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Kelly JJ, Tranter D, Pardon E, Chi G, Kramer H, Happonen L, Knee KM, Janz JM, Steyaert J, Bulawa C, Paavilainen VO, Huiskonen JT, Yue WW. Snapshots of actin and tubulin folding inside the TRiC chaperonin. Nat Struct Mol Biol 2022; 29:420-429. [PMID: 35449234 PMCID: PMC9113939 DOI: 10.1038/s41594-022-00755-1] [Citation(s) in RCA: 21] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2021] [Accepted: 03/01/2022] [Indexed: 01/16/2023]
Abstract
The integrity of a cell's proteome depends on correct folding of polypeptides by chaperonins. The chaperonin TCP-1 ring complex (TRiC) acts as obligate folder for >10% of cytosolic proteins, including he cytoskeletal proteins actin and tubulin. Although its architecture and how it recognizes folding substrates are emerging from structural studies, the subsequent fate of substrates inside the TRiC chamber is not defined. We trapped endogenous human TRiC with substrates (actin, tubulin) and cochaperone (PhLP2A) at different folding stages, for structure determination by cryo-EM. The already-folded regions of client proteins are anchored at the chamber wall, positioning unstructured regions toward the central space to achieve their native fold. Substrates engage with different sections of the chamber during the folding cycle, coupled to TRiC open-and-close transitions. Further, the cochaperone PhLP2A modulates folding, acting as a molecular strut between substrate and TRiC chamber. Our structural snapshots piece together an emerging model of client protein folding within TRiC.
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Affiliation(s)
- John J Kelly
- Centre for Medicines Discovery, Nuffield Department of Clinical Medicine, University of Oxford, Oxford, UK
| | - Dale Tranter
- Institute of Biotechnology, Helsinki Institute of Life Science HiLIFE, University of Helsinki, Helsinki, Finland
| | - Els Pardon
- Structural Biology Brussels, Vrije Universiteit Brussel (VUB), Brussels, Belgium
- VIB-VUB Center for Structural Biology, VIB, Brussels, Belgium
| | - Gamma Chi
- Centre for Medicines Discovery, Nuffield Department of Clinical Medicine, University of Oxford, Oxford, UK
| | - Holger Kramer
- Biological Mass Spectrometry and Proteomics Facility, MRC London Institute of Medical Sciences, Imperial College London, Hammersmith Hospital Campus, London, UK
| | - Lotta Happonen
- Division of Infection Medicine, Department of Clinical Sciences, Lund University, Lund, Sweden
| | - Kelly M Knee
- Pfizer Rare Disease Research Unit, Worldwide Research and Development, Pfizer Inc., Cambridge, MA, USA
| | - Jay M Janz
- Pfizer Rare Disease Research Unit, Worldwide Research and Development, Pfizer Inc., Cambridge, MA, USA
| | - Jan Steyaert
- Structural Biology Brussels, Vrije Universiteit Brussel (VUB), Brussels, Belgium
- VIB-VUB Center for Structural Biology, VIB, Brussels, Belgium
| | - Christine Bulawa
- Pfizer Rare Disease Research Unit, Worldwide Research and Development, Pfizer Inc., Cambridge, MA, USA
| | - Ville O Paavilainen
- Institute of Biotechnology, Helsinki Institute of Life Science HiLIFE, University of Helsinki, Helsinki, Finland
| | - Juha T Huiskonen
- Institute of Biotechnology, Helsinki Institute of Life Science HiLIFE, University of Helsinki, Helsinki, Finland.
- Molecular and Integrative Biosciences Research Programme, Faculty of Biological and Environmental Sciences, University of Helsinki, Helsinki, Finland.
- Division of Structural Biology, Wellcome Centre for Human Genetics, Roosevelt Drive, University of Oxford, Oxford, UK.
| | - Wyatt W Yue
- Centre for Medicines Discovery, Nuffield Department of Clinical Medicine, University of Oxford, Oxford, UK.
- Biosciences Institute, Medical School, Newcastle University, Newcastle upon Tyne, UK.
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2
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Structural and functional dissection of reovirus capsid folding and assembly by the prefoldin-TRiC/CCT chaperone network. Proc Natl Acad Sci U S A 2021; 118:2018127118. [PMID: 33836586 PMCID: PMC7980406 DOI: 10.1073/pnas.2018127118] [Citation(s) in RCA: 20] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Intracellular protein homeostasis is maintained by a network of chaperones that function to fold proteins into their native conformation. The eukaryotic TRiC chaperonin (TCP1-ring complex, also called CCT for cytosolic chaperonin containing TCP1) facilitates folding of a subset of proteins with folding constraints such as complex topologies. To better understand the mechanism of TRiC folding, we investigated the biogenesis of an obligate TRiC substrate, the reovirus σ3 capsid protein. We discovered that the σ3 protein interacts with a network of chaperones, including TRiC and prefoldin. Using a combination of cryoelectron microscopy, cross-linking mass spectrometry, and biochemical approaches, we establish functions for TRiC and prefoldin in folding σ3 and promoting its assembly into higher-order oligomers. These studies illuminate the molecular dynamics of σ3 folding and establish a biological function for TRiC in virus assembly. In addition, our findings provide structural and functional insight into the mechanism by which TRiC and prefoldin participate in the assembly of protein complexes.
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3
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Kabir MA, Uddin W, Narayanan A, Reddy PK, Jairajpuri MA, Sherman F, Ahmad Z. Functional Subunits of Eukaryotic Chaperonin CCT/TRiC in Protein Folding. JOURNAL OF AMINO ACIDS 2011; 2011:843206. [PMID: 22312474 PMCID: PMC3268035 DOI: 10.4061/2011/843206] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/15/2011] [Accepted: 04/05/2011] [Indexed: 12/22/2022]
Abstract
Molecular chaperones are a class of proteins responsible for proper folding of a large number of polypeptides in both prokaryotic and eukaryotic cells. Newly synthesized polypeptides are prone to nonspecific interactions, and many of them make toxic aggregates in absence of chaperones. The eukaryotic chaperonin CCT is a large, multisubunit, cylindrical structure having two identical rings stacked back to back. Each ring is composed of eight different but similar subunits and each subunit has three distinct domains. CCT assists folding of actin, tubulin, and numerous other cellular proteins in an ATP-dependent manner. The catalytic cooperativity of ATP binding/hydrolysis in CCT occurs in a sequential manner different from concerted cooperativity as shown for GroEL. Unlike GroEL, CCT does not have GroES-like cofactor, rather it has a built-in lid structure responsible for closing the central cavity. The CCT complex recognizes its substrates through diverse mechanisms involving hydrophobic or electrostatic interactions. Upstream factors like Hsp70 and Hsp90 also work in a concerted manner to transfer the substrate to CCT. Moreover, prefoldin, phosducin-like proteins, and Bag3 protein interact with CCT and modulate its function for the fine-tuning of protein folding process. Any misregulation of protein folding process leads to the formation of misfolded proteins or toxic aggregates which are linked to multiple pathological disorders.
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Affiliation(s)
- M Anaul Kabir
- Molecular Genetics Laboratory, School of Biotechnology, National Institute of Technology Calicut, Kerala 673601, India
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4
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Jayasinghe M, Tewmey C, Stan G. Versatile substrate protein recognition mechanism of the eukaryotic chaperonin CCT. Proteins 2010; 78:1254-65. [PMID: 19950366 DOI: 10.1002/prot.22644] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Group II chaperonins, found in eukaryotic and archaeal organisms, recognize substrate proteins through diverse mechanisms that involve either hydrophobic- or electrostatic-dominated interactions. This action is distinct from the universal substrate recognition mechanism of group I chaperonins, which bind a wide spectrum of non-native proteins primarily through hydrophobic interactions. We use computational approaches to pinpoint the substrate protein binding sites of the gamma-subunit of the eukaryotic chaperonin CCT and to identify its interactions with the stringent substrate beta-tubulin. Protein-protein docking methods reveal intrinsic binding sites of CCT comprising a helical (HL) region, homologous to the GroEL-binding site, and the helical protrusion (HP) region. We performed molecular dynamics simulations of the solvated CCTgamma apical domain, beta-tubulin peptide-CCTgamma complexes, and isolated beta-tubulin peptides. We find that tubulin binds to CCTgamma through an extensive interface that spans both the HL region and the HP region. HL interactions involve both hydrophobic and electrostatic contacts, while binding to the HP region is stabilized almost exclusively by a salt bridge network. On the basis of additional simulations of a beta-tubulin-CCTgamma complex that involves a reduced interface, centered onto the HP region, we conclude that this salt bridge network is the minimal stabilizing interaction required. Strong conservation of the charged amino acids that participate in the salt bridge network, Arg306 and Glu271, indicates a general mechanism across the nonidentical CCT subunits and group II chaperonins.
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Affiliation(s)
- Manori Jayasinghe
- Department of Chemistry, University of Cincinnati, Cincinnati, Ohio 45221, USA
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5
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Spiess C, Miller EJ, McClellan AJ, Frydman J. Identification of the TRiC/CCT substrate binding sites uncovers the function of subunit diversity in eukaryotic chaperonins. Mol Cell 2006; 24:25-37. [PMID: 17018290 PMCID: PMC3339573 DOI: 10.1016/j.molcel.2006.09.003] [Citation(s) in RCA: 92] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2006] [Revised: 08/11/2006] [Accepted: 09/12/2006] [Indexed: 10/24/2022]
Abstract
The ring-shaped hetero-oligomeric chaperonin TRiC/CCT uses ATP to fold a diverse subset of eukaryotic proteins. To define the basis of TRiC/CCT substrate recognition, we mapped the chaperonin interactions with the VHL tumor suppressor. VHL has two well-defined TRiC binding determinants. Each determinant contacts a specific subset of chaperonin subunits, indicating that TRiC paralogs exhibit distinct but overlapping specificities. The substrate binding site in these subunits localizes to a helical region in the apical domains that is structurally equivalent to that of bacterial chaperonins. Transferring the distal portion of helix 11 between TRiC subunits suffices to transfer specificity for a given substrate motif. We conclude that the architecture of the substrate binding domain is evolutionarily conserved among eukaryotic and bacterial chaperonins. The unique combination of specificity and plasticity in TRiC substrate binding may diversify the range of motifs recognized by this chaperonin and contribute to its unique ability to fold eukaryotic proteins.
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Affiliation(s)
- Christoph Spiess
- Department of Biological Sciences and BioX Program, Stanford University, Stanford, California 94305
| | - Erik J. Miller
- Department of Biological Sciences and BioX Program, Stanford University, Stanford, California 94305
| | - Amie J. McClellan
- Department of Biological Sciences and BioX Program, Stanford University, Stanford, California 94305
| | - Judith Frydman
- Department of Biological Sciences and BioX Program, Stanford University, Stanford, California 94305
- Correspondence:
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Neirynck K, Waterschoot D, Vandekerckhove J, Ampe C, Rommelaere H. Actin Interacts with CCT via Discrete Binding Sites: A Binding transition-release Model for CCT-Mediated Actin Folding. J Mol Biol 2006; 355:124-38. [PMID: 16300788 DOI: 10.1016/j.jmb.2005.10.051] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2005] [Revised: 09/29/2005] [Accepted: 10/18/2005] [Indexed: 11/28/2022]
Abstract
The chaperones prefoldin and the cytosolic chaperonin CCT-containing TCP-1 (CCT) guide the cytoskeletal protein actin to its native conformation. Performing an alanine scan of actin, we identified discrete recognition determinants for CCT interaction. Interestingly, one of these is similar and functional in the non-homologous protein Cdc20, suggesting that some of the binding information in the CCT target proteins is shared. The information in actin for recognition by CCT and for folding is different, as all but one of the mutants in the recognition determinants are folding-competent. In addition, some other actin mutants remain CCT-arrested and are not released in a native conformation, whereas others do fold but remain bound to CAP. Kinetic experiments provide evidence that CCT-mediated folding of non-native actin occurs in at least two steps, in which initially the recognition determinant 245-249 contacts CCT and the other determinants interact at later stages. Actin mutants that are CCT-arrested demonstrate that some regions neighbouring the recognition determinants are involved in modulating the correct folding transitions of actin on CCT, or its release from this chaperonin. Further, we found that the ATP binding of actin is not a prerequisite for its release, and we suggest that CAP may be involved in charging the nucleotide. Based on the kinetics of CCT binding and folding of actin and actin mutants, we propose a multi-step recognition-transition-release model. This also implies that the currently accepted notion of CCT-mediated actin folding is probably more complex.
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Affiliation(s)
- Katrien Neirynck
- Flanders Interuniversity Institute for Biotechnology (VIB 09) and Department of Biochemistry, Faculty of Medicine and Health Sciences, Ghent University. A. Baertsoenkaai 3, 9000 Gent, Belgium
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7
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Bertrand S, Barthelemy I, Oliva MA, Carrascosa JL, Andreu JM, Valpuesta JM. Folding, Stability and Polymerization Properties of FtsZ Chimeras with Inserted Tubulin Loops Involved in the Interaction with the Cytosolic Chaperonin CCT and in Microtubule Formation. J Mol Biol 2005; 346:319-30. [PMID: 15663947 DOI: 10.1016/j.jmb.2004.11.054] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2004] [Revised: 11/11/2004] [Accepted: 11/17/2004] [Indexed: 12/01/2022]
Abstract
To attain its native conformation, the cytoskeletal protein tubulin needs the concourse of several molecular chaperones, among others the cytosolic chaperonin CCT. It has been previously described that denatured tubulin interacts with CCT in a quasi-folded conformation using several loops located throughout its sequence. These loops are also involved in microtubule formation and are absent in its prokaryote homologue FtsZ, which in vitro folds by itself and does not interact with CCT. Several FtsZ/tubulin chimeric proteins were generated by inserting consecutively one, two or three of the CCT-binding domains of tubulin into the corresponding sequence of FtsZ from Methanococccus jannaschii. The insertion of any of the CCT-binding loops generates in the FtsZ/tubulin chimeras the ability to interact with CCT. The accumulation of CCT-binding loops induces in the FtsZ/tubulin chimeras unfolding and refolding properties that are more similar to tubulin than to its prokaryote counterpart. Finally, the insertion of some of these loops generates in the FtsZ/tubulin chimeras more complex polymeric structures than those found for FtsZ. These results reinforce the notion that CCT has coevolved with tubulin to deal with the folding problems encountered by the eukaryotic protein with the appearance of the new sequences involved in microtubule formation.
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Affiliation(s)
- Sara Bertrand
- Centro Nacional de Biotecnología, C.S.I.C Campus de la Universidad Autónoma de Madrid, 28049 Madrid, Spain
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8
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Abstract
Molecular chaperones are a group of proteins that assists in the folding of newly synthesized proteins or in the refolding of denatured proteins. The cytosolic chaperonin-containing t-complex polypeptide 1 (CCT) is a molecular chaperone that plays an important role in the folding of proteins in the eukaryotic cytosol. Actin, tubulin, and several other proteins are known to be folded by CCT, and an estimated 15% of newly translated proteins in mammalian cells are folded with the assistance of CCT. CCT differs from other chaperonin family proteins in its subunit composition, which consists of eight subunit species comprising the CCT 16-mer double-ring-like complex. CCT preferentially recognizes quasinative (or partially folded) intermediates, whereas its Escherichia coli homologue GroEL recognizes more unfolded intermediates, especially those displaying hydrophobic surfaces. Molecular evolutionary analyses have suggested that each subunit species has a specific function in addition to contributing to a common ATPase activity. Consistent with this view, it has been suggested that each subunit recognizes specific substrate proteins (or their parts) and that they collectively modulate the ATPase activity of the complex. The overall expression of CCT in mammalian cells is primarily dependent on cell growth, but each subunit exhibits an individual patterns of expression. Recent progress in CCT research is reviewed, focusing particularly on CCT function and expression. From these observations, the possible roles of the distinct subunits in CCT-assisted folding in the eukaryotic cytosol are discussed.
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Affiliation(s)
- Hiroshi Kubota
- Department of Molecular and Cellular Biology, CREST/JST, Institute for Frontier Medical Sciences, Kyoto University, Kyoto 606-8397, Japan
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9
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Pucciarelli S, Miceli C, Melki R. Heterologous expression and folding analysis of a beta-tubulin isotype from the Antarctic ciliate Euplotes focardii. EUROPEAN JOURNAL OF BIOCHEMISTRY 2002; 269:6271-7. [PMID: 12473123 DOI: 10.1046/j.1432-1033.2002.03346.x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Mammalian tubulins and actins attain their native conformation following interactions with CCT (the cytosolic chaperonin containing t-complex polypeptide 1). To study the beta-tubulin folding in lower eukaryotes, an isotype of beta-tubulin (beta-T1) from the Antarctic ciliate Euplotes focardii, was expressed in Escherichia coli. Folding analysis was performed by incubation of the 35S-labeled, denatured beta-T1 in the presence, or absence, of purified rabbit CCT and cofactor A, a polypeptide that stabilizes folded monomeric beta-tubulin. We show for the first time in protozoa that beta-tubulin folding is assisted by CCT and requires cofactor A. In addition, we observed that E. focardiibeta-T1 competes with human beta5 tubulin isotype for binding to CCT. The affinity of CCT to E. focardiibeta-T1 and beta5 tubulin are compared. Finally, the mitochondrial chaperonin mt-cpn60 binds to beta-T1 but is unable to release it in a native or quasi-native state.
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Affiliation(s)
- Sandra Pucciarelli
- Dipartimento di Biologia Molecolare, Cellulare e Animale, Università di Camerino, Camerino, Italy.
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10
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Andreu JM, Oliva MA, Monasterio O. Reversible unfolding of FtsZ cell division proteins from archaea and bacteria. Comparison with eukaryotic tubulin folding and assembly. J Biol Chem 2002; 277:43262-70. [PMID: 12215443 DOI: 10.1074/jbc.m206723200] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The stability, refolding, and assembly properties of FtsZ cell division proteins from Methanococcus jannaschii and Escherichia coli have been investigated. Their guanidinium chloride unfolding has been studied by circular dichroism spectroscopy. FtsZ from E. coli and tubulin released the bound guanine nucleotide, coinciding with an initial unfolding stage at low denaturant concentrations, followed by unfolding of the apoprotein. FtsZ from M. jannaschii released its nucleotide without any detectable secondary structural change. It unfolded in an apparently two-state transition at larger denaturant concentrations. Isolated FtsZ polypeptide chains were capable of spontaneous refolding and GTP-dependent assembly. The homologous eukaryotic tubulin monomers misfold in solution, but fold within the cytosolic chaperonin CCT. Analysis of the extensive tubulin loop insertions in the FtsZ/tubulin common core and of the intermolecular contacts in model microtubules and tubulin-CCT complexes shows a loop insertion present at every element of lateral protofilament contact and at every contact of tubulin with CCT (except at loop T7). The polymers formed by purified FtsZ have a distinct limited protofilament association in comparison with microtubules. We propose that the loop insertions of tubulin and its CCT-assisted folding coevolved with the lateral association interfaces responsible for extended two-dimensional polymerization into microtubule polymers.
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Affiliation(s)
- Jose Manuel Andreu
- Centro de Investigaciones Biológicas, Consejo Superior de Investigaciones Cientificas, Velázquez 144, 28006 Madrid, Spain.
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11
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Valpuesta JM, Martín-Benito J, Gómez-Puertas P, Carrascosa JL, Willison KR. Structure and function of a protein folding machine: the eukaryotic cytosolic chaperonin CCT. FEBS Lett 2002; 529:11-6. [PMID: 12354605 DOI: 10.1016/s0014-5793(02)03180-0] [Citation(s) in RCA: 175] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Chaperonins are large oligomers made up of two superimposed rings, each enclosing a cavity used for the folding of other proteins. Among the chaperonins, the eukaryotic cytosolic chaperonin CCT is the most complex, not only with regard to its subunit composition but also with respect to its function, still not well understood. Unlike the more well studied eubacterial chaperonin GroEL, which binds any protein that presents stretches of hydrophobic residues, CCT recognises in its substrates specific binding determinants and interacts with them through particular combinations of CCT subunits. Folding then occurs after the conformational changes induced in the chaperonin upon nucleotide binding have occurred, through a mechanism that, although still poorly defined, clearly differs from the one established for GroEL. Although CCT seems to be mainly involved in the folding of actin and tubulin, other substrates involved in various cellular roles are beginning to be characterised, including many WD40-repeat, 7-blade propeller proteins.
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Affiliation(s)
- José M Valpuesta
- Centro Nacional de Biotecnologi;a, C.S.I.C., Campus Universidad Autónoma de Madrid, 28049, Madrid, Spain.
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12
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Cowan NJ, Lewis SA. Type II chaperonins, prefoldin, and the tubulin-specific chaperones. ADVANCES IN PROTEIN CHEMISTRY 2002; 59:73-104. [PMID: 11868281 DOI: 10.1016/s0065-3233(01)59003-8] [Citation(s) in RCA: 57] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Affiliation(s)
- N J Cowan
- Department of Biochemistry, NYU Medical Center, New York, New York 10016, USA
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13
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Soyer-Gobillard MO, Besseau L, Géraud ML, Guillebault D, Albert M, Perret E. Cytoskeleton and mitosis in the dinoflagellate Crypthecodinium cohnii: immunolocalization of P72, an HSP70-related protein. Eur J Protistol 2002. [DOI: 10.1078/0932-4739-00871] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
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14
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Rommelaere H, De Neve M, Neirynck K, Peelaers D, Waterschoot D, Goethals M, Fraeyman N, Vandekerckhove J, Ampe C. Prefoldin recognition motifs in the nonhomologous proteins of the actin and tubulin families. J Biol Chem 2001; 276:41023-8. [PMID: 11535601 DOI: 10.1074/jbc.m106591200] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Nascent actin and tubulin molecules undergo a series of complex interactions with chaperones and are thereby guided to their native conformation. These cytoskeletal proteins have the initial part of the pathway in common: both interact with prefoldin and with the cytosolic chaperonin containing tailless complex polypeptide 1. Little is understood with regard to how these chaperones and, in particular, prefoldin recognize the non-native forms of these target proteins. Using mutagenesis, we provide evidence that beta-actin and alpha-tubulin each have two prefoldin interaction sites. The most amino-terminally located site of both proteins shows striking sequence similarity, although these proteins are nonhomologous. Very similar motifs are present in beta- and gamma-tubulin and in the newly identified prefoldin target protein actin-related protein 1. Actin-related proteins 2 and 3 have related motifs, but these have altered charge properties. The latter two proteins do not bind prefoldin, although we identify them here as target proteins for the cytosolic chaperonin. Actin fragments containing the two prefoldin interaction regions compete efficiently with actin for prefoldin binding. In addition, they also compete with tubulins, suggesting that these target proteins contact similar prefoldin subunits.
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Affiliation(s)
- H Rommelaere
- Flanders Interuniversity Institute for Biotechnology and Department of Biochemistry, Faculty of Medicine, Ghent University, K. L. Ledeganckstraat 35, B-9000 Gent, Belgium.
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15
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Melki R. Review: nucleotide-dependent conformational changes of the chaperonin containing TCP-1. J Struct Biol 2001; 135:170-5. [PMID: 11580266 DOI: 10.1006/jsbi.2001.4388] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Current biochemical and structural studies on the conformational changes induced by the nature of nucleotide bound to the chaperonin containing testis complex polypeptide 1 (CCT) are examined to see how consistent the data are. This exercise suggests that the biochemical and structural data are in good agreement. CCT clearly appears as a folding nano-machine fueled by ATP. A careful comparison of the biochemical and structural data, however, highlights a number of points that remain to be carefully documented in order to better understand the nature of the conformational changes in CCT that yield folded target proteins. Special effort should be made to clearly answer the points listed at the end of this review in order to obtain the dynamic sequence of events yielding folded proteins in the eukaryotic cytoplasm similar to what has been obtained for prokaryotes.
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Affiliation(s)
- R Melki
- Laboratoire d'Enzymologie et Biochimie Structurales, Centre National de la Recherche Scientifique, Avenue de la Terrasse, Gif-sur-Yvette, 91198, France
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16
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Llorca O, Martín-Benito J, Gómez-Puertas P, Ritco-Vonsovici M, Willison KR, Carrascosa JL, Valpuesta JM. Analysis of the interaction between the eukaryotic chaperonin CCT and its substrates actin and tubulin. J Struct Biol 2001; 135:205-18. [PMID: 11580270 DOI: 10.1006/jsbi.2001.4359] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Two mechanisms have thus far been characterized for the assistance by chaperonins of the folding of other proteins. The first and best described is that of the prokaryotic chaperonin GroEL, which interacts with a large spectrum of proteins. GroEL uses a nonspecific mechanism by which any conformation of practically any unfolded polypeptide interacts with it through exposed, hydrophobic residues. ATP binding liberates the substrate in the GroEL cavity where it is given a chance to fold. A second mechanism has been described for the eukaryotic chaperonin CCT, which interacts mainly with the cytoskeletal proteins actin and tubulin. Cryoelectron microscopy and biochemical studies have revealed that both of these proteins interact with CCT in quasi-native, defined conformations. Here we have performed a detailed study of the docking of the actin and tubulin molecules extracted from their corresponding CCT:substrate complexes obtained from cryoelectron microscopy and image processing to localize certain regions in actin and tubulin that are involved in the interaction with CCT. These regions of actin and tubulin, which are not present in their prokaryotic counterparts FtsA and FtsZ, are involved in the polymerization of the two cytoskeletal proteins. These findings suggest coevolution of CCT with actin and tubulin in order to counteract the folding problems associated with the generation in these two cytoskeletal protein families of new domains involved in their polymerization.
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Affiliation(s)
- O Llorca
- Centro Nacional de Biotecnología, C.S.I.C., Campus Universidad Autónoma de Madrid, 28049, Spain
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17
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Kafri G, Willison KR, Horovitz A. Nested allosteric interactions in the cytoplasmic chaperonin containing TCP-1. Protein Sci 2001; 10:445-9. [PMID: 11266630 PMCID: PMC2373951 DOI: 10.1110/ps.44401] [Citation(s) in RCA: 56] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/16/2022]
Abstract
Initial rates of ATP hydrolysis by the chaperonin containing TCP-1 (CCT) from bovine testis were measured as a function of ATP concentration. Two allosteric transitions are observed: one at relatively low concentrations of ATP (<100 microM) and the second at higher concentrations of ATP. The data suggest that CCT has positive intra-ring cooperativity and negative inter-ring cooperativity in ATP hydrolysis, with respect to ATP, as previously observed in the case of GroEL. It is shown that the relatively weak positive intra-ring cooperativity found in the case of CCT may be due to heterogeneity in its subunit composition. Our results suggest that nested allosteric behavior may be common to chaperone double-ring systems.
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Affiliation(s)
- G Kafri
- Department of Structural Biology, Weizmann Institute of Science, Rehovot 76100, Israel
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18
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Ritco-Vonsovici M, Willison KR. Defining the eukaryotic cytosolic chaperonin-binding sites in human tubulins. J Mol Biol 2000; 304:81-98. [PMID: 11071812 DOI: 10.1006/jmbi.2000.4177] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The actins and tubulins are the obligate substrates in vivo of the chaperonin-containing TCP-1 (CCT). The precise elements of recognition between the chaperonin and its substrates remain largely unknown. We have used a solid phase peptide binding assay to screen the human alpha, beta and gamma-tubulin sequences for CCT recognition. Multiple regions seem to be implicated in interactions between tubulins and CCT. These potential CCT-binding sites are highly dispersed throughout the primary sequences of the human tubulins. In addition, using site-directed mutagenesis we assessed the contribution of the selected residues in the C-terminal domain of beta-tubulin to CCT binding. Various hot spots have been identified even though, in each case, their replacement by alanine does not reduce dramatically the total affinity of beta-tubulin for CCT. The CCT-binding information in the tubulins is probably confined to multiple specific regions each having weak or moderate affinity for CCT apical domains. The main binding region seems to be located between residues 263 and 384, but there are no single amino acid residues in this region, which make large contributions to the binding energy, although we have detected a minor contribution by F377. These biochemical results are understandable in the context of our recent structural analysis of CCT-tubulin complexes by cryo-electron microscopy and image reconstruction, which shows that, in one stage of an in vitro binding reaction between apo-CCT and tubulin diluted from guanidinium chloride, ten major, stable contacts between tubulin and CCT are involved. Therefore, specificity is achieved through the co-operation of many specific, albeit weak, interactions.
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Affiliation(s)
- M Ritco-Vonsovici
- Institute of Cancer Research, Chester Beatty Laboratories, 237 Fulham Road, London, SW3 6JB, UK
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