1
|
Johnston CL, Marzano NR, van Oijen AM, Ecroyd H. Using Single-Molecule Approaches to Understand the Molecular Mechanisms of Heat-Shock Protein Chaperone Function. J Mol Biol 2018; 430:4525-4546. [PMID: 29787765 DOI: 10.1016/j.jmb.2018.05.021] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2018] [Revised: 05/11/2018] [Accepted: 05/13/2018] [Indexed: 02/01/2023]
Abstract
The heat-shock proteins (Hsp) are a family of molecular chaperones, which collectively form a network that is critical for the maintenance of protein homeostasis. Traditional ensemble-based measurements have provided a wealth of knowledge on the function of individual Hsps and the Hsp network; however, such techniques are limited in their ability to resolve the heterogeneous, dynamic and transient interactions that molecular chaperones make with their client proteins. Single-molecule techniques have emerged as a powerful tool to study dynamic biological systems, as they enable rare and transient populations to be identified that would usually be masked in ensemble measurements. Thus, single-molecule techniques are particularly amenable for the study of Hsps and have begun to be used to reveal novel mechanistic details of their function. In this review, we discuss the current understanding of the chaperone action of Hsps and how gaps in the field can be addressed using single-molecule methods. Specifically, this review focuses on the ATP-independent small Hsps and the broader Hsp network and describes how these dynamic systems are amenable to single-molecule techniques.
Collapse
Affiliation(s)
- Caitlin L Johnston
- School of Biological Sciences, University of Wollongong, Wollongong, New South Wales 2522, Australia; Illawarra Health and Medical Research Institute, Wollongong, NSW, 2522, Australia
| | - Nicholas R Marzano
- School of Biological Sciences, University of Wollongong, Wollongong, New South Wales 2522, Australia; Illawarra Health and Medical Research Institute, Wollongong, NSW, 2522, Australia
| | - Antoine M van Oijen
- School of Chemistry, University of Wollongong, Wollongong, New South Wales 2522, Australia; Illawarra Health and Medical Research Institute, Wollongong, NSW, 2522, Australia.
| | - Heath Ecroyd
- School of Biological Sciences, University of Wollongong, Wollongong, New South Wales 2522, Australia; Illawarra Health and Medical Research Institute, Wollongong, NSW, 2522, Australia.
| |
Collapse
|
2
|
Cai Y, Yan W, Xu W, Yin Y, He Y, Wang H, Zhang X. Screening and identification of DnaJ interaction proteins in Streptococcus pneumoniae. Curr Microbiol 2013; 67:732-41. [PMID: 23907491 PMCID: PMC3824243 DOI: 10.1007/s00284-013-0424-4] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2012] [Accepted: 06/16/2013] [Indexed: 11/30/2022]
Abstract
Streptococcus pneumoniae DnaJ is recognized as a virulence factor whose role in pneumococcal virulence remains unclear. Here, we attempted to reveal the contribution of DnaJ in pneumococcal virulence from the identification of its interacting proteins using co-immunoprecipitation method. dnaJ was cloned into plasmid pAE03 generating pAE03-dnaJ-gfp which was used to transform S. pneumoniae D39 strain. Then anti-GFP coated beads were used to capture GFP-coupled proteins from the bacterial lysate. The resulting protein mixtures were subjected to SDS-PAGE and those differential bands were determined by matrix-assisted laser desorption/ionization time of flight mass spectrometry. We finally obtained nine proteins such as DnaK, Gap, Eno, SpxB using this method. Furthermore, to confirm the interaction between DnaJ and these candidates, bacterial two-hybrid system was employed to reveal, for example, the interaction between DnaJ and DnaK, Eno, SpxB. Further protein expression experiments suggested that DnaJ prevented denaturation of Eno and SpxB at high temperature. These results help to understand the role of DnaJ in the pathogenesis of S. pneumoniae.
Collapse
Affiliation(s)
- YingYing Cai
- Key Laboratory of Diagnostic Medicine Designated by the Ministry of Education, Department of Laboratory Medicine, Chongqing Medical University, Chongqing, China
| | | | | | | | | | | | | |
Collapse
|
3
|
Smirnov A, Comte C, Mager-Heckel AM, Addis V, Krasheninnikov IA, Martin RP, Entelis N, Tarassov I. Mitochondrial enzyme rhodanese is essential for 5 S ribosomal RNA import into human mitochondria. J Biol Chem 2010; 285:30792-803. [PMID: 20663881 DOI: 10.1074/jbc.m110.151183] [Citation(s) in RCA: 69] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
5 S rRNA is an essential component of ribosomes. In eukaryotic cells, it is distinguished by particularly complex intracellular traffic, including nuclear export and re-import. The finding that in mammalian cells 5 S rRNA can eventually escape its usual circuit toward nascent ribosomes to get imported into mitochondria has made the scheme more complex, and it has raised questions about both the mechanism of 5 S rRNA mitochondrial targeting and its function inside the organelle. Previously, we showed that import of 5 S rRNA into mitochondria requires unknown cytosolic proteins. Here, one of them was identified as mitochondrial thiosulfate sulfurtransferase, rhodanese. Rhodanese in its misfolded form was found to possess a strong and specific 5 S rRNA binding activity, exploiting sites found earlier to function as signals of 5 S rRNA mitochondrial localization. The interaction with 5 S rRNA occurs cotranslationally and results in formation of a stable complex in which rhodanese is preserved in a compact enzymatically inactive conformation. Human 5 S rRNA in a branched Mg(2+)-free form, upon its interaction with misfolded rhodanese, demonstrates characteristic functional traits of Hsp40 cochaperones implicated in mitochondrial precursor protein targeting, suggesting that it may use this mechanism to ensure its own mitochondrial localization. Finally, silencing of the rhodanese gene caused not only a proportional decrease of 5 S rRNA import but also a general inhibition of mitochondrial translation, indicating the functional importance of the imported 5 S rRNA inside the organelle.
Collapse
Affiliation(s)
- Alexandre Smirnov
- Department of Molecular and Cellular Genetics, UMR 7156, CNRS-University of Strasbourg, Strasbourg 67084, France
| | | | | | | | | | | | | | | |
Collapse
|
4
|
Bischofberger P, Han W, Feifel B, Schönfeld HJ, Christen P. D-Peptides as inhibitors of the DnaK/DnaJ/GrpE chaperone system. J Biol Chem 2003; 278:19044-7. [PMID: 12637539 DOI: 10.1074/jbc.m300922200] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
DnaK, a Hsp70 homolog of Escherichia coli, together with its co-chaperones DnaJ and GrpE protects denatured proteins from aggregation and promotes their refolding by an ATP-consuming mechanism. DnaJ not only stimulates the gamma-phosphate cleavage of DnaK-bound ATP but also binds polypeptide substrates on its own. Unfolded polypeptides, such as denatured luciferase, thus form ternary complexes with DnaJ and DnaK. A previous study has shown that d-peptides compete with l-peptides for the same binding site in DnaJ but do not bind to DnaK (Feifel, B., Schönfeld, H.-J., and Christen, P. (1998) J. Biol. Chem. 273, 11999-12002). Here we report that d-peptides efficiently inhibit the refolding of denatured luciferase by the DnaK/DnaJ/GrpE chaperone system (EC50 = 1-2 microM). The inhibition of the chaperone action is due to the binding of d-peptide to DnaJ (Kd = 1-2 microM), which seems to preclude DnaJ from forming ternary (ATP.DnaK)m.substrate.DnaJn complexes. Apparently, simultaneous binding of DnaJ and DnaK to one and the same target polypeptide is essential for effective chaperone action.
Collapse
Affiliation(s)
- Pius Bischofberger
- Biochemisches Institut der Universität Zürich, Winterthurerstrasse 190, CH-8057, Zürich, Switzerland
| | | | | | | | | |
Collapse
|
5
|
Peroni E, Caminati G, Baglioni P, Nuti F, Chelli M, Papini AM. A new lipophilic fluorescent probe for interaction studies of bioactive lipopeptides with membrane models. Bioorg Med Chem Lett 2002; 12:1731-4. [PMID: 12067548 DOI: 10.1016/s0960-894x(02)00253-6] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
The new fluorescent lipophilic moiety 11-[(7-amino-4-methyl-2-oxo-2H-1-benzopyran-3-acetyl)amino]undecanoic acid (AMCA-omegaAud-OH) was introduced by SPPS at the N-terminus of the immunodominant epitope GpMBP(74-85). FRET experiments using the new fluorescent lipopeptide demonstrate that the peptide interacts with much more affinity with the membrane compared to the lipid free analogue.
Collapse
Affiliation(s)
- Elisa Peroni
- Dipartimento di Chimica Organica Ugo Schiff, Università degli Studi di Firenze, Polo Scientifico, I-50019 Sesto Fiorentino (FI), Italy
| | | | | | | | | | | |
Collapse
|
6
|
Leung WY, Trobridge PA, Haugland RP, Haugland RP, Mao F. 7-Amino-4-methyl-6-sulfocoumarin-3-acetic acid: a novel blue fluorescent dye for protein labeling. Bioorg Med Chem Lett 1999; 9:2229-32. [PMID: 10465551 DOI: 10.1016/s0960-894x(99)00364-9] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
7-Amino-4-methyl-6-sulfocoumarin-3-acetic acid (AMCA-S, also called Alexa 350) 2 was synthesized as a new water-soluble blue fluorescent dye for protein labeling. Compared with its nonsulfonated counterpart (AMCA) 1 the new dye gave significantly higher fluorescence quantum yields on proteins.
Collapse
Affiliation(s)
- W Y Leung
- Molecular Probes, Inc, Eugene, OR 97402, USA
| | | | | | | | | |
Collapse
|
7
|
Abstract
The folding of most newly synthesized proteins in the cell requires the interaction of a variety of protein cofactors known as molecular chaperones. These molecules recognize and bind to nascent polypeptide chains and partially folded intermediates of proteins, preventing their aggregation and misfolding. There are several families of chaperones; those most involved in protein folding are the 40-kDa heat shock protein (HSP40; DnaJ), 60-kDa heat shock protein (HSP60; GroEL), and 70-kDa heat shock protein (HSP70; DnaK) families. The availability of high-resolution structures has facilitated a more detailed understanding of the complex chaperone machinery and mechanisms, including the ATP-dependent reaction cycles of the GroEL and HSP70 chaperones. For both of these chaperones, the binding of ATP triggers a critical conformational change leading to release of the bound substrate protein. Whereas the main role of the HSP70/HSP40 chaperone system is to minimize aggregation of newly synthesized proteins, the HSP60 chaperones also facilitate the actual folding process by providing a secluded environment for individual folding molecules and may also promote the unfolding and refolding of misfolded intermediates.
Collapse
Affiliation(s)
- A L Fink
- Department of Chemistry and Biochemistry, The University of California, Santa Cruz, California, USA
| |
Collapse
|
8
|
Russell R, Wali Karzai A, Mehl AF, McMacken R. DnaJ dramatically stimulates ATP hydrolysis by DnaK: insight into targeting of Hsp70 proteins to polypeptide substrates. Biochemistry 1999; 38:4165-76. [PMID: 10194333 DOI: 10.1021/bi9824036] [Citation(s) in RCA: 74] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Most, if not all, of the cellular functions of Hsp70 proteins require the assistance of a DnaJ homologue, which accelerates the weak intrinsic ATPase activity of Hsp70 and serves as a specificity factor by binding and targeting specific polypeptide substrates for Hsp70 action. We have used pre-steady-state kinetics to investigate the interaction of the Escherichia coli DnaJ and DnaK proteins, and the effects of DnaJ on the ATPase reaction of DnaK. DnaJ accelerates hydrolysis of ATP by DnaK to such an extent that ATP binding by DnaK becomes rate-limiting for hydrolysis. At high concentrations of DnaK under single-turnover conditions, the rate-limiting step is a first-order process, apparently a change of DnaK conformation, that accompanies ATP binding and proceeds at 12-15 min-1 at 25 degrees C and 1-1.5 min-1 at 5 degrees C. By prebinding ATP to DnaK and subsequently adding DnaJ, the effects of this slow step may be bypassed, and the maximal rate-enhancement of DnaJ on the hydrolysis step is approximately 15 000-fold at 5 degrees C. The interaction of DnaJ with DnaK.ATP is likely a rapid equilibrium relative to ATP hydrolysis, and is relatively weak, with a KD of approximately 20 microM at 5 degrees C, and weaker still at 25 degrees C. In the presence of saturating DnaJ, the maximal rate of ATP hydrolysis by DnaK is similar to previously reported rates for peptide release from DnaK.ATP. This suggests that when DnaK encounters a DnaJ-bound polypeptide or protein complex, a significant fraction of such events result in ATP hydrolysis by DnaK and concomitant capture of the polypeptide substrate in a tight complex with DnaK.ADP. Furthermore, a broadly applicable kinetic mechanism for DnaJ-mediated specificity of Hsp70 action arises from these observations, in which the specificity arises largely from the acceleration of the hydrolysis step itself, rather than by DnaJ-dependent modulation of the affinity of Hsp70 for substrate polypeptides.
Collapse
Affiliation(s)
- R Russell
- Department of Biochemistry, Johns Hopkins University, School of Hygiene and Public Health, Baltimore, Maryland 21205, USA
| | | | | | | |
Collapse
|
9
|
Abstract
Proteins that perform their activity within the cytoplasmic membrane or outside this cell boundary must be targeted to the translocation site prior to their insertion and/or translocation. In bacteria, several targeting routes are known; the SecB- and the signal recognition particle-dependent pathways are the best characterized. Recently, evidence for the existence of a third major route, the twin-Arg pathway, was gathered. Proteins that use either one of these three different pathways possess special features that enable their specific interaction with the components of the targeting routes. Such targeting information is often contained in an N-terminal extension, the signal sequence, but can also be found within the mature domain of the targeted protein. Once the nascent chain starts to emerge from the ribosome, competition for the protein between different targeting factors begins. After recognition and binding, the targeting factor delivers the protein to the translocation sites at the cytoplasmic membrane. Only by means of a specific interaction between the targeting component and its receptor is the cargo released for further processing and translocation. This mechanism ensures the high-fidelity targeting of premembrane and membrane proteins to the translocation site.
Collapse
Affiliation(s)
- P Fekkes
- Department of Microbiology and Groningen Biomolecular Sciences and Biotechnology Institute, University of Groningen, 9751 NN Haren, The Netherlands
| | | |
Collapse
|
10
|
Huang K, Flanagan JM, Prestegard JH. The influence of C-terminal extension on the structure of the "J-domain" in E. coli DnaJ. Protein Sci 1999; 8:203-14. [PMID: 10210198 PMCID: PMC2144109 DOI: 10.1110/ps.8.1.203] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
Abstract
Two different recombinant constructs of the N-terminal domain in Escherichia coli DnaJ were uniformly labeled with nitrogen-15 and carbon-13. One, DnaJ(1-78), contains the complete "J-domain," and the other, DnaJ(1-104), contains both the "J-domain" and a conserved "G/F" extension at the C-terminus. The three-dimensional structures of these proteins have been determined by heteronuclear NMR experiments. In both proteins the "J-domain" adopts a compact structure consisting of a helix-turn-helix-loop-helix-turn-helix motif. In contrast, the "G/F" region in DnaJ(1-104) does not fold into a well-defined structure. Nevertheless, the "G/F" region has been found to have an effect on the packing of the helices in the "J-domain" in DnaJ(1-104). Particularly, the interhelical angles between Helix IV and other helices are significantly different in the two structures. In addition, there are some local conformational changes in the loop region connecting the two central helices. These structural differences in the "J-domain" in the presence of the "G/F" region may be related to the observation that DnaJ (1-78) is incapable of stimulating the ATPase activity of the molecular chaperone protein DnaK despite evidence that sites mediating the binding of DnaJ to DnaK are located in the 1-78 segment.
Collapse
Affiliation(s)
- K Huang
- Department of Chemistry, Yale University, New Haven, Connecticut 06520-8107, USA
| | | | | |
Collapse
|
11
|
Pierpaoli EV, Gisler SM, Christen P. Sequence-specific rates of interaction of target peptides with the molecular chaperones DnaK and DnaJ. Biochemistry 1998; 37:16741-8. [PMID: 9843444 DOI: 10.1021/bi981762y] [Citation(s) in RCA: 48] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The kinetics of complex formation between nine different fluorescence-labeled peptides (7-22 amino acid residues) and DnaK (Hsp70 homologue of Escherichia coli) in the nucleotide-free R state and in the ATP-liganded T state were measured. R-state DnaK (1 microM) formed high-affinity complexes (Kd = 0.06-2 microM) and bound all peptides (22-50 nM) in slow one- or two-step processes with apparent rate constants for the first phase, varying only by a maximum factor of 30 (kobs1 = 0.003-0.084 s-1 at pH 7.0 and 25 degreesC). In contrast, the rates of complex formation between DnaK-ATP and the same peptides (Kd = 2.2-107 microM) have been found previously to vary by 4 orders of magnitude [one- or two-step processes with kobs1 = 0.001-7.9 s-1; Gisler, S. M., Pierpaoli E. V., and Christen, P. (1998) J. Mol. Biol. 279, 833-840]. The slow and relatively uniform rates of peptide binding to the R state might be determined by the fraction of time during which the alpha-helical lid above the peptide-binding site is open. The faster and widely divergent rates of binding to the open T state might reflect sequence-specific conformational rearrangements in the peptide-binding site and perhaps of the peptide itself. The different rates of association with DnaK-ATP suggest a kinetic partitioning of target sequences in which only slowly interacting segments of polypeptides are channeled into the chaperone cycle.
Collapse
Affiliation(s)
- E V Pierpaoli
- Biochemisches Institut, Universität Zürich, Switzerland
| | | | | |
Collapse
|
12
|
Yan W, Schilke B, Pfund C, Walter W, Kim S, Craig EA. Zuotin, a ribosome-associated DnaJ molecular chaperone. EMBO J 1998; 17:4809-17. [PMID: 9707440 PMCID: PMC1170810 DOI: 10.1093/emboj/17.16.4809] [Citation(s) in RCA: 122] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Correct folding of newly synthesized polypeptides is thought to be facilitated by Hsp70 molecular chaperones in conjunction with DnaJ cohort proteins. In Saccharomyces cerevisiae, SSB proteins are ribosome-associated Hsp70s which interact with the newly synthesized nascent polypeptide chain. Here we report that the phenotypes of an S.cerevisiae strain lacking the DnaJ-related protein Zuotin (Zuo1) are very similar to those of a strain lacking Ssb, including sensitivities to low temperatures, certain protein synthesis inhibitors and high osmolarity. Zuo1, which has been shown previously to be a nucleic acid-binding protein, is also a ribosome-associated protein localized predominantly in the cytosol. Analysis of zuo1 deletion and truncation mutants revealed a positive correlation between the ribosome association of Zuo1 and its ability to bind RNA. We propose that Zuo1 binds to ribosomes, in part, by interaction with ribosomal RNA and that Zuo1 functions with Ssb as a chaperone on the ribosome.
Collapse
Affiliation(s)
- W Yan
- Department of Biomolecular Chemistry, University of Wisconsin, 1300 University Avenue, Madison, WI 53706, USA
| | | | | | | | | | | |
Collapse
|
13
|
Abstract
The molecular chaperone DnaK, the Hsp70 homolog of Escherichia coli, binds hydrophobic polypeptide segments in extended conformation. The co-chaperone DnaJ (Hsp40) has been reported to bind native and denatured proteins as well as peptides. We tested pseudo-peptides of D-amino acids as ligands for both chaperones. In comparison to the parent all-L peptide, these mimetics had either enantiomorphic side chain positions combined with retained main chain direction (normal all-D peptide) or unchanged side chain topology together with reverse direction of the peptide backbone (retro all-D peptide). The peptides were labeled with acrylodan (a), and their binding to DnaK and DnaJ was monitored by the accompanying increase in fluorescence intensity. The parent all-L peptide a-CALLLSAARR bound to both DnaK (Kd = 0.1 microM) and DnaJ (Kd = 9.2 microM). In contrast, the normal all-D and retro all-D peptides did not bind to DnaK; they bound, however, to DnaJ with Kd values of 6.8 microM and 0.9 microM, respectively. The emission spectra of the DnaJ-bound peptides suggests that DnaJ bound both D-peptides with the same main chain direction as L-peptides. Binding of the normal all-D and all-L peptides inhibited the DnaJ-induced stimulation of DnaK ATPase. However, binding of the retro all-D analog to DnaJ did not impair the stimulation, indicating the existence of separate binding sites for peptides and DnaK.
Collapse
Affiliation(s)
- B Feifel
- Biochemisches Institut der Universität Zürich, CH-8057 Zürich, Switzerland
| | | | | |
Collapse
|
14
|
Nagata H, Hansen WJ, Freeman B, Welch WJ. Mammalian cytosolic DnaJ homologues affect the hsp70 chaperone-substrate reaction cycle, but do not interact directly with nascent or newly synthesized proteins. Biochemistry 1998; 37:6924-38. [PMID: 9578579 DOI: 10.1021/bi980164g] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Members of the hsp70 family of molecular chaperones interact with and stabilize nascent polypeptides during synthesis and/or translocation into organelles. The bacterial hsp70 homologue DnaK requires the DnaJ cofactor for its reaction cycle with polypeptide substrates. DnaJ stimulates the ATPase activity of the DnaK chaperone and thereby is thought to regulate the affinity of DnaK for its protein target. Herein we have analyzed some of the biochemical properties of two mammalian cytosolic DnaJ homologues, the hdj-1 and hdj-2 proteins. We were particularly interested in examining the proposal that DnaJ homologues are the first molecular chaperones to interact directly with nascent polypeptides. Nascent/newly synthesized proteins, nascent polypeptides released from the ribosome by puromycin, or polypeptides misfolded as a result of incorporation of an amino acid analogue were not found in complexes with either of the two HeLa cell DnaJ homologues. We still were unable to demonstrate any interactions between hdj-1p and nascent/newly synthesized proteins even after chemical cross-linking. We did find that hdj-1p, like bacterial DnaJ, stimulated the ATPase activity of hsp70. Stable complex formation between hsp70 and an unfolded polypeptide substrate in vitro was found to be reduced in the presence of hdj-1p and ATP. Thus, while hdj-1p likely does function as a cofactor for the hsp70 chaperone, having effects on hsp70's ATPase activity and conformation/oligomeric structure and the stability of hsp70-substrate complexes, it was not observed to interact directly with nascent/newly synthesized proteins. Rather, hdj-1p likely serves a regulatory role, governing the reaction cycle of hsp70 with polypeptide substrates.
Collapse
Affiliation(s)
- H Nagata
- Department of Medicine, University of California at San Francisco 94143, USA
| | | | | | | |
Collapse
|
15
|
McCarthy D, Kramer G, Hardesty B. Reactivation of thermally inactivated pre-beta-lactamase by DnaK, DnaJ, and GrpE. Protein Sci 1998; 7:1164-71. [PMID: 9605320 PMCID: PMC2144002 DOI: 10.1002/pro.5560070510] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
To understand the role of the 23-amino acid signal sequence in the folding and stability of beta-lactamase, the precursor and a mutant beta-lactamase with a 19-amino acid signal sequence deletion were synthesized in vitro using an Escherichia coli cell-free coupled transcription/translation system. Approximately 30% of the newly synthesized full-length precursor and 60% of the deletion mutant polypeptides were terminated and released from the ribosomes as active enzyme. Activity of the pre-beta-lactamase, but not the mutant, was unstable at 37 degrees C, suggesting that the signal sequence causes the enzyme to unfold. This inactivation was independent of ATP. Pre-beta-lactamase activity was stabilized by lowering the temperature to 30 degrees C. Furthermore, addition of the molecular chaperones DnaK/J and GrpE, in the presence of ATP and Mg2+, restored the activity of the temperature-inactivated precursor. The precursor formed a stable complex with DnaK and GrpE. Both ATP and DnaJ were required for recovery of enzymatic activity, indicating that DnaJ may bind transiently to the complex. These results suggest that the signal sequence of the pre-beta-lactamase causes a temperature-dependent unfolding of the synthesized enzyme and that DnaK/J and GrpE interact with unfolded pre-beta-lactamase to promote refolding of the protein into its native, enzymatically active conformation.
Collapse
Affiliation(s)
- D McCarthy
- Department of Chemistry and Biochemistry, University of Texas at Austin, 78712, USA
| | | | | |
Collapse
|
16
|
Pierpaoli EV, Sandmeier E, Schönfeld HJ, Christen P. Control of the DnaK chaperone cycle by substoichiometric concentrations of the co-chaperones DnaJ and GrpE. J Biol Chem 1998; 273:6643-9. [PMID: 9506960 DOI: 10.1074/jbc.273.12.6643] [Citation(s) in RCA: 69] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The polypeptide binding and release cycle of the molecular chaperone DnaK (Hsp70) of Escherichia coli is regulated by the two co-chaperones DnaJ and GrpE. Here, we show that the DnaJ-triggered conversion of DnaK.ATP (T state) to DnaK.ADP.Pi (R state), as monitored by intrinsic protein fluorescence, is monophasic and occurs simultaneously with ATP hydrolysis. This is in contrast with the T-->R conversion in the absence of DnaJ which is biphasic, the first phase occurring simultaneously with the hydrolysis of ATP (Theyssen, H., Schuster, H.-P., Packschies, L., Bukau, B., and Reinstein, J. (1996) J. Mol. Biol. 263, 657-670). Apparently, DnaJ not only stimulates ATP hydrolysis but also couples it with conformational changes of DnaK. In the absence of GrpE, DnaJ forms a tight ternary complex with peptide.DnaK.ADP.Pi (Kd = 0.14 microM). However, by monitoring complex formation between DnaK (1 microM) and a fluorophore-labeled peptide in the presence of ATP (1 mM), DnaJ (1 microM), and varying concentrations of the ADP/ATP exchange factor GrpE (0.1-3 microM), substoichiometric concentrations of GrpE were found to shift the equilibrium from the slowly binding and releasing, high-affinity R state of DnaK completely to the fast binding and releasing, low-affinity T state and thus to prevent the formation of a long lived ternary DnaJ. substrate.DnaK.ADP.Pi complex. Under in vivo conditions with an estimated chaperone ratio of DnaK:DnaJ:GrpE = 10:1:3, both DnaJ and GrpE appear to control the chaperone cycle by transient interactions with DnaK.
Collapse
Affiliation(s)
- E V Pierpaoli
- Biochemisches Institut, Universität Zürich, Winterthurerstr. 190, CH-8057 Zürich, Switzerland
| | | | | | | |
Collapse
|
17
|
Affiliation(s)
- A N Fedorov
- Center for Macromolecular Design, the Department of Biochemistry and Biophysics, Texas A&M University, College Station, Texas 77843-2128, USA
| | | |
Collapse
|
18
|
Bennett FA, Barlow DJ, Dodoo AN, Hider RC, Lansley AB, Lawrence M, Marriott C, Bansal SS. L-(6,7-dimethoxy-4-coumaryl) alanine: an intrinsic probe for the labelling of peptides. Tetrahedron Lett 1997. [DOI: 10.1016/s0040-4039(97)01753-x] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
|