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Nitika, Zheng B, Ruan L, Kline JT, Omkar S, Sikora J, Texeira Torres M, Wang Y, Takakuwa JE, Huguet R, Klemm C, Segarra VA, Winters MJ, Pryciak PM, Thorpe PH, Tatebayashi K, Li R, Fornelli L, Truman AW. Comprehensive characterization of the Hsp70 interactome reveals novel client proteins and interactions mediated by posttranslational modifications. PLoS Biol 2022; 20:e3001839. [PMID: 36269765 PMCID: PMC9629621 DOI: 10.1371/journal.pbio.3001839] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2022] [Revised: 11/02/2022] [Accepted: 09/21/2022] [Indexed: 01/06/2023] Open
Abstract
Hsp70 interactions are critical for cellular viability and the response to stress. Previous attempts to characterize Hsp70 interactions have been limited by their transient nature and the inability of current technologies to distinguish direct versus bridged interactions. We report the novel use of cross-linking mass spectrometry (XL-MS) to comprehensively characterize the Saccharomyces cerevisiae (budding yeast) Hsp70 protein interactome. Using this approach, we have gained fundamental new insights into Hsp70 function, including definitive evidence of Hsp70 self-association as well as multipoint interaction with its client proteins. In addition to identifying a novel set of direct Hsp70 interactors that can be used to probe chaperone function in cells, we have also identified a suite of posttranslational modification (PTM)-associated Hsp70 interactions. The majority of these PTMs have not been previously reported and appear to be critical in the regulation of client protein function. These data indicate that one of the mechanisms by which PTMs contribute to protein function is by facilitating interaction with chaperones. Taken together, we propose that XL-MS analysis of chaperone complexes may be used as a unique way to identify biologically important PTMs on client proteins.
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Affiliation(s)
- Nitika
- Department of Biological Sciences, The University of North Carolina at Charlotte, Charlotte, North Carolina, United States America
| | - Bo Zheng
- Department of Biological Sciences, The University of North Carolina at Charlotte, Charlotte, North Carolina, United States America
| | - Linhao Ruan
- Center for Cell Dynamics and Department of Cell Biology, Johns Hopkins University School of Medicine, Baltimore, Maryland, United States America
- Biochemistry, Cellular and Molecular Biology (BCMB) Graduate Program, Johns Hopkins University School of Medicine, Baltimore, Maryland, United States America
| | - Jake T. Kline
- Department of Biology, University of Oklahoma, Norman, Oklahoma, United States America
| | - Siddhi Omkar
- Department of Biological Sciences, The University of North Carolina at Charlotte, Charlotte, North Carolina, United States America
| | - Jacek Sikora
- Department of Molecular Biosciences, Department of Chemistry, and the Feinberg School of Medicine, Northwestern University, Evanston, Illinois, United States America
| | - Mara Texeira Torres
- School of Biological and Chemical Sciences, Queen Mary University, London, United Kingdom
| | - Yuhao Wang
- Center for Cell Dynamics and Department of Cell Biology, Johns Hopkins University School of Medicine, Baltimore, Maryland, United States America
- Biochemistry, Cellular and Molecular Biology (BCMB) Graduate Program, Johns Hopkins University School of Medicine, Baltimore, Maryland, United States America
| | - Jade E. Takakuwa
- Department of Biological Sciences, The University of North Carolina at Charlotte, Charlotte, North Carolina, United States America
| | - Romain Huguet
- Thermo Scientific, San Jose, California, United States America
| | - Cinzia Klemm
- School of Biological and Chemical Sciences, Queen Mary University, London, United Kingdom
| | - Verónica A. Segarra
- Departments of Biological Sciences and Chemistry, Goucher College, Baltimore, Maryland, United States America
| | - Matthew J. Winters
- Department of Biochemistry and Molecular Pharmacology, University of Massachusetts Medical School, Worcester, Massachusetts, United States America
| | - Peter M. Pryciak
- Department of Biochemistry and Molecular Pharmacology, University of Massachusetts Medical School, Worcester, Massachusetts, United States America
| | - Peter H. Thorpe
- School of Biological and Chemical Sciences, Queen Mary University, London, United Kingdom
| | - Kazuo Tatebayashi
- Laboratory of Molecular Genetics, Frontier Research Unit, Institute of Medical Science, The University of Tokyo, Tokyo, Japan
- Department of Biological Sciences, Graduate School of Science, The University of Tokyo, Tokyo, Japan
| | - Rong Li
- Center for Cell Dynamics and Department of Cell Biology, Johns Hopkins University School of Medicine, Baltimore, Maryland, United States America
- Biochemistry, Cellular and Molecular Biology (BCMB) Graduate Program, Johns Hopkins University School of Medicine, Baltimore, Maryland, United States America
- Mechanobiology Institute and Department of Biological Sciences, National University of Singapore, Singapore
- Department of Chemical and Biomolecular Engineering, Whiting School of Engineering, Johns Hopkins University, Baltimore, Maryland, United States America
| | - Luca Fornelli
- Department of Biology, University of Oklahoma, Norman, Oklahoma, United States America
| | - Andrew W. Truman
- Department of Biological Sciences, The University of North Carolina at Charlotte, Charlotte, North Carolina, United States America
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Kinetics of the conformational cycle of Hsp70 reveals the importance of the dynamic and heterogeneous nature of Hsp70 for its function. Proc Natl Acad Sci U S A 2020; 117:7814-7823. [PMID: 32198203 PMCID: PMC7148561 DOI: 10.1073/pnas.1914376117] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Heat shock protein 70 kDa (Hsp70) plays a central role in maintaining protein homeostasis. It cooperates with cochaperone Hsp40, which stimulates Hsp70 ATPase activity and presents protein substrates to Hsp70 to assist refolding. The mechanism by which Hsp40 regulates the intramolecular and intermolecular changes of Hsp70 is still largely unknown. Here, by bulk and single-molecule FRET, we report the conformational dynamics of Hsp70 and its regulation by Hsp40 as well as the kinetics of the multistep Hsp70–Hsp40 functional cycle. We show that Hsp40 modulates the conformations of ATP-bound Hsp70 to a domain-undocked ATPase-stimulated state, and facilitates the formation of a heterotetrameric Hsp70–Hsp40 complex. Our findings provide insights into the functional mechanism of this core chaperone machinery. Hsp70 is a conserved molecular chaperone that plays an indispensable role in regulating protein folding, translocation, and degradation. The conformational dynamics of Hsp70 and its regulation by cochaperones are vital to its function. Using bulk and single-molecule fluorescence resonance energy transfer (smFRET) techniques, we studied the interdomain conformational distribution of human stress-inducible Hsp70A1 and the kinetics of conformational changes induced by nucleotide and the Hsp40 cochaperone Hdj1. We found that the conformations between and within the nucleotide- and substrate-binding domains show heterogeneity. The conformational distribution in the ATP-bound state can be induced by Hdj1 to form an “ADP-like” undocked conformation, which is an ATPase-stimulated state. Kinetic measurements indicate that Hdj1 binds to monomeric Hsp70 as the first step, then induces undocking of the two domains and closing of the substrate-binding cleft. Dimeric Hdj1 then facilitates dimerization of Hsp70 and formation of a heterotetrameric Hsp70–Hsp40 complex. Our results provide a kinetic view of the conformational cycle of Hsp70 and reveal the importance of the dynamic nature of Hsp70 for its function.
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Li H, Zhu H, Sarbeng EB, Liu Q, Tian X, Yang Y, Lyons C, Zhou L, Liu Q. An unexpected second binding site for polypeptide substrates is essential for Hsp70 chaperone activity. J Biol Chem 2019; 295:584-596. [PMID: 31806707 DOI: 10.1074/jbc.ra119.009686] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2019] [Revised: 12/02/2019] [Indexed: 12/14/2022] Open
Abstract
Heat shock proteins of 70 kDa (Hsp70s) are ubiquitous and highly conserved molecular chaperones. They play multiple essential roles in assisting with protein folding and maintaining protein homeostasis. Their chaperone activity has been proposed to require several rounds of binding to and release of polypeptide substrates at the substrate-binding domain (SBD) of Hsp70s. All available structures have revealed a single substrate-binding site in the SBD that binds a single segment of an extended polypeptide of 3-4 residues. However, this well-established single peptide-binding site alone has made it difficult to explain the efficient chaperone activity of Hsp70s. In this study, using purified proteins and site-directed mutagenesis, along with fluorescence polarization and luciferase-refolding assays, we report the unexpected discovery of a second peptide-binding site in Hsp70s. More importantly, the biochemical analyses suggested that this novel binding site, named here P2, is essential for Hsp70 chaperone activity. Furthermore, cross-linking and mutagenesis studies indicated that this second binding site is in the SBD adjacent to the first binding site. Taken together, our results suggest that these two essential binding sites of Hsp70s cooperate in protein folding.
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Affiliation(s)
- Hongtao Li
- Department of Physiology and Biophysics, School of Medicine, Virginia Commonwealth University, Richmond, Virginia 23298
| | - Huanyu Zhu
- Department of Physiology and Biophysics, School of Medicine, Virginia Commonwealth University, Richmond, Virginia 23298
| | - Evans Boateng Sarbeng
- Department of Physiology and Biophysics, School of Medicine, Virginia Commonwealth University, Richmond, Virginia 23298
| | - Qingdai Liu
- Department of Physiology and Biophysics, School of Medicine, Virginia Commonwealth University, Richmond, Virginia 23298
| | - Xueli Tian
- Department of Physiology and Biophysics, School of Medicine, Virginia Commonwealth University, Richmond, Virginia 23298
| | - Ying Yang
- Department of Physiology and Biophysics, School of Medicine, Virginia Commonwealth University, Richmond, Virginia 23298
| | - Charles Lyons
- Department of Physiology and Biophysics, School of Medicine, Virginia Commonwealth University, Richmond, Virginia 23298
| | - Lei Zhou
- Department of Physiology and Biophysics, School of Medicine, Virginia Commonwealth University, Richmond, Virginia 23298
| | - Qinglian Liu
- Department of Physiology and Biophysics, School of Medicine, Virginia Commonwealth University, Richmond, Virginia 23298.
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Liu Q, Liang C, Zhou L. Structural and functional analysis of the Hsp70/Hsp40 chaperone system. Protein Sci 2019; 29:378-390. [PMID: 31509306 DOI: 10.1002/pro.3725] [Citation(s) in RCA: 63] [Impact Index Per Article: 12.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2019] [Revised: 08/29/2019] [Accepted: 09/03/2019] [Indexed: 12/22/2022]
Abstract
As one of the most abundant and highly conserved molecular chaperones, the 70-kDa heat shock proteins (Hsp70s) play a key role in maintaining cellular protein homeostasis (proteostasis), one of the most fundamental tasks for every living organism. In this role, Hsp70s are inextricably linked to many human diseases, most notably cancers and neurodegenerative diseases, and are increasingly recognized as important drug targets for developing novel therapeutics for these diseases. Hsp40s are a class of essential and universal partners for Hsp70s in almost all aspects of proteostasis. Thus, Hsp70s and Hsp40s together constitute one of the most important chaperone systems across all kingdoms of life. In recent years, we have witnessed significant progress in understanding the molecular mechanism of this chaperone system through structural and functional analysis. This review will focus on this recent progress, mainly from a structural perspective.
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Affiliation(s)
- Qinglian Liu
- Department of Physiology and Biophysics, Virginia Commonwealth University, Richmond, Virginia
| | - Ce Liang
- Department of Physiology and Biophysics, Virginia Commonwealth University, Richmond, Virginia
| | - Lei Zhou
- Department of Physiology and Biophysics, Virginia Commonwealth University, Richmond, Virginia
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The Link That Binds: The Linker of Hsp70 as a Helm of the Protein's Function. Biomolecules 2019; 9:biom9100543. [PMID: 31569820 PMCID: PMC6843406 DOI: 10.3390/biom9100543] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2019] [Revised: 09/13/2019] [Accepted: 09/21/2019] [Indexed: 12/26/2022] Open
Abstract
The heat shock 70 (Hsp70) family of molecular chaperones plays a central role in maintaining cellular proteostasis. Structurally, Hsp70s are composed of an N-terminal nucleotide binding domain (NBD) which exhibits ATPase activity, and a C-terminal substrate binding domain (SBD). The binding of ATP at the NBD and its subsequent hydrolysis influences the substrate binding affinity of the SBD through allostery. Similarly, peptide binding at the C-terminal SBD stimulates ATP hydrolysis by the N-terminal NBD. Interdomain communication between the NBD and SBD is facilitated by a conserved linker segment. Hsp70s form two main subgroups. Canonical Hsp70 members generally suppress protein aggregation and are also capable of refolding misfolded proteins. Hsp110 members are characterized by an extended lid segment and their function tends to be largely restricted to suppression of protein aggregation. In addition, the latter serve as nucleotide exchange factors (NEFs) of canonical Hsp70s. The linker of the Hsp110 family is less conserved compared to that of the canonical Hsp70 group. In addition, the linker plays a crucial role in defining the functional features of these two groups of Hsp70. Generally, the linker of Hsp70 is quite small and varies in size from seven to thirteen residues. Due to its small size, any sequence variation that Hsp70 exhibits in this motif has a major and unique influence on the function of the protein. Based on sequence data, we observed that canonical Hsp70s possess a linker that is distinct from similar segments present in Hsp110 proteins. In addition, Hsp110 linker motifs from various genera are distinct suggesting that their unique features regulate the flexibility with which the NBD and SBD of these proteins communicate via allostery. The Hsp70 linker modulates various structure-function features of Hsp70 such as its global conformation, affinity for peptide substrate and interaction with co-chaperones. The current review discusses how the unique features of the Hsp70 linker accounts for the functional specialization of this group of molecular chaperones.
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Trcka F, Durech M, Vankova P, Chmelik J, Martinkova V, Hausner J, Kadek A, Marcoux J, Klumpler T, Vojtesek B, Muller P, Man P. Human Stress-inducible Hsp70 Has a High Propensity to Form ATP-dependent Antiparallel Dimers That Are Differentially Regulated by Cochaperone Binding. Mol Cell Proteomics 2019; 18:320-337. [PMID: 30459217 PMCID: PMC6356074 DOI: 10.1074/mcp.ra118.001044] [Citation(s) in RCA: 30] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2018] [Revised: 11/09/2018] [Indexed: 12/23/2022] Open
Abstract
Eukaryotic protein homeostasis (proteostasis) is largely dependent on the action of highly conserved Hsp70 molecular chaperones. Recent evidence indicates that, apart from conserved molecular allostery, Hsp70 proteins have retained and adapted the ability to assemble as functionally relevant ATP-bound dimers throughout evolution. Here, we have compared the ATP-dependent dimerization of DnaK, human stress-inducible Hsp70, Hsc70 and BiP Hsp70 proteins, showing that their dimerization propensities differ, with stress-inducible Hsp70 being predominantly dimeric in the presence of ATP. Structural analyses using hydrogen/deuterium exchange mass spectrometry, native electrospray ionization mass spectrometry and small-angle X-ray scattering revealed that stress-inducible Hsp70 assembles in solution as an antiparallel dimer with the intermolecular interface closely resembling the ATP-bound dimer interfaces captured in DnaK and BiP crystal structures. ATP-dependent dimerization of stress-inducible Hsp70 is necessary for its efficient interaction with Hsp40, as shown by experiments with dimerization-deficient mutants. Moreover, dimerization of ATP-bound Hsp70 is required for its participation in high molecular weight protein complexes detected ex vivo, supporting its functional role in vivo As human cytosolic Hsp70 can interact with tetratricopeptide repeat (TPR) domain containing cochaperones, we tested the interaction of Hsp70 ATP-dependent dimers with Chip and Tomm34 cochaperones. Although Chip associates with intact Hsp70 dimers to form a larger complex, binding of Tomm34 disrupts the Hsp70 dimer and this event plays an important role in Hsp70 activity regulation. In summary, this study provides structural evidence of robust ATP-dependent antiparallel dimerization of human inducible Hsp70 protein and suggests a novel role of TPR domain cochaperones in multichaperone complexes involving Hsp70 ATP-bound dimers.
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Affiliation(s)
- Filip Trcka
- Regional Centre for Applied Molecular Oncology, Masaryk Memorial Cancer Institute, Zluty kopec 7, 656 53 Brno, Czech Republic
| | - Michal Durech
- Regional Centre for Applied Molecular Oncology, Masaryk Memorial Cancer Institute, Zluty kopec 7, 656 53 Brno, Czech Republic
| | - Pavla Vankova
- BioCeV - Institute of Microbiology of the Czech Academy of Sciences, v.v.i., Prumyslova 595, 252 50 Vestec, Czech Republic;; Department of Biochemistry, Faculty of Science, Charles University in Prague, Hlavova 8, 128 43 Prague, Czech Republic
| | - Josef Chmelik
- BioCeV - Institute of Microbiology of the Czech Academy of Sciences, v.v.i., Prumyslova 595, 252 50 Vestec, Czech Republic;; Department of Biochemistry, Faculty of Science, Charles University in Prague, Hlavova 8, 128 43 Prague, Czech Republic
| | - Veronika Martinkova
- Regional Centre for Applied Molecular Oncology, Masaryk Memorial Cancer Institute, Zluty kopec 7, 656 53 Brno, Czech Republic
| | - Jiri Hausner
- BioCeV - Institute of Microbiology of the Czech Academy of Sciences, v.v.i., Prumyslova 595, 252 50 Vestec, Czech Republic;; Department of Biochemistry, Faculty of Science, Charles University in Prague, Hlavova 8, 128 43 Prague, Czech Republic
| | - Alan Kadek
- BioCeV - Institute of Microbiology of the Czech Academy of Sciences, v.v.i., Prumyslova 595, 252 50 Vestec, Czech Republic;; Department of Biochemistry, Faculty of Science, Charles University in Prague, Hlavova 8, 128 43 Prague, Czech Republic
| | - Julien Marcoux
- Institut de Pharmacologie et de Biologie Structurale, Université de Toulouse, CNRS, UPS, Toulouse, France
| | - Tomas Klumpler
- CEITEC-Central European Institute of Technology, Masaryk University, 625 00 Brno, Czech Republic
| | - Borivoj Vojtesek
- Regional Centre for Applied Molecular Oncology, Masaryk Memorial Cancer Institute, Zluty kopec 7, 656 53 Brno, Czech Republic
| | - Petr Muller
- Regional Centre for Applied Molecular Oncology, Masaryk Memorial Cancer Institute, Zluty kopec 7, 656 53 Brno, Czech Republic;.
| | - Petr Man
- BioCeV - Institute of Microbiology of the Czech Academy of Sciences, v.v.i., Prumyslova 595, 252 50 Vestec, Czech Republic;; Department of Biochemistry, Faculty of Science, Charles University in Prague, Hlavova 8, 128 43 Prague, Czech Republic;.
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Durie CL, Duran EC, Lucius AL. Escherichia coli DnaK Allosterically Modulates ClpB between High- and Low-Peptide Affinity States. Biochemistry 2018; 57:3665-3675. [PMID: 29812913 DOI: 10.1021/acs.biochem.8b00045] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
ClpB and DnaKJE provide protection to Escherichia coli cells during extreme environmental stress. Together, this co-chaperone system can resolve protein aggregates, restoring misfolded proteins to their native form and function in solubilizing damaged proteins for removal by the cell's proteolytic systems. DnaK is the component of the KJE system that directly interacts with ClpB. There are many hypotheses for how DnaK affects ClpB-catalyzed disaggregation, each with some experimental support. Here, we build on our recent work characterizing the molecular mechanism of ClpB-catalyzed polypeptide translocation by developing a stopped-flow FRET assay that allows us to detect ClpB's movement on model polypeptide substrates in the absence or presence of DnaK. We find that DnaK induces ClpB to dissociate from the polypeptide substrate. We propose that DnaK acts as a peptide release factor, binding ClpB and causing the ClpB conformation to change to a low-peptide affinity state. Such a role for DnaK would allow ClpB to rebind to another portion of an aggregate and continue nonprocessive translocation to disrupt the aggregate.
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Affiliation(s)
- Clarissa L Durie
- Department of Chemistry , University of Alabama at Birmingham , Birmingham , Alabama 35294-1240 , United States
| | - Elizabeth C Duran
- Department of Chemistry , University of Alabama at Birmingham , Birmingham , Alabama 35294-1240 , United States
| | - Aaron L Lucius
- Department of Chemistry , University of Alabama at Birmingham , Birmingham , Alabama 35294-1240 , United States
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Nitika, Truman AW. Endogenous epitope tagging of heat shock protein 70 isoform Hsc70 using CRISPR/Cas9. Cell Stress Chaperones 2018; 23:347-355. [PMID: 28944418 PMCID: PMC5904078 DOI: 10.1007/s12192-017-0845-2] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2017] [Revised: 09/13/2017] [Accepted: 09/16/2017] [Indexed: 12/31/2022] Open
Abstract
Heat shock protein 70 (Hsp70) is an evolutionarily well-conserved molecular chaperone involved in several cellular processes such as folding of proteins, modulating protein-protein interactions, and transport of proteins across the membrane. Binding partners of Hsp70 (known as "clients") are identified on an individual basis as researchers discover their particular protein of interest binds to Hsp70. A full complement of Hsp70 interactors under multiple stress conditions remains to be determined. A promising approach to characterizing the Hsp70 "interactome" is the use of protein epitope tagging and then affinity purification followed by mass spectrometry (AP-MS/MS). AP-MS analysis is a widely used method to decipher protein-protein interaction networks and identifying protein functions. Conventionally, the proteins are overexpressed ectopically which interferes with protein complex stoichiometry, skewing AP-MS/MS data. In an attempt to solve this issue, we used CRISPR/Cas9-mediated gene editing to integrate a tandem-affinity (TAP) epitope tag into the genomic locus of HSC70. This system offers several benefits over existing expression systems including native expression, no requirement for selection, and homogeneity between cells. This cell line, freely available to chaperone researchers, will aid in small and large-scale protein interaction studies as well as the study of biochemical activities and structure-function relationships of the Hsc70 protein.
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Affiliation(s)
- Nitika
- Department of Biological Sciences, University of North Carolina Charlotte, Charlotte, NC, 28223, USA
| | - Andrew W Truman
- Department of Biological Sciences, University of North Carolina Charlotte, Charlotte, NC, 28223, USA.
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O'Donnell JP, Marsh HM, Sondermann H, Sevier CS. Disrupted Hydrogen-Bond Network and Impaired ATPase Activity in an Hsc70 Cysteine Mutant. Biochemistry 2018; 57:1073-1086. [PMID: 29300467 DOI: 10.1021/acs.biochem.7b01005] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
The ATPase domain of members of the 70 kDa heat shock protein (Hsp70) family shows a high degree of sequence, structural, and functional homology across species. A broadly conserved residue within the Hsp70 ATPase domain that captured our attention is an unpaired cysteine, positioned proximal to the site of nucleotide binding. Prior studies of several Hsp70 family members show this cysteine is not required for Hsp70 ATPase activity, yet select amino acid replacements of the cysteine can dramatically alter ATP hydrolysis. Moreover, post-translational modification of the cysteine has been reported to limit ATP hydrolysis for several Hsp70s. To better understand the underlying mechanism for how perturbation of this noncatalytic residue modulates Hsp70 function, we determined the structure for a cysteine-to-tryptophan mutation in the constitutively expressed, mammalian Hsp70 family member Hsc70. Our work reveals that the steric hindrance produced by a cysteine-to-tryptophan mutation disrupts the hydrogen-bond network within the active site, resulting in a loss of proper catalytic magnesium coordination. We propose that a similarly altered active site is likely observed upon post-translational oxidation. We speculate that the subtle changes we detect in the hydrogen-bonding network may relate to the previously reported observation that cysteine oxidation can influence Hsp70 interdomain communication.
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Affiliation(s)
- John P O'Donnell
- Department of Molecular Medicine, Cornell University , Ithaca, New York 14853, United States
| | - Heather M Marsh
- Department of Molecular Medicine, Cornell University , Ithaca, New York 14853, United States
| | - Holger Sondermann
- Department of Molecular Medicine, Cornell University , Ithaca, New York 14853, United States
| | - Carolyn S Sevier
- Department of Molecular Medicine, Cornell University , Ithaca, New York 14853, United States
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Conformation transitions of the polypeptide-binding pocket support an active substrate release from Hsp70s. Nat Commun 2017; 8:1201. [PMID: 29084938 PMCID: PMC5662698 DOI: 10.1038/s41467-017-01310-z] [Citation(s) in RCA: 44] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2016] [Accepted: 09/07/2017] [Indexed: 12/21/2022] Open
Abstract
Cellular protein homeostasis depends on heat shock proteins 70 kDa (Hsp70s), a class of ubiquitous and highly conserved molecular chaperone. Key to the chaperone activity is an ATP-induced allosteric regulation of polypeptide substrate binding and release. To illuminate the molecular mechanism of this allosteric coupling, here we present a novel crystal structure of an intact human BiP, an essential Hsp70 in ER, in an ATP-bound state. Strikingly, the polypeptide-binding pocket is completely closed, seemingly excluding any substrate binding. Our FRET, biochemical and EPR analysis suggests that this fully closed conformation is the major conformation for the ATP-bound state in solution, providing evidence for an active release of bound polypeptide substrates following ATP binding. The Hsp40 co-chaperone converts this fully closed conformation to an open conformation to initiate productive substrate binding. Taken together, this study provided a mechanistic understanding of the dynamic nature of the polypeptide-binding pocket in the Hsp70 chaperone cycle. Hsp70s are highly conserved molecular chaperones that play multiple essential roles in maintaining cellular protein homeostasis. Here, the authors provide structural evidence for active substrate release by Hsp70s upon ATP binding and provide insight into the molecular mechanism of ATP-driven Hsp70 chaperone activity.
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