand double-substitution cycle, we show that the contributions of the two substituents to binding affinity are surprisingly non-additive. Such non-additivity stems primarily from mutual protein-ligand conformational selection, whereby not only does the ligand select for a preferred protein conformation upon binding, but also, the protein selects for a preferred ligand conformation. The 6-oxo substituent mainly controls the conformational equilibrium of the bound protein, while the 2-NH2 substituent primarily controls the conformational equilibrium of the unbound ligand (i.e. syn versus anti). Therefore, understanding the conformational dynamics of both the protein and ligand is essential to explain the cGMP-versus-cAMP selectivity of PKG.
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6
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Abstract
X-ray crystallography enables detailed structural studies of proteins to understand and modulate their function. Conducting crystallographic experiments at cryogenic temperatures has practical benefits but potentially limits the identification of functionally important alternative protein conformations that can be revealed only at room temperature (RT). This review discusses practical aspects of preparing, acquiring, and analyzing X-ray crystallography data at RT to demystify preconceived impracticalities that freeze progress of routine RT data collection at synchrotron sources. Examples are presented as conceptual and experimental templates to enable the design of RT-inspired studies; they illustrate the diversity and utility of gaining novel insights into protein conformational landscapes. An integrative view of protein conformational dynamics enables opportunities to advance basic and biomedical research.
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7
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Byun JA, VanSchouwen B, Akimoto M, Melacini G. Allosteric inhibition explained through conformational ensembles sampling distinct "mixed" states. Comput Struct Biotechnol J 2020; 18:3803-3818. [PMID: 33335680 PMCID: PMC7720024 DOI: 10.1016/j.csbj.2020.10.026] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2020] [Revised: 10/24/2020] [Accepted: 10/25/2020] [Indexed: 11/29/2022] Open
Abstract
Allosteric modulation provides an effective avenue for selective and potent enzyme inhibition. Here, we summarize and critically discuss recent advances on the mechanisms of allosteric partial agonists for three representative signalling enzymes activated by cyclic nucleotides: the cAMP-dependent protein kinase (PKA), the cGMP-dependent protein kinase (PKG), and the exchange protein activated by cAMP (EPAC). The comparative analysis of partial agonism in PKA, PKG and EPAC reveals a common emerging theme, i.e. the sampling of distinct “mixed” conformational states, either within a single domain or between distinct domains. Here, we show how such “mixed” states play a crucial role in explaining the observed functional response, i.e. partial agonism and allosteric pluripotency, as well as in maximizing inhibition while minimizing potency losses. In addition, by combining Nuclear Magnetic Resonance (NMR), Molecular Dynamics (MD) simulations and Ensemble Allosteric Modeling (EAM), we also show how to map the free-energy landscape of conformational ensembles containing “mixed” states. By discussing selected case studies, we illustrate how MD simulations and EAM complement NMR to quantitatively relate protein dynamics to function. The resulting NMR- and MD-based EAMs are anticipated to inform not only the design of new generations of highly selective allosteric inhibitors, but also the choice of multidrug combinations.
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Affiliation(s)
- Jung Ah Byun
- Department of Biochemistry and Biomedical Sciences, McMaster University, Hamilton, Ontario, Canada
| | - Bryan VanSchouwen
- Department of Chemistry and Chemical Biology, McMaster University, Hamilton, Ontario, Canada
| | - Madoka Akimoto
- Department of Chemistry and Chemical Biology, McMaster University, Hamilton, Ontario, Canada
| | - Giuseppe Melacini
- Department of Biochemistry and Biomedical Sciences, McMaster University, Hamilton, Ontario, Canada.,Department of Chemistry and Chemical Biology, McMaster University, Hamilton, Ontario, Canada
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8
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Structures of the cGMP-dependent protein kinase in malaria parasites reveal a unique structural relay mechanism for activation. Proc Natl Acad Sci U S A 2019; 116:14164-14173. [PMID: 31239348 PMCID: PMC6628679 DOI: 10.1073/pnas.1905558116] [Citation(s) in RCA: 26] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The cyclic guanosine-3',5'-monophosphate (cGMP)-dependent protein kinase (PKG) was identified >25 y ago; however, efforts to obtain a structure of the entire PKG enzyme or catalytic domain from any species have failed. In malaria parasites, cooperative activation of PKG triggers crucial developmental transitions throughout the complex life cycle. We have determined the cGMP-free crystallographic structures of PKG from Plasmodium falciparum and Plasmodium vivax, revealing how key structural components, including an N-terminal autoinhibitory segment (AIS), four predicted cyclic nucleotide-binding domains (CNBs), and a kinase domain (KD), are arranged when the enzyme is inactive. The four CNBs and the KD are in a pentagonal configuration, with the AIS docked in the substrate site of the KD in a swapped-domain dimeric arrangement. We show that although the protein is predominantly a monomer (the dimer is unlikely to be representative of the physiological form), the binding of the AIS is necessary to keep Plasmodium PKG inactive. A major feature is a helix serving the dual role of the N-terminal helix of the KD as well as the capping helix of the neighboring CNB. A network of connecting helices between neighboring CNBs contributes to maintaining the kinase in its inactive conformation. We propose a scheme in which cooperative binding of cGMP, beginning at the CNB closest to the KD, transmits conformational changes around the pentagonal molecule in a structural relay mechanism, enabling PKG to orchestrate rapid, highly regulated developmental switches in response to dynamic modulation of cGMP levels in the parasite.
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9
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Gerlits O, Kong X, Cheng X, Wymore T, Blumenthal DK, Taylor P, Radić Z, Kovalevsky A. Productive reorientation of a bound oxime reactivator revealed in room temperature X-ray structures of native and VX-inhibited human acetylcholinesterase. J Biol Chem 2019; 294:10607-10618. [PMID: 31138650 DOI: 10.1074/jbc.ra119.008725] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2019] [Revised: 05/21/2019] [Indexed: 11/06/2022] Open
Abstract
Exposure to organophosphorus compounds (OPs) may be fatal if untreated, and a clear and present danger posed by nerve agent OPs has become palpable in recent years. OPs inactivate acetylcholinesterase (AChE) by covalently modifying its catalytic serine. Inhibited AChE cannot hydrolyze the neurotransmitter acetylcholine leading to its build-up at the cholinergic synapses and creating an acute cholinergic crisis. Current antidotes, including oxime reactivators that attack the OP-AChE conjugate to free the active enzyme, are inefficient. Better reactivators are sought, but their design is hampered by a conformationally rigid portrait of AChE extracted exclusively from 100K X-ray crystallography and scarcity of structural knowledge on human AChE (hAChE). Here, we present room temperature X-ray structures of native and VX-phosphonylated hAChE with an imidazole-based oxime reactivator, RS-170B. We discovered that inhibition with VX triggers substantial conformational changes in bound RS-170B from a "nonproductive" pose (the reactive aldoxime group points away from the VX-bound serine) in the reactivator-only complex to a "semi-productive" orientation in the VX-modified complex. This observation, supported by concurrent molecular simulations, suggested that the narrow active-site gorge of hAChE may be significantly more dynamic than previously thought, allowing RS-170B to reorient inside the gorge. Furthermore, we found that small molecules can bind in the choline-binding site hindering approach to the phosphorous of VX-bound serine. Our results provide structural and mechanistic perspectives on the reactivation of OP-inhibited hAChE and demonstrate that structural studies at physiologically relevant temperatures can deliver previously overlooked insights applicable for designing next-generation antidotes.
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Affiliation(s)
- Oksana Gerlits
- From the Bredesen Center, University of Tennessee, Knoxville, Tennessee 37996
| | - Xiaotian Kong
- the Division of Medicinal Chemistry and Pharmacognosy, College of Pharmacy, The Ohio State University, Columbus, Ohio 43210
| | - Xiaolin Cheng
- the Division of Medicinal Chemistry and Pharmacognosy, College of Pharmacy, The Ohio State University, Columbus, Ohio 43210
| | - Troy Wymore
- the Department of Chemistry, University of Michigan, Ann Arbor, Michigan 48109
| | - Donald K Blumenthal
- the Department of Pharmacology and Toxicology, University of Utah, Salt Lake City, Utah 84112
| | - Palmer Taylor
- the Skaggs School of Pharmacy and Pharmaceutical Sciences, University of California San Diego, La Jolla, California 92093-0751, and
| | - Zoran Radić
- the Skaggs School of Pharmacy and Pharmaceutical Sciences, University of California San Diego, La Jolla, California 92093-0751, and
| | - Andrey Kovalevsky
- the Neutron Scattering Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831
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10
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Gerlits O, Campbell JC, Blakeley MP, Kim C, Kovalevsky A. Neutron Crystallography Detects Differences in Protein Dynamics: Structure of the PKG II Cyclic Nucleotide Binding Domain in Complex with an Activator. Biochemistry 2018. [PMID: 29517905 DOI: 10.1021/acs.biochem.8b00010] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
As one of the main receptors of a second messenger, cGMP, cGMP-dependent protein kinase (PKG) isoforms I and II regulate distinct physiological processes. The design of isoform-specific activators is thus of great biomedical importance and requires detailed structural information about PKG isoforms bound with activators, including accurate positions of hydrogen atoms and a description of the hydrogen bonding and water architecture. Here, we determined a 2.2 Å room-temperature joint X-ray/neutron (XN) structure of the human PKG II carboxyl cyclic nucleotide binding (CNB-B) domain bound with a potent PKG II activator, 8-pCPT-cGMP. The XN structure directly visualizes intermolecular interactions and reveals changes in hydrogen bonding patterns upon comparison to the X-ray structure determined at cryo-temperatures. Comparative analysis of the backbone hydrogen/deuterium exchange patterns in PKG II:8-pCPT-cGMP and previously reported PKG Iβ:cGMP XN structures suggests that the ability of these agonists to activate PKG is related to how effectively they quench dynamics of the cyclic nucleotide binding pocket and the surrounding regions.
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Affiliation(s)
- Oksana Gerlits
- Bredesen Center , University of Tennessee , Knoxville , Tennessee 37996 , United States
| | - James C Campbell
- Department of Pharmacology and Chemical Biology , Baylor College of Medicine , Houston , Texas 77030 , United States
| | - Matthew P Blakeley
- Large-Scale Structures Group , Institut Laue Langevin , 38042 Grenoble Cedex 9, France
| | - Choel Kim
- Department of Pharmacology and Chemical Biology , Baylor College of Medicine , Houston , Texas 77030 , United States.,Verna and Marrs McLean Department of Biochemistry and Molecular Biology , Baylor College of Medicine , Houston , Texas 77030 , United States
| | - Andrey Kovalevsky
- Neutron Scattering Division, Neutron Sciences Directorate , Oak Ridge National Laboratory , Oak Ridge , Tennessee 37831 , United States
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11
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Neutron macromolecular crystallography. Emerg Top Life Sci 2018; 2:39-55. [DOI: 10.1042/etls20170083] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2017] [Revised: 12/12/2017] [Accepted: 12/19/2017] [Indexed: 01/02/2023]
Abstract
Neutron diffraction techniques permit direct determination of the hydrogen (H) and deuterium (D) positions in crystal structures of biological macromolecules at resolutions of ∼1.5 and 2.5 Å, respectively. In addition, neutron diffraction data can be collected from a single crystal at room temperature without radiation damage issues. By locating the positions of H/D-atoms, protonation states and water molecule orientations can be determined, leading to a more complete understanding of many biological processes and drug-binding. In the last ca. 5 years, new beamlines have come online at reactor neutron sources, such as BIODIFF at Heinz Maier-Leibnitz Zentrum and IMAGINE at Oak Ridge National Laboratory (ORNL), and at spallation neutron sources, such as MaNDi at ORNL and iBIX at the Japan Proton Accelerator Research Complex. In addition, significant improvements have been made to existing beamlines, such as LADI-III at the Institut Laue-Langevin. The new and improved instrumentations are allowing sub-mm3 crystals to be regularly used for data collection and permitting the study of larger systems (unit-cell edges >100 Å). Owing to this increase in capacity and capability, many more studies have been performed and for a wider range of macromolecules, including enzymes, signalling proteins, transport proteins, sugar-binding proteins, fluorescent proteins, hormones and oligonucleotides; of the 126 structures deposited in the Protein Data Bank, more than half have been released since 2013 (65/126, 52%). Although the overall number is still relatively small, there are a growing number of examples for which neutron macromolecular crystallography has provided the answers to questions that otherwise remained elusive.
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12
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Lorenz R, Bertinetti D, Herberg FW. cAMP-Dependent Protein Kinase and cGMP-Dependent Protein Kinase as Cyclic Nucleotide Effectors. Handb Exp Pharmacol 2017; 238:105-122. [PMID: 27885524 DOI: 10.1007/164_2015_36] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
The cAMP-dependent protein kinase (PKA) and the cGMP-dependent protein kinase (PKG) are homologous enzymes with different binding and activation specificities for cyclic nucleotides. Both enzymes harbor conserved cyclic nucleotide-binding (CNB) domains. Differences in amino acid composition of these CNB domains mediate cyclic nucleotide selectivity in PKA and PKG, respectively. Recently, the presence of the noncanonical cyclic nucleotides cCMP and cUMP in eukaryotic cells has been proven, while the existence of cellular cIMP and cXMP remains unclear. It was shown that the main effectors of cyclic nucleotide signaling, PKA and PKG, can be activated by each of these noncanonical cyclic nucleotides. With unique effector proteins still missing, such cross-activation effects might have physiological relevance. Therefore, we approach PKA and PKG as cyclic nucleotide effectors in this chapter. The focus of this chapter is the general cyclic nucleotide-binding properties of both kinases as well as the selectivity for cAMP or cGMP, respectively. Furthermore, we discuss the binding affinities and activation potencies of noncanonical cyclic nucleotides.
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Affiliation(s)
- Robin Lorenz
- Department of Biochemistry, University of Kassel, Heinrich-Plett-Str. 40, 34132, Kassel, Germany
| | - Daniela Bertinetti
- Department of Biochemistry, University of Kassel, Heinrich-Plett-Str. 40, 34132, Kassel, Germany
| | - Friedrich W Herberg
- Department of Biochemistry, University of Kassel, Heinrich-Plett-Str. 40, 34132, Kassel, Germany.
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13
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Yokoyama T, Ostermann A, Schrader TE, Mizuguchi M. Large-scale crystallization and neutron crystallographic analysis of HSP70 in complex with ADP. Acta Crystallogr F Struct Biol Commun 2017; 73:555-559. [PMID: 28994403 PMCID: PMC5633922 DOI: 10.1107/s2053230x1701264x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2017] [Accepted: 09/03/2017] [Indexed: 11/10/2022] Open
Abstract
HSP70 belongs to the heat-shock protein family and binds to unfolded proteins, driven by ATP hydrolysis, in order to prevent aggregation. Previous X-ray crystallographic analyses of HSP70 have shown that HSP70 binds to ADP with internal water molecules. In order to elucidate the role of the water molecules, including their H/D atoms, a neutron diffraction study of the human HSP70 ATPase domain was initiated. Deuterated large crystals of the HSP-ADP complex (1.2-1.8 mm3) were successfully grown by large-scale crystallization, and a neutron diffraction experiment at BIODIFF resulted in diffraction to a maximum resolution of 2.2 Å. After data reduction, the overall completeness, Rmeas and average I/σ(I) were 90.4%, 11.7% and 8.1, respectively, indicating that the data set was sufficient to visualize H and D atoms.
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Affiliation(s)
- Takeshi Yokoyama
- Faculty of Pharmaceutical Sciences, University of Toyama, 2630 Sugutani, Toyama 930-0914, Japan
| | - Andreas Ostermann
- Heinz Maier-Leibnitz Zentrum (MLZ), Technische Universtät München, Lichtenbergstrasse 1, 85748 Garching, Germany
| | - Tobias E. Schrader
- Jülich Centre for Neutron Science (JCNS) at Heinz Maier-Leibnitz Zentrum (MLZ), Forschungszentrum Jülich GmbH, Lichtenbergstrasse 1, 85748 Garching, Germany
| | - Mineyuki Mizuguchi
- Faculty of Pharmaceutical Sciences, University of Toyama, 2630 Sugutani, Toyama 930-0914, Japan
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14
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VanSchouwen B, Ahmed R, Milojevic J, Melacini G. Functional dynamics in cyclic nucleotide signaling and amyloid inhibition. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2017; 1865:1529-1543. [PMID: 28911813 DOI: 10.1016/j.bbapap.2017.09.005] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Received: 07/06/2017] [Revised: 08/29/2017] [Accepted: 09/07/2017] [Indexed: 12/28/2022]
Abstract
It is now established that understanding the molecular basis of biological function requires atomic resolution maps of both structure and dynamics. Here, we review several illustrative examples of functional dynamics selected from our work on cyclic nucleotide signaling and amyloid inhibition. Although fundamentally diverse, a central aspect common to both fields is that function can only be rationalized by considering dynamic equilibria between distinct states of the accessible free energy landscape. The dynamic exchange between ground and excited states of signaling proteins is essential to explain auto-inhibition and allosteric activation. The dynamic exchange between non-toxic monomeric species and toxic oligomers of amyloidogenic proteins provides a foundation to understand amyloid inhibition. NMR ideally probes both types of dynamic exchange at atomic resolution. Specifically, we will show how NMR was utilized to reveal the dynamical basis of cyclic nucleotide affinity, selectivity, agonism and antagonism in multiple eukaryotic cAMP and cGMP receptors. We will also illustrate how NMR revealed the mechanism of action of plasma proteins that act as extracellular chaperones and inhibit the self-association of the prototypical amyloidogenic Aβ peptide. The examples outlined in this review illustrate the widespread implications of functional dynamics and the power of NMR as an indispensable tool in molecular pharmacology and pathology.
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Affiliation(s)
- Bryan VanSchouwen
- Department of Chemistry and Chemical Biology, McMaster University, Hamilton, Ontario, Canada
| | - Rashik Ahmed
- Department of Biochemistry and Biomedical Sciences, McMaster University, Hamilton, Ontario, Canada
| | - Julijana Milojevic
- Department of Chemistry and Chemical Biology, McMaster University, Hamilton, Ontario, Canada
| | - Giuseppe Melacini
- Department of Chemistry and Chemical Biology, McMaster University, Hamilton, Ontario, Canada; Department of Biochemistry and Biomedical Sciences, McMaster University, Hamilton, Ontario, Canada.
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15
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Mutations of PKA cyclic nucleotide-binding domains reveal novel aspects of cyclic nucleotide selectivity. Biochem J 2017; 474:2389-2403. [PMID: 28583991 DOI: 10.1042/bcj20160969] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2016] [Revised: 06/02/2017] [Accepted: 06/05/2017] [Indexed: 11/17/2022]
Abstract
Cyclic AMP and cyclic GMP are ubiquitous second messengers that regulate the activity of effector proteins in all forms of life. The main effector proteins, the 3',5'-cyclic adenosine monophosphate (cAMP)-dependent protein kinase (PKA) and the 3',5'-cyclic guanosine monophosphate (cGMP)-dependent protein kinase (PKG), are preferentially activated by cAMP and cGMP, respectively. However, the molecular basis of this cyclic nucleotide selectivity is still not fully understood. Analysis of isolated cyclic nucleotide-binding (CNB) domains of PKA regulatory subunit type Iα (RIα) reveals that the C-terminal CNB-B has a higher cAMP affinity and selectivity than the N-terminal CNB-A. Here, we show that introducing cGMP-specific residues using site-directed mutagenesis reduces the selectivity of CNB-B, while the combination of two mutations (G316R/A336T) results in a cGMP-selective binding domain. Furthermore, introducing the corresponding mutations (T192R/A212T) into the PKA RIα CNB-A turns this domain into a highly cGMP-selective domain, underlining the importance of these contacts for achieving cGMP specificity. Binding data with the generic purine nucleotide 3',5'-cyclic inosine monophosphate (cIMP) reveal that introduced arginine residues interact with the position 6 oxygen of the nucleobase. Co-crystal structures of an isolated CNB-B G316R/A336T double mutant with either cAMP or cGMP reveal that the introduced threonine and arginine residues maintain their conserved contacts as seen in PKG I CNB-B. These results improve our understanding of cyclic nucleotide binding and the molecular basis of cyclic nucleotide specificity.
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16
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Campbell JC, VanSchouwen B, Lorenz R, Sankaran B, Herberg FW, Melacini G, Kim C. Crystal structure of cGMP-dependent protein kinase Iβ cyclic nucleotide-binding-B domain : Rp-cGMPS complex reveals an apo-like, inactive conformation. FEBS Lett 2016; 591:221-230. [PMID: 27914169 DOI: 10.1002/1873-3468.12505] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2016] [Revised: 10/13/2016] [Accepted: 11/18/2016] [Indexed: 12/23/2022]
Abstract
The R-diastereomer of phosphorothioate analogs of cGMP, Rp-cGMPS, is one of few known inhibitors of cGMP-dependent protein kinase I (PKG I); however, its mechanism of inhibition is currently not fully understood. Here, we determined the crystal structure of the PKG Iβ cyclic nucleotide-binding domain (PKG Iβ CNB-B), considered a 'gatekeeper' for cGMP activation, bound to Rp-cGMPS at 1.3 Å. Our structural and NMR data show that PKG Iβ CNB-B bound to Rp-cGMPS displays an apo-like structure with its helical domain in an open conformation. Comparison with the cAMP-dependent protein kinase regulatory subunit (PKA RIα) showed that this conformation resembles the catalytic subunit-bound inhibited state of PKA RIα more closely than the apo or Rp-cAMPS-bound conformations. These results suggest that Rp-cGMPS inhibits PKG I by stabilizing the inactive conformation of CNB-B.
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Affiliation(s)
- James C Campbell
- Structural and Computational Biology and Molecular Biophysics Program, Baylor College of Medicine, Houston, TX, USA.,Department of Pharmacology, Baylor College of Medicine, Houston, TX, USA
| | - Bryan VanSchouwen
- Department of Chemistry and Chemical Biology, McMaster University, Hamilton, Canada
| | - Robin Lorenz
- Department of Biochemistry, University of Kassel, Kassel, Hesse, Germany
| | - Banumathi Sankaran
- Berkeley Center for Structural Biology, Lawrence Berkeley National Laboratory, CA, USA
| | | | - Giuseppe Melacini
- Department of Chemistry and Chemical Biology, McMaster University, Hamilton, Canada
| | - Choel Kim
- Structural and Computational Biology and Molecular Biophysics Program, Baylor College of Medicine, Houston, TX, USA.,Department of Pharmacology, Baylor College of Medicine, Houston, TX, USA.,Verna and Marrs McLean Department of Biochemistry and Molecular Biology, Baylor College of Medicine, Houston, TX, USA
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17
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Abstract
Since drugs bind to their targets through directional H bonding and non-directional hydrophobic and electrostatic interactions, neutron crystallography can help guide structure-based drug design. This is illustrated by McKenna and co-workers [Aggarwal et al. (2016), IUCrJ, 3, 319-325] who describe the room-temperature neutron structure of human carbonic anyhydrase II in complex with the clinical inhibitor methazolamide to 2.2 Å resolution, and compare this with the previously determined room-temperature neutron structure of human carbonic anyhydrase II in complex with the clinical inhibitor acetazolamide to 2.0 Å resolution [Fisher et al. (2012). J. Am. Chem. Soc.134, 14726-14729].
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Affiliation(s)
- M. P. Blakeley
- Large-Scale Structures Group, Institut Laue-Langevin, 71 Avenue des Martyrs, Grenoble, 38000, France
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18
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The use of neutron scattering to determine the functional structure of glycoside hydrolase. Curr Opin Struct Biol 2016; 40:54-61. [PMID: 27494120 DOI: 10.1016/j.sbi.2016.07.014] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2016] [Revised: 07/19/2016] [Accepted: 07/21/2016] [Indexed: 11/21/2022]
Abstract
Neutron diffraction provides different information from X-ray diffraction, because neutrons are scattered by atomic nuclei, whereas X-rays are scattered by electrons. One of the key advantages of neutron crystallography is the ability to visualize hydrogen and deuterium atoms, making it possible to observe the protonation state of amino acid residues, hydrogen bonds, networks of water molecules and proton relay pathways in enzymes. But, because of technical difficulties, less than 100 enzyme structures have been evaluated by neutron crystallography to date. In this review, we discuss the advantages and disadvantages of neutron crystallography as a tool to investigate the functional structure of glycoside hydrolases, with some examples.
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19
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Kim JJ, Lorenz R, Arold ST, Reger AS, Sankaran B, Casteel DE, Herberg FW, Kim C. Crystal Structure of PKG I:cGMP Complex Reveals a cGMP-Mediated Dimeric Interface that Facilitates cGMP-Induced Activation. Structure 2016; 24:710-720. [PMID: 27066748 DOI: 10.1016/j.str.2016.03.009] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2015] [Revised: 01/21/2016] [Accepted: 03/04/2016] [Indexed: 10/22/2022]
Abstract
Cyclic guanosine monophosphate (cGMP)-dependent protein kinase (PKG) is a key regulator of smooth muscle and vascular tone and represents an important drug target for treating hypertensive diseases and erectile dysfunction. Despite its importance, its activation mechanism is not fully understood. To understand the activation mechanism, we determined a 2.5 Å crystal structure of the PKG I regulatory (R) domain bound with cGMP, which represents the activated state. Although we used a monomeric domain for crystallization, the structure reveals that two R domains form a symmetric dimer where the cGMP bound at high-affinity pockets provide critical dimeric contacts. Small-angle X-ray scattering and mutagenesis support this dimer model, suggesting that the dimer interface modulates kinase activation. Finally, structural comparison with the homologous cyclic AMP-dependent protein kinase reveals that PKG is drastically different from protein kinase A in its active conformation, suggesting a novel activation mechanism for PKG.
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Affiliation(s)
- Jeong Joo Kim
- Department of Pharmacology, Baylor College of Medicine, Houston, TX 77030, USA; Department of Biochemistry, University of Kassel, Kassel, Hesse 34132, Germany
| | - Robin Lorenz
- Department of Biochemistry, University of Kassel, Kassel, Hesse 34132, Germany
| | - Stefan T Arold
- King Abdullah University of Science and Technology (KAUST), Computational Bioscience Research Center, Division of Biological and Environmental Sciences and Engineering, Thuwal 23955-6900, Saudi Arabia
| | - Albert S Reger
- Department of Pharmacology, Baylor College of Medicine, Houston, TX 77030, USA
| | - Banumathi Sankaran
- Berkeley Center for Structural Biology, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA
| | - Darren E Casteel
- Department of Medicine, University of California, San Diego, La Jolla, CA 92093, USA
| | - Friedrich W Herberg
- Department of Biochemistry, University of Kassel, Kassel, Hesse 34132, Germany
| | - Choel Kim
- Department of Pharmacology, Baylor College of Medicine, Houston, TX 77030, USA; Verna and Marrs McLean Department of Biochemistry and Molecular Biology, Baylor College of Medicine, Houston, TX 77030, USA.
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20
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Campbell JC, Kim JJ, Li KY, Huang GY, Reger AS, Matsuda S, Sankaran B, Link TM, Yuasa K, Ladbury JE, Casteel DE, Kim C. Structural Basis of Cyclic Nucleotide Selectivity in cGMP-dependent Protein Kinase II. J Biol Chem 2016; 291:5623-5633. [PMID: 26769964 PMCID: PMC4786703 DOI: 10.1074/jbc.m115.691303] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2015] [Revised: 01/13/2016] [Indexed: 02/04/2023] Open
Abstract
Membrane-bound cGMP-dependent protein kinase (PKG) II is a key regulator of bone growth, renin secretion, and memory formation. Despite its crucial physiological roles, little is known about its cyclic nucleotide selectivity mechanism due to a lack of structural information. Here, we find that the C-terminal cyclic nucleotide binding (CNB-B) domain of PKG II binds cGMP with higher affinity and selectivity when compared with its N-terminal CNB (CNB-A) domain. To understand the structural basis of cGMP selectivity, we solved co-crystal structures of the CNB domains with cyclic nucleotides. Our structures combined with mutagenesis demonstrate that the guanine-specific contacts at Asp-412 and Arg-415 of the αC-helix of CNB-B are crucial for cGMP selectivity and activation of PKG II. Structural comparison with the cGMP selective CNB domains of human PKG I and Plasmodium falciparum PKG (PfPKG) shows different contacts with the guanine moiety, revealing a unique cGMP selectivity mechanism for PKG II.
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Affiliation(s)
- James C Campbell
- From the Structural and Computational Biology and Molecular Biophysics Program
| | - Jeong Joo Kim
- Department of Pharmacology, and; the Department of Biochemistry, University of Kassel, Kassel, Hesse 34132, Germany
| | - Kevin Y Li
- the Department of Biochemistry & Cell Biology, Rice University, Houston, Texas 77005
| | - Gilbert Y Huang
- Verna and Marrs McLean Department of Biochemistry and Molecular Biology, Baylor College of Medicine, Houston, Texas 77030
| | | | - Shinya Matsuda
- the Department of Biological Science and Technology, the University of Tokushima Graduate School, Tokushima 770-8506, Japan
| | - Banumathi Sankaran
- the Berkeley Center for Structural Biology, Lawrence Berkeley National Laboratory, Berkeley, California 94720
| | - Todd M Link
- the Department of Biochemistry and Molecular Biology, The University of Texas M.D. Anderson Cancer Center, Houston, Texas 77030, and
| | - Keizo Yuasa
- the Department of Biological Science and Technology, the University of Tokushima Graduate School, Tokushima 770-8506, Japan
| | - John E Ladbury
- From the Structural and Computational Biology and Molecular Biophysics Program,; the Department of Biochemistry and Molecular Biology, The University of Texas M.D. Anderson Cancer Center, Houston, Texas 77030, and
| | - Darren E Casteel
- the Department of Medicine, University of California, San Diego, La Jolla, California 92093
| | - Choel Kim
- From the Structural and Computational Biology and Molecular Biophysics Program,; Department of Pharmacology, and; Verna and Marrs McLean Department of Biochemistry and Molecular Biology, Baylor College of Medicine, Houston, Texas 77030,.
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21
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From bedside to bench--meeting report of the 7th International Conference on cGMP "cGMP: generators, effectors and therapeutic implications" in Trier, Germany, from June 19th to 21st 2015. Naunyn Schmiedebergs Arch Pharmacol 2015; 388:1237-46. [PMID: 26486926 DOI: 10.1007/s00210-015-1176-4] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2015] [Accepted: 09/24/2015] [Indexed: 12/27/2022]
Abstract
During the past decade, our knowledge on the physiology, pathophysiology, basic pharmacology, and clinical pharmacology of the second messenger (cGMP) has increased tremendously. It is now well-established that cGMP, generated by soluble and particulate guanylate cyclases, is highly compartmentalized in cells and regulates numerous body functions. New cGMP-regulated physiological functions include meiosis and temperature perception. cGMP is involved in the genesis of numerous pathologies including cardiovascular, pulmonary, endocrine, metabolic, neuropsychiatric, eye, and tumor diseases. Several new clinical uses of stimulators and activators of soluble guanylate cyclase and of phosphodiesterase inhibitors such as heart failure, kidney failure, cognitive disorders, obesity bronchial asthma, and osteoporosis are emerging. The combination of neprilysin inhibitors-enhancing stimulation of the particulate guanylate cyclase pathway by preventing natriuretic peptide degradation-with angiotensin AT1 receptor antagonists constitutes a novel promising strategy for heart failure treatment. The role of oxidative stress in cGMP signaling, application of cGMP sensors, and gene therapy for degenerative eye diseases are emerging topics. It is anticipated that cGMP research will further prosper over the next years and reach out into more and more basic and clinical disciplines.
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22
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VanSchouwen B, Selvaratnam R, Giri R, Lorenz R, Herberg FW, Kim C, Melacini G. Mechanism of cAMP Partial Agonism in Protein Kinase G (PKG). J Biol Chem 2015; 290:28631-41. [PMID: 26370085 DOI: 10.1074/jbc.m115.685305] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2015] [Indexed: 11/06/2022] Open
Abstract
Protein kinase G (PKG) is a major receptor of cGMP and controls signaling pathways often distinct from those regulated by cAMP. Hence, the selective activation of PKG by cGMP versus cAMP is critical. However, the mechanism of cGMP-versus-cAMP selectivity is only limitedly understood. Although the C-terminal cyclic nucleotide-binding domain B of PKG binds cGMP with higher affinity than cAMP, the intracellular concentrations of cAMP are typically higher than those of cGMP, suggesting that the cGMP-versus-cAMP selectivity of PKG is not controlled uniquely through affinities. Here, we show that cAMP is a partial agonist for PKG, and we elucidate the mechanism for cAMP partial agonism through the comparative NMR analysis of the apo, cGMP-, and cAMP-bound forms of the PKG cyclic nucleotide-binding domain B. We show that although cGMP activation is adequately explained by a two-state conformational selection model, the partial agonism of cAMP arises from the sampling of a third, partially autoinhibited state.
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Affiliation(s)
| | | | - Rajanish Giri
- From the Departments of Chemistry and Chemical Biology and
| | - Robin Lorenz
- the Department of Biochemistry, Kassel University, Heinrich Plett Strasse 40, 34132 Kassel, Germany, and
| | - Friedrich W Herberg
- the Department of Biochemistry, Kassel University, Heinrich Plett Strasse 40, 34132 Kassel, Germany, and
| | - Choel Kim
- the Verna and Marrs McLean Department of Biochemistry and Molecular Biology and Department of Pharmacology, Baylor College of Medicine, Houston, Texas 77030
| | - Giuseppe Melacini
- From the Departments of Chemistry and Chemical Biology and Biochemistry and Biomedical Sciences, McMaster University, Hamilton, Ontario L8S 4M1, Canada,
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23
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Blakeley MP, Hasnain SS, Antonyuk SV. Sub-atomic resolution X-ray crystallography and neutron crystallography: promise, challenges and potential. IUCRJ 2015; 2:464-74. [PMID: 26175905 PMCID: PMC4491318 DOI: 10.1107/s2052252515011239] [Citation(s) in RCA: 74] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/06/2015] [Accepted: 06/09/2015] [Indexed: 05/20/2023]
Abstract
The International Year of Crystallography saw the number of macromolecular structures deposited in the Protein Data Bank cross the 100000 mark, with more than 90000 of these provided by X-ray crystallography. The number of X-ray structures determined to sub-atomic resolution (i.e. ≤1 Å) has passed 600 and this is likely to continue to grow rapidly with diffraction-limited synchrotron radiation sources such as MAX-IV (Sweden) and Sirius (Brazil) under construction. A dozen X-ray structures have been deposited to ultra-high resolution (i.e. ≤0.7 Å), for which precise electron density can be exploited to obtain charge density and provide information on the bonding character of catalytic or electron transfer sites. Although the development of neutron macromolecular crystallography over the years has been far less pronounced, and its application much less widespread, the availability of new and improved instrumentation, combined with dedicated deuteration facilities, are beginning to transform the field. Of the 83 macromolecular structures deposited with neutron diffraction data, more than half (49/83, 59%) were released since 2010. Sub-mm(3) crystals are now regularly being used for data collection, structures have been determined to atomic resolution for a few small proteins, and much larger unit-cell systems (cell edges >100 Å) are being successfully studied. While some details relating to H-atom positions are tractable with X-ray crystallography at sub-atomic resolution, the mobility of certain H atoms precludes them from being located. In addition, highly polarized H atoms and protons (H(+)) remain invisible with X-rays. Moreover, the majority of X-ray structures are determined from cryo-cooled crystals at 100 K, and, although radiation damage can be strongly controlled, especially since the advent of shutterless fast detectors, and by using limited doses and crystal translation at micro-focus beams, radiation damage can still take place. Neutron crystallography therefore remains the only approach where diffraction data can be collected at room temperature without radiation damage issues and the only approach to locate mobile or highly polarized H atoms and protons. Here a review of the current status of sub-atomic X-ray and neutron macromolecular crystallography is given and future prospects for combined approaches are outlined. New results from two metalloproteins, copper nitrite reductase and cytochrome c', are also included, which illustrate the type of information that can be obtained from sub-atomic-resolution (∼0.8 Å) X-ray structures, while also highlighting the need for complementary neutron studies that can provide details of H atoms not provided by X-ray crystallography.
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Affiliation(s)
- Matthew P. Blakeley
- Large-Scale Structures Group, Institut Laue-Langevin, 71 Avenue des Martyrs, Grenoble 38000, France
| | - Samar S. Hasnain
- Molecular Biophysics Group, Institute of Integrative Biology, Faculty of Health and Life Sciences, University of Liverpool, Liverpool L69 7ZX, UK
| | - Svetlana V. Antonyuk
- Molecular Biophysics Group, Institute of Integrative Biology, Faculty of Health and Life Sciences, University of Liverpool, Liverpool L69 7ZX, UK
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24
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Kim JJ, Flueck C, Franz E, Sanabria-Figueroa E, Thompson E, Lorenz R, Bertinetti D, Baker DA, Herberg FW, Kim C. Crystal structures of the carboxyl cGMP binding domain of the Plasmodium falciparum cGMP-dependent protein kinase reveal a novel capping triad crucial for merozoite egress. PLoS Pathog 2015; 11:e1004639. [PMID: 25646845 PMCID: PMC4412288 DOI: 10.1371/journal.ppat.1004639] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2014] [Accepted: 12/20/2014] [Indexed: 01/05/2023] Open
Abstract
The Plasmodium falciparum cGMP-dependent protein kinase (PfPKG) is a key regulator across the malaria parasite life cycle. Little is known about PfPKG’s activation mechanism. Here we report that the carboxyl cyclic nucleotide binding domain functions as a “gatekeeper” for activation by providing the highest cGMP affinity and selectivity. To understand the mechanism, we have solved its crystal structures with and without cGMP at 2.0 and 1.9 Å, respectively. These structures revealed a PfPKG-specific capping triad that forms upon cGMP binding, and disrupting the triad reduces kinase activity by 90%. Furthermore, mutating these residues in the parasite prevents blood stage merozoite egress, confirming the essential nature of the triad in the parasite. We propose a mechanism of activation where cGMP binding allosterically triggers the conformational change at the αC-helix, which bridges the regulatory and catalytic domains, causing the capping triad to form and stabilize the active conformation. Malaria causes up to a million fatalities per year worldwide. Most of these deaths are caused by Plasmodium falciparum, which has a complex life cycle in both humans and mosquitoes. One key regulator of this process is P. falciparum cGMP-dependent protein kinase (PfPKG), the main effector of the cGMP-signaling pathway. Specifically blocking this kinase stops both replication and transmission of the parasites, suggesting that PfPKG is a promising drug target. Here we identified the carboxyl cGMP-binding domain of PfPKG serving as a gatekeeper for activation of the entire kinase by having the highest affinity and selectivity for cGMP. High-resolution crystal structures with and without cGMP allowed us to identify a novel cGMP capping triad that dynamically forms upon binding cGMP and stabilizes the activated conformation. Mutation of the capping triad forming residues not only reduces its kinase activity, but also prevents blood stage merozoite egress, demonstrating its crucial role in PfPKG activation.
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Affiliation(s)
- Jeong Joo Kim
- Department of Pharmacology, Baylor College of Medicine, Houston, Texas, United States of America
- Department of Biochemistry, University of Kassel, Kassel, Hesse, Germany
| | - Christian Flueck
- Faculty of Infectious and Tropical Diseases, London School of Hygiene & Tropical Medicine, London, United Kingdom
| | - Eugen Franz
- Department of Biochemistry, University of Kassel, Kassel, Hesse, Germany
| | | | - Eloise Thompson
- Faculty of Infectious and Tropical Diseases, London School of Hygiene & Tropical Medicine, London, United Kingdom
| | - Robin Lorenz
- Department of Biochemistry, University of Kassel, Kassel, Hesse, Germany
| | - Daniela Bertinetti
- Department of Biochemistry, University of Kassel, Kassel, Hesse, Germany
| | - David A. Baker
- Faculty of Infectious and Tropical Diseases, London School of Hygiene & Tropical Medicine, London, United Kingdom
| | | | - Choel Kim
- Department of Pharmacology, Baylor College of Medicine, Houston, Texas, United States of America
- Verna and Marrs McLean Department of Biochemistry and Molecular Biology, Baylor College of Medicine, Houston, Texas, United States of America
- * E-mail:
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