1
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Iljina M, Mazal H, Dayananda A, Zhang Z, Stan G, Riven I, Haran G. Single-molecule FRET probes allosteric effects on protein-translocating pore loops of a AAA+ machine. Biophys J 2024; 123:374-388. [PMID: 38196191 PMCID: PMC10870172 DOI: 10.1016/j.bpj.2024.01.002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2023] [Revised: 11/07/2023] [Accepted: 01/02/2024] [Indexed: 01/11/2024] Open
Abstract
AAA+ proteins (ATPases associated with various cellular activities) comprise a family of powerful ring-shaped ATP-dependent translocases that carry out numerous vital substrate-remodeling functions. ClpB is a AAA+ protein disaggregation machine that forms a two-tiered hexameric ring, with flexible pore loops protruding into its center and binding to substrate proteins. It remains unknown whether these pore loops contribute only passively to substrate-protein threading or have a more active role. Recently, we have applied single-molecule FRET spectroscopy to directly measure the dynamics of substrate-binding pore loops in ClpB. We have reported that the three pore loops of ClpB (PL1-3) undergo large-scale fluctuations on the microsecond timescale that are likely to be mechanistically important for disaggregation. Here, using single-molecule FRET, we study the allosteric coupling between the pore loops and the two nucleotide-binding domains of ClpB (NBD1-2). By mutating the conserved Walker B motifs within the NBDs to abolish ATP hydrolysis, we demonstrate how the nucleotide state of each NBD tunes pore-loop dynamics. This effect is surprisingly long-ranged; in particular, PL2 and PL3 respond differentially to a Walker B mutation in either NBD1 or NBD2, as well as to mutations in both. We characterize the conformational dynamics of pore loops and the allosteric paths connecting NBDs to pore loops by molecular dynamics simulations and find that both principal motions and allosteric paths can be altered by changing the ATPase state of ClpB. Remarkably, PL3, which is highly conserved in AAA+ machines, is found to favor an upward conformation when only NBD1 undergoes ATP hydrolysis but a downward conformation when NBD2 is active. These results explicitly demonstrate a significant long-range allosteric effect of ATP hydrolysis sites on pore-loop dynamics. Pore loops are therefore established as active participants that undergo ATP-dependent conformational changes to translocate substrate proteins through the central pores of AAA+ machines.
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Affiliation(s)
- Marija Iljina
- Department of Chemical and Biological Physics, Weizmann Institute of Science, Rehovot, Israel
| | - Hisham Mazal
- Department of Chemical and Biological Physics, Weizmann Institute of Science, Rehovot, Israel
| | - Ashan Dayananda
- Department of Chemistry, University of Cincinnati, Cincinnati, Ohio
| | - Zhaocheng Zhang
- Department of Chemistry, University of Cincinnati, Cincinnati, Ohio
| | - George Stan
- Department of Chemistry, University of Cincinnati, Cincinnati, Ohio.
| | - Inbal Riven
- Department of Chemical and Biological Physics, Weizmann Institute of Science, Rehovot, Israel
| | - Gilad Haran
- Department of Chemical and Biological Physics, Weizmann Institute of Science, Rehovot, Israel.
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2
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Ghanbarpour A, Cohen SE, Fei X, Kinman LF, Bell TA, Zhang JJ, Baker TA, Davis JH, Sauer RT. A closed translocation channel in the substrate-free AAA+ ClpXP protease diminishes rogue degradation. Nat Commun 2023; 14:7281. [PMID: 37949857 PMCID: PMC10638403 DOI: 10.1038/s41467-023-43145-x] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2022] [Accepted: 11/01/2023] [Indexed: 11/12/2023] Open
Abstract
AAA+ proteases degrade intracellular proteins in a highly specific manner. E. coli ClpXP, for example, relies on a C-terminal ssrA tag or other terminal degron sequences to recognize proteins, which are then unfolded by ClpX and subsequently translocated through its axial channel and into the degradation chamber of ClpP for proteolysis. Prior cryo-EM structures reveal that the ssrA tag initially binds to a ClpX conformation in which the axial channel is closed by a pore-2 loop. Here, we show that substrate-free ClpXP has a nearly identical closed-channel conformation. We destabilize this closed-channel conformation by deleting residues from the ClpX pore-2 loop. Strikingly, open-channel ClpXP variants degrade non-native proteins lacking degrons faster than the parental enzymes in vitro but degraded GFP-ssrA more slowly. When expressed in E. coli, these open channel variants behave similarly to the wild-type enzyme in assays of filamentation and phage-Mu plating but resulted in reduced growth phenotypes at elevated temperatures or when cells were exposed to sub-lethal antibiotic concentrations. Thus, channel closure is an important determinant of ClpXP degradation specificity.
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Affiliation(s)
- Alireza Ghanbarpour
- Department of Biology Massachusetts Institute of Technology Cambridge, Cambridge, MA, 02139, USA
| | - Steven E Cohen
- Department of Biology Massachusetts Institute of Technology Cambridge, Cambridge, MA, 02139, USA
| | - Xue Fei
- Department of Biology Massachusetts Institute of Technology Cambridge, Cambridge, MA, 02139, USA
| | - Laurel F Kinman
- Department of Biology Massachusetts Institute of Technology Cambridge, Cambridge, MA, 02139, USA
| | - Tristan A Bell
- Department of Biology Massachusetts Institute of Technology Cambridge, Cambridge, MA, 02139, USA
| | - Jia Jia Zhang
- Department of Biology Massachusetts Institute of Technology Cambridge, Cambridge, MA, 02139, USA
| | - Tania A Baker
- Department of Biology Massachusetts Institute of Technology Cambridge, Cambridge, MA, 02139, USA
| | - Joseph H Davis
- Department of Biology Massachusetts Institute of Technology Cambridge, Cambridge, MA, 02139, USA.
| | - Robert T Sauer
- Department of Biology Massachusetts Institute of Technology Cambridge, Cambridge, MA, 02139, USA.
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3
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Motone K, Kontogiorgos-Heintz D, Wee J, Kurihara K, Yang S, Roote G, Fang Y, Cardozo N, Nivala J. Multi-pass, single-molecule nanopore reading of long protein strands with single-amino acid sensitivity. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.10.19.563182. [PMID: 37905023 PMCID: PMC10614977 DOI: 10.1101/2023.10.19.563182] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/02/2023]
Abstract
The ability to sequence single protein molecules in their native, full-length form would enable a more comprehensive understanding of proteomic diversity. Current technologies, however, are limited in achieving this goal. Here, we establish a method for long-range, single-molecule reading of intact protein strands on a commercial nanopore sensor array. By using the ClpX unfoldase to ratchet proteins through a CsgG nanopore, we achieve single-amino acid level sensitivity, enabling sequencing of combinations of amino acid substitutions across long protein strands. For greater sequencing accuracy, we demonstrate the ability to reread individual protein molecules, spanning hundreds of amino acids in length, multiple times, and explore the potential for high accuracy protein barcode sequencing. Further, we develop a biophysical model that can simulate raw nanopore signals a priori, based on amino acid volume and charge, enhancing the interpretation of raw signal data. Finally, we apply these methods to examine intact, folded protein domains for complete end-to-end analysis. These results provide proof-of-concept for a platform that has the potential to identify and characterize full-length proteoforms at single-molecule resolution.
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Affiliation(s)
- Keisuke Motone
- Paul. G. Allen School of Computer Science and Engineering, University of Washington, Seattle, WA, USA
- These authors contributed equally: Keisuke Motone, Daphne Kontogiorgos-Heintz
| | - Daphne Kontogiorgos-Heintz
- Paul. G. Allen School of Computer Science and Engineering, University of Washington, Seattle, WA, USA
- These authors contributed equally: Keisuke Motone, Daphne Kontogiorgos-Heintz
| | - Jasmine Wee
- Paul. G. Allen School of Computer Science and Engineering, University of Washington, Seattle, WA, USA
| | - Kyoko Kurihara
- Paul. G. Allen School of Computer Science and Engineering, University of Washington, Seattle, WA, USA
| | - Sangbeom Yang
- Paul. G. Allen School of Computer Science and Engineering, University of Washington, Seattle, WA, USA
| | - Gwendolin Roote
- Paul. G. Allen School of Computer Science and Engineering, University of Washington, Seattle, WA, USA
| | - Yishu Fang
- Paul. G. Allen School of Computer Science and Engineering, University of Washington, Seattle, WA, USA
| | - Nicolas Cardozo
- Molecular Engineering and Science Institute, University of Washington, Seattle, WA, USA
| | - Jeff Nivala
- Paul. G. Allen School of Computer Science and Engineering, University of Washington, Seattle, WA, USA
- Molecular Engineering and Science Institute, University of Washington, Seattle, WA, USA
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4
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Ogbonna EC, Anderson HR, Beardslee PC, Bheemreddy P, Schmitz KR. Interactome Analysis Identifies MSMEI_3879 as a Substrate of Mycolicibacterium smegmatis ClpC1. Microbiol Spectr 2023; 11:e0454822. [PMID: 37341639 PMCID: PMC10433963 DOI: 10.1128/spectrum.04548-22] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2022] [Accepted: 05/31/2023] [Indexed: 06/22/2023] Open
Abstract
The prevalence of drug-resistant Mycobacterium tuberculosis infections has prompted extensive efforts to exploit new drug targets in this globally important pathogen. ClpC1, the unfoldase component of the essential ClpC1P1P2 protease, has emerged as one particularly promising antibacterial target. However, efforts to identify and characterize compounds that impinge on ClpC1 activity are constrained by our limited knowledge of Clp protease function and regulation. To expand our understanding of ClpC1 physiology, we employed a coimmunoprecipitation and mass spectrometry workflow to identify proteins that interact with ClpC1 in Mycolicibacterium smegmatis, a surrogate for M. tuberculosis. We identify a diverse panel of interaction partners, many of which coimmunoprecipitate with both the regulatory N-terminal domain and the ATPase core of ClpC1. Notably, our interactome analysis establishes MSMEI_3879, a truncated gene product unique to M. smegmatis, as a novel proteolytic substrate. Degradation of MSMEI_3879 by ClpC1P1P2 in vitro requires exposure of its N-terminal sequence, reinforcing the idea that ClpC1 selectively recognizes disordered motifs on substrates. Fluorescent substrates incorporating MSMEI_3879 may be useful in screening for novel ClpC1-targeting antibiotics to help address the challenge of M. tuberculosis drug resistance. IMPORTANCE Drug-resistant tuberculosis infections are a major challenge to global public health. Much effort has been invested in identifying new drug targets in the causative pathogen, Mycobacterium tuberculosis. One such target is the ClpC1 unfoldase. Compounds have been identified that kill M. tuberculosis by disrupting ClpC1 activity, yet the physiological function of ClpC1 in cells has remained poorly defined. Here, we identify interaction partners of ClpC1 in a model mycobacterium. By building a broader understanding of the role of this prospective drug target, we can more effectively develop compounds that inhibit its essential cellular activities.
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Affiliation(s)
- Emmanuel C. Ogbonna
- Department of Biological Sciences, University of Delaware, Newark, Delaware, USA
| | - Henry R. Anderson
- Department of Chemistry and Biochemistry, University of Delaware, Newark, Delaware, USA
| | - Patrick C. Beardslee
- Department of Chemistry and Biochemistry, University of Delaware, Newark, Delaware, USA
| | - Priyanka Bheemreddy
- Department of Biological Sciences, University of Delaware, Newark, Delaware, USA
| | - Karl R. Schmitz
- Department of Biological Sciences, University of Delaware, Newark, Delaware, USA
- Department of Chemistry and Biochemistry, University of Delaware, Newark, Delaware, USA
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5
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González-Paz L, Lossada C, Hurtado-León ML, Fernández-Materán FV, Paz JL, Parvizi S, Cardenas Castillo RE, Romero F, Alvarado YJ. Intrinsic Dynamics of the ClpXP Proteolytic Machine Using Elastic Network Models. ACS OMEGA 2023; 8:7302-7318. [PMID: 36873006 PMCID: PMC9979342 DOI: 10.1021/acsomega.2c04347] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/09/2022] [Accepted: 10/25/2022] [Indexed: 06/18/2023]
Abstract
ClpXP complex is an ATP-dependent mitochondrial matrix protease that binds, unfolds, translocates, and subsequently degrades specific protein substrates. Its mechanisms of operation are still being debated, and several have been proposed, including the sequential translocation of two residues (SC/2R), six residues (SC/6R), and even long-pass probabilistic models. Therefore, it has been suggested to employ biophysical-computational approaches that can determine the kinetics and thermodynamics of the translocation. In this sense, and based on the apparent inconsistency between structural and functional studies, we propose to apply biophysical approaches based on elastic network models (ENM) to study the intrinsic dynamics of the theoretically most probable hydrolysis mechanism. The proposed models ENM suggest that the ClpP region is decisive for the stabilization of the ClpXP complex, contributing to the flexibility of the residues adjacent to the pore, favoring the increase in pore size and, therefore, with the energy of interaction of its residues with a larger portion of the substrate. It is predicted that the complex may undergo a stable configurational change once assembled and that the deformability of the system once assembled is oriented, to increase the rigidity of the domains of each region (ClpP and ClpX) and to gain flexibility of the pore. Our predictions could suggest under the conditions of this study the mechanism of the interaction of the system, of which the substrate passes through the unfolding of the pore in parallel with a folding of the bottleneck. The variations in the distance calculated by molecular dynamics could allow the passage of a substrate with a size equivalent to ∼3 residues. The theoretical behavior of the pore and the stability and energy of binding to the substrate based on ENM models suggest that in this system, there are thermodynamic, structural, and configurational conditions that allow a possible translocation mechanism that is not strictly sequential.
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Affiliation(s)
- Lenin González-Paz
- Facultad
Experimental de Ciencias (FEC), Departamento de Biología, Laboratorio
de Genética y Biología Molecular (LGBM), Universidad del Zulia (LUZ), 4001 Maracaibo, Zulia, República Bolivariana
de Venezuela
- Centro
de Biomedicina Molecular (CBM). Laboratorio de Biocomputación
(LB), Instituto Venezolano de Investigaciones
Científicas (IVIC), 4001 Maracaibo, Zulia, República Bolivariana de Venezuela
| | - Carla Lossada
- Centro
de Biomedicina Molecular (CBM). Laboratorio de Biocomputación
(LB), Instituto Venezolano de Investigaciones
Científicas (IVIC), 4001 Maracaibo, Zulia, República Bolivariana de Venezuela
| | - Maria Laura Hurtado-León
- Facultad
Experimental de Ciencias (FEC), Departamento de Biología, Laboratorio
de Genética y Biología Molecular (LGBM), Universidad del Zulia (LUZ), 4001 Maracaibo, Zulia, República Bolivariana
de Venezuela
| | - Francelys V. Fernández-Materán
- Centro
de Biomedicina Molecular (CBM). Laboratorio de Biocomputación
(LB), Instituto Venezolano de Investigaciones
Científicas (IVIC), 4001 Maracaibo, Zulia, República Bolivariana de Venezuela
| | - José Luis Paz
- Departamento
Académico de Química Inorgánica, Facultad de
Química e Ingeniería Química, Universidad Nacional Mayor de San Marcos, 15081 Lima, Perú
| | - Shayan Parvizi
- Pulmonary,
Critical Care and Sleep Medicine, Baylor
College of Medicine, Houston, Texas 77030, United States
| | | | - Freddy Romero
- Pulmonary,
Critical Care and Sleep Medicine, Baylor
College of Medicine, Houston, Texas 77030, United States
| | - Ysaias J. Alvarado
- Centro
de Biomedicina Molecular (CBM), Laboratorio de Química Biofísica
Teórica y Experimental (LQBTE), Instituto
Venezolano de Investigaciones Cientificas (IVIC), 4001 Maracaibo, Zulia, República Bolivariana de Venezuela
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6
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Ye F, Gao F, Liu X, Buck M, Zhang X. Mechanisms of DNA opening revealed in AAA+ transcription complex structures. SCIENCE ADVANCES 2022; 8:eadd3479. [PMID: 36542713 PMCID: PMC9770992 DOI: 10.1126/sciadv.add3479] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 06/06/2022] [Accepted: 11/07/2022] [Indexed: 06/17/2023]
Abstract
Gene transcription is carried out by RNA polymerase (RNAP) and requires the conversion of the initial closed promoter complex, where DNA is double stranded, to a transcription-competent open promoter complex, where DNA is opened up. In bacteria, RNAP relies on σ factors for its promoter specificities. Using a special form of sigma factor (σ54), which forms a stable closed complex and requires its activator that belongs to the AAA+ ATPases (ATPases associated with diverse cellular activities), we obtained cryo-electron microscopy structures of transcription initiation complexes that reveal a previously unidentified process of DNA melting opening. The σ54 amino terminus threads through the locally opened up DNA and then becomes enclosed by the AAA+ hexameric ring in the activator-bound intermediate complex. Our structures suggest how ATP hydrolysis by the AAA+ activator could remove the σ54 inhibition while helping to open up DNA, using σ54 amino-terminal peptide as a pry bar.
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Affiliation(s)
- Fuzhou Ye
- Section of Structural and Synthetic Biology, Department of Infectious Disease, Faculty of Medicine, Imperial College London, South Kensington SW7 2AZ, UK
| | - Forson Gao
- Section of Structural and Synthetic Biology, Department of Infectious Disease, Faculty of Medicine, Imperial College London, South Kensington SW7 2AZ, UK
| | - Xiaojiao Liu
- Section of Structural and Synthetic Biology, Department of Infectious Disease, Faculty of Medicine, Imperial College London, South Kensington SW7 2AZ, UK
| | - Martin Buck
- Department of Life Sciences, Imperial College London, South Kensington SW7 2AZ, UK
| | - Xiaodong Zhang
- Section of Structural and Synthetic Biology, Department of Infectious Disease, Faculty of Medicine, Imperial College London, South Kensington SW7 2AZ, UK
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7
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Sauer RT, Fei X, Bell TA, Baker TA. Structure and function of ClpXP, a AAA+ proteolytic machine powered by probabilistic ATP hydrolysis. Crit Rev Biochem Mol Biol 2022; 57:188-204. [PMID: 34923891 PMCID: PMC9871882 DOI: 10.1080/10409238.2021.1979461] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
ClpXP is an archetypical AAA+ protease, consisting of ClpX and ClpP. ClpX is an ATP-dependent protein unfoldase and polypeptide translocase, whereas ClpP is a self-compartmentalized peptidase. ClpXP is currently the only AAA+ protease for which high-resolution structures exist, the molecular basis of recognition for a protein substrate is understood, extensive biochemical and genetic analysis have been performed, and single-molecule optical trapping has allowed direct visualization of the kinetics of substrate unfolding and translocation. In this review, we discuss our current understanding of ClpXP structure and function, evaluate competing sequential and probabilistic mechanisms of ATP hydrolysis, and highlight open questions for future exploration.
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Affiliation(s)
- Robert T. Sauer
- Department of Biology, Massachusetts Institute of Technology, Cambridge, MA, USA
| | - Xue Fei
- Department of Biology, Massachusetts Institute of Technology, Cambridge, MA, USA
| | - Tristan A. Bell
- Department of Biology, Massachusetts Institute of Technology, Cambridge, MA, USA
| | - Tania A. Baker
- Department of Biology, Massachusetts Institute of Technology, Cambridge, MA, USA
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8
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Mabanglo MF, Houry WA. Recent structural insights into the mechanism of ClpP protease regulation by AAA+ chaperones and small molecules. J Biol Chem 2022; 298:101781. [PMID: 35245501 PMCID: PMC9035409 DOI: 10.1016/j.jbc.2022.101781] [Citation(s) in RCA: 15] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2021] [Revised: 02/17/2022] [Accepted: 02/18/2022] [Indexed: 11/19/2022] Open
Abstract
ClpP is a highly conserved serine protease that is a critical enzyme in maintaining protein homeostasis and is an important drug target in pathogenic bacteria and various cancers. In its functional form, ClpP is a self-compartmentalizing protease composed of two stacked heptameric rings that allow protein degradation to occur within the catalytic chamber. ATPase chaperones such as ClpX and ClpA are hexameric ATPases that form larger complexes with ClpP and are responsible for the selection and unfolding of protein substrates prior to their degradation by ClpP. Although individual structures of ClpP and ATPase chaperones have offered mechanistic insights into their function and regulation, their structures together as a complex have only been recently determined to high resolution. Here, we discuss the cryoelectron microscopy structures of ClpP-ATPase complexes and describe findings previously inaccessible from individual Clp structures, including how a hexameric ATPase and a tetradecameric ClpP protease work together in a functional complex. We then discuss the consensus mechanism for substrate unfolding and translocation derived from these structures, consider alternative mechanisms, and present their strengths and limitations. Finally, new insights into the allosteric control of ClpP gained from studies using small molecules and gain or loss-of-function mutations are explored. Overall, this review aims to underscore the multilayered regulation of ClpP that may present novel ideas for structure-based drug design.
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Affiliation(s)
- Mark F Mabanglo
- Department of Biochemistry, University of Toronto, Toronto, Ontario, Canada
| | - Walid A Houry
- Department of Biochemistry, University of Toronto, Toronto, Ontario, Canada; Department of Chemistry, University of Toronto, Toronto, Ontario, Canada.
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9
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AAA+ protease-adaptor structures reveal altered conformations and ring specialization. Nat Struct Mol Biol 2022; 29:1068-1079. [PMID: 36329286 PMCID: PMC9663308 DOI: 10.1038/s41594-022-00850-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2022] [Accepted: 09/22/2022] [Indexed: 11/06/2022]
Abstract
ClpAP, a two-ring AAA+ protease, degrades N-end-rule proteins bound by the ClpS adaptor. Here we present high-resolution cryo-EM structures of Escherichia coli ClpAPS complexes, showing how ClpA pore loops interact with the ClpS N-terminal extension (NTE), which is normally intrinsically disordered. In two classes, the NTE is bound by a spiral of pore-1 and pore-2 loops in a manner similar to substrate-polypeptide binding by many AAA+ unfoldases. Kinetic studies reveal that pore-2 loops of the ClpA D1 ring catalyze the protein remodeling required for substrate delivery by ClpS. In a third class, D2 pore-1 loops are rotated, tucked away from the channel and do not bind the NTE, demonstrating asymmetry in engagement by the D1 and D2 rings. These studies show additional structures and functions for key AAA+ elements. Pore-loop tucking may be used broadly by AAA+ unfoldases, for example, during enzyme pausing/unloading.
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10
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Acyldepsipeptide activated ClpP1P2 macromolecule of Leptospira, an ideal Achilles' heel to hamper the cell survival and deregulate ClpP proteolytic activity. Res Microbiol 2021; 172:103797. [PMID: 33460738 DOI: 10.1016/j.resmic.2021.103797] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2020] [Revised: 12/30/2020] [Accepted: 01/07/2021] [Indexed: 11/22/2022]
Abstract
Antibiotic acyldepsipeptide (ADEP) targets the bacterial ClpP serine protease and can inhibit the growth of numerous bacterial species by activating/dysregulating the protease activity within the cell. The spirochete Leptospira interrogans harbors two ClpP isoforms (LepClpP1 and LepClpP2). Supplementation of ADEP in the Leptospira growth medium resulted in the inhibition of bacterial growth. The ADEP mediated activation of the LepClpP mixture was dependent on the time allowed for the self-assembly of LepClpP1 and LepClpP2. The dynamic light scattering of the LepClpP mixture in the presence of the ADEP indicated a conformational transformation of the LepClpP machinery. Serine 98, a catalytic triad residue of the LepClpP1 in the LepClpP1P2 heterocomplex, was critical for the ADEP mediated activation. The computational prototype of the LepClpP1P2 structure suggested that the hydrophobic pockets wherein the ADEPs or the physiological chaperone ClpX predominantly dock are exclusively present in the LepClpP2 heptamer. Using the ADEP as a tool, this investigation provides an insight into the molecular function of the LepClpP1P2 in a coalition with its ATPase chaperone LepClpX. The shreds of the evidence illustrated in this investigation verify that ADEP1 possesses the ability to control the LepClpP system in an unconventional approach than the other organisms.
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11
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LaBreck CJ, Trebino CE, Ferreira CN, Morrison JJ, DiBiasio EC, Conti J, Camberg JL. Degradation of MinD oscillator complexes by Escherichia coli ClpXP. J Biol Chem 2020; 296:100162. [PMID: 33288679 PMCID: PMC7857489 DOI: 10.1074/jbc.ra120.013866] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2020] [Revised: 12/01/2020] [Accepted: 12/07/2020] [Indexed: 11/24/2022] Open
Abstract
MinD is a cell division ATPase in Escherichia coli that oscillates from pole to pole and regulates the spatial position of the cell division machinery. Together with MinC and MinE, the Min system restricts assembly of the FtsZ-ring to midcell, oscillating between the opposite ends of the cell and preventing FtsZ-ring misassembly at the poles. Here, we show that the ATP-dependent bacterial proteasome complex ClpXP degrades MinD in reconstituted degradation reactions in vitro and in vivo through direct recognition of the MinD N-terminal region. MinD degradation is enhanced during stationary phase, suggesting that ClpXP regulates levels of MinD in cells that are not actively dividing. ClpXP is a major regulator of growth phase–dependent proteins, and these results suggest that MinD levels are also controlled during stationary phase. In vitro, MinC and MinD are known to coassemble into linear polymers; therefore, we monitored copolymers assembled in vitro after incubation with ClpXP and observed that ClpXP promotes rapid MinCD copolymer destabilization and direct MinD degradation by ClpXP. The N terminus of MinD, including residue Arg 3, which is near the ATP-binding site in sequence, is critical for degradation by ClpXP. Together, these results demonstrate that ClpXP degradation modifies conformational assemblies of MinD in vitro and depresses Min function in vivo during periods of reduced proliferation.
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Affiliation(s)
- Christopher J LaBreck
- Department of Cell & Molecular Biology, The University of Rhode Island, Kingston, Rhode Island, USA
| | - Catherine E Trebino
- Department of Cell & Molecular Biology, The University of Rhode Island, Kingston, Rhode Island, USA
| | - Colby N Ferreira
- Department of Cell & Molecular Biology, The University of Rhode Island, Kingston, Rhode Island, USA
| | - Josiah J Morrison
- Department of Cell & Molecular Biology, The University of Rhode Island, Kingston, Rhode Island, USA
| | - Eric C DiBiasio
- Department of Cell & Molecular Biology, The University of Rhode Island, Kingston, Rhode Island, USA
| | - Joseph Conti
- Department of Cell & Molecular Biology, The University of Rhode Island, Kingston, Rhode Island, USA
| | - Jodi L Camberg
- Department of Cell & Molecular Biology, The University of Rhode Island, Kingston, Rhode Island, USA.
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12
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Multistep substrate binding and engagement by the AAA+ ClpXP protease. Proc Natl Acad Sci U S A 2020; 117:28005-28013. [PMID: 33106413 DOI: 10.1073/pnas.2010804117] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
Escherichia coli ClpXP is one of the most thoroughly studied AAA+ proteases, but relatively little is known about the reactions that allow it to bind and then engage specific protein substrates before the adenosine triphosphate (ATP)-fueled mechanical unfolding and translocation steps that lead to processive degradation. Here, we employ a fluorescence-quenching assay to study the binding of ssrA-tagged substrates to ClpXP. Polyphasic stopped-flow association and dissociation kinetics support the existence of at least three distinct substrate-bound complexes. These kinetic data fit well to a model in which ClpXP and substrate form an initial recognition complex followed by an intermediate complex and then, an engaged complex that is competent for substrate unfolding. The initial association and dissociation steps do not require ATP hydrolysis, but subsequent forward and reverse kinetic steps are accelerated by faster ATP hydrolysis. Our results, together with recent cryo-EM structures of ClpXP bound to substrates, support a model in which the ssrA degron initially binds in the top portion of the axial channel of the ClpX hexamer and then is translocated deeper into the channel in steps that eventually pull the native portion of the substrate against the channel opening. Reversible initial substrate binding allows ClpXP to check potential substrates for degrons, potentially increasing specificity. Subsequent substrate engagement steps allow ClpXP to grip a wide variety of sequences to ensure efficient unfolding and translocation of almost any native substrate.
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13
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Fei X, Bell TA, Barkow SR, Baker TA, Sauer RT. Structural basis of ClpXP recognition and unfolding of ssrA-tagged substrates. eLife 2020; 9:61496. [PMID: 33089779 PMCID: PMC7652416 DOI: 10.7554/elife.61496] [Citation(s) in RCA: 39] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2020] [Accepted: 10/21/2020] [Indexed: 01/05/2023] Open
Abstract
When ribosomes fail to complete normal translation, all cells have mechanisms to ensure degradation of the resulting partial proteins to safeguard proteome integrity. In Escherichia coli and other eubacteria, the tmRNA system rescues stalled ribosomes and adds an ssrA tag or degron to the C-terminus of the incomplete protein, which directs degradation by the AAA+ ClpXP protease. Here, we present cryo-EM structures of ClpXP bound to the ssrA degron. C-terminal residues of the ssrA degron initially bind in the top of an otherwise closed ClpX axial channel and subsequently move deeper into an open channel. For short-degron protein substrates, we show that unfolding can occur directly from the initial closed-channel complex. For longer degron substrates, our studies illuminate how ClpXP transitions from specific recognition into a nonspecific unfolding and translocation machine. Many AAA+ proteases and protein-remodeling motors are likely to employ similar multistep recognition and engagement strategies.
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Affiliation(s)
- Xue Fei
- Departments of Biology, Massachusetts Institute of Technology, Cambridge, United States
| | - Tristan A Bell
- Departments of Biology, Massachusetts Institute of Technology, Cambridge, United States
| | - Sarah R Barkow
- Chemistry, Massachusetts Institute of Technology, Cambridge, United States
| | - Tania A Baker
- Departments of Biology, Massachusetts Institute of Technology, Cambridge, United States
| | - Robert T Sauer
- Departments of Biology, Massachusetts Institute of Technology, Cambridge, United States
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14
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Fei X, Bell TA, Jenni S, Stinson BM, Baker TA, Harrison SC, Sauer RT. Structures of the ATP-fueled ClpXP proteolytic machine bound to protein substrate. eLife 2020; 9:52774. [PMID: 32108573 PMCID: PMC7112951 DOI: 10.7554/elife.52774] [Citation(s) in RCA: 80] [Impact Index Per Article: 20.0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2019] [Accepted: 02/27/2020] [Indexed: 01/11/2023] Open
Abstract
ClpXP is an ATP-dependent protease in which the ClpX AAA+ motor binds, unfolds, and translocates specific protein substrates into the degradation chamber of ClpP. We present cryo-EM studies of the E. coli enzyme that show how asymmetric hexameric rings of ClpX bind symmetric heptameric rings of ClpP and interact with protein substrates. Subunits in the ClpX hexamer assume a spiral conformation and interact with two-residue segments of substrate in the axial channel, as observed for other AAA+ proteases and protein-remodeling machines. Strictly sequential models of ATP hydrolysis and a power stroke that moves two residues of the substrate per translocation step have been inferred from these structural features for other AAA+ unfoldases, but biochemical and single-molecule biophysical studies indicate that ClpXP operates by a probabilistic mechanism in which five to eight residues are translocated for each ATP hydrolyzed. We propose structure-based models that could account for the functional results.
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Affiliation(s)
- Xue Fei
- Department of Biology, Massachusetts Institute of Technology, Cambridge, United States
| | - Tristan A Bell
- Department of Biology, Massachusetts Institute of Technology, Cambridge, United States
| | - Simon Jenni
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, United States
| | - Benjamin M Stinson
- Department of Biology, Massachusetts Institute of Technology, Cambridge, United States
| | - Tania A Baker
- Department of Biology, Massachusetts Institute of Technology, Cambridge, United States.,Howard Hughes Medical Institute, Chevy Chase, United States
| | - Stephen C Harrison
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, United States.,Howard Hughes Medical Institute, Chevy Chase, United States
| | - Robert T Sauer
- Department of Biology, Massachusetts Institute of Technology, Cambridge, United States
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15
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The molecular principles governing the activity and functional diversity of AAA+ proteins. Nat Rev Mol Cell Biol 2019; 21:43-58. [PMID: 31754261 DOI: 10.1038/s41580-019-0183-6] [Citation(s) in RCA: 118] [Impact Index Per Article: 23.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/26/2019] [Indexed: 12/26/2022]
Abstract
ATPases associated with diverse cellular activities (AAA+ proteins) are macromolecular machines that convert the chemical energy contained in ATP molecules into powerful mechanical forces to remodel a vast array of cellular substrates, including protein aggregates, macromolecular complexes and polymers. AAA+ proteins have key functionalities encompassing unfolding and disassembly of such substrates in different subcellular localizations and, hence, power a plethora of fundamental cellular processes, including protein quality control, cytoskeleton remodelling and membrane dynamics. Over the past 35 years, many of the key elements required for AAA+ activity have been identified through genetic, biochemical and structural analyses. However, how ATP powers substrate remodelling and whether a shared mechanism underlies the functional diversity of the AAA+ superfamily were uncertain. Advances in cryo-electron microscopy have enabled high-resolution structure determination of AAA+ proteins trapped in the act of processing substrates, revealing a conserved core mechanism of action. It has also become apparent that this common mechanistic principle is structurally adjusted to carry out a diverse array of biological functions. Here, we review how substrate-bound structures of AAA+ proteins have expanded our understanding of ATP-driven protein remodelling.
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16
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Staphylococcus aureus ClpX localizes at the division septum and impacts transcription of genes involved in cell division, T7-secretion, and SaPI5-excision. Sci Rep 2019; 9:16456. [PMID: 31712583 PMCID: PMC6848492 DOI: 10.1038/s41598-019-52823-0] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2019] [Accepted: 10/12/2019] [Indexed: 11/25/2022] Open
Abstract
In all living cells, molecular chaperones are essential for facilitating folding and unfolding of proteins. ClpX is a highly conserved ATP-dependent chaperone that besides functioning as a classical chaperone can associate with ClpP to form the ClpXP protease. To investigate the relative impact of the ClpXP protease and the ClpX chaperone in cell physiology of the important pathogenic bacterium Staphylococcus aureus, we assessed the transcriptional changes induced by inactivating only ClpXP, or by completely deleting ClpX. This analysis revealed that ClpX has a profound impact on S. aureus cell physiology that is mediated primarily via ClpXP-dependent pathways. As an example, ClpX impacts expression of virulence genes entirely via ClpXP-dependent mechanisms. Furthermore, ClpX controls a high number of genes and sRNAs via pathways involving both ClpXP protease and ClpX chaperone activities; an interesting example being genes promoting excision and replication of the pathogenicity island SaPI5. Independently of ClpP, ClpX, impacts transcription of only a restricted number of genes involved in peptidoglycan synthesis, cell division, and type seven secretion. Finally, we demonstrate that ClpX localizes in single foci in close proximity to the division septum lending support to the idea that ClpX plays a role in S. aureus cell division.
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17
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Bell TA, Baker TA, Sauer RT. Interactions between a subset of substrate side chains and AAA+ motor pore loops determine grip during protein unfolding. eLife 2019; 8:46808. [PMID: 31251172 PMCID: PMC6677533 DOI: 10.7554/elife.46808] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2019] [Accepted: 06/27/2019] [Indexed: 01/04/2023] Open
Abstract
Most AAA+ remodeling motors denature proteins by pulling on the peptide termini of folded substrates, but it is not well-understood how motors produce grip when resisting a folded domain. Here, at single amino-acid resolution, we identify the determinants of grip by measuring how substrate tail sequences alter the unfolding activity of the unfoldase-protease ClpXP. The seven amino acids abutting a stable substrate domain are key, with residues 2-6 forming a core that contributes most significantly to grip. ClpX grips large hydrophobic and aromatic side chains strongly and small, polar, or charged side chains weakly. Multiple side chains interact with pore loops synergistically to strengthen grip. In combination with recent structures, our results support a mechanism in which unfolding grip is primarily mediated by non-specific van der Waal's interactions between core side chains of the substrate tail and a subset of YVG loops at the top of the ClpX axial pore.
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Affiliation(s)
- Tristan A Bell
- Department of BiologyMassachusetts Institute of TechnologyCambridgeUnited States
| | - Tania A Baker
- Department of BiologyMassachusetts Institute of TechnologyCambridgeUnited States
- Howard Hughes Medical Institute, Massachusetts Institute of TechnologyCambridgeUnited States
| | - Robert T Sauer
- Department of BiologyMassachusetts Institute of TechnologyCambridgeUnited States
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18
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Abstract
Proteomic analyses provide essential information on molecular pathways of cellular systems and the state of a living organism. Mass spectrometry is currently the first choice for proteomic analysis. However, the requirement for a large amount of sample renders a small-scale proteomics study challenging. Here, we demonstrate a proof of concept of single-molecule FRET-based protein fingerprinting. We harnessed the AAA+ protease ClpXP to scan peptides. By using donor fluorophore-labeled ClpP, we sequentially read out FRET signals from acceptor-labeled amino acids of peptides. The repurposed ClpXP exhibits unidirectional processing with high processivity and has the potential to detect low-abundance proteins. Our technique is a promising approach for sequencing protein substrates using a small amount of sample.
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19
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Stahlhut SG, Alqarzaee AA, Jensen C, Fisker NS, Pereira AR, Pinho MG, Thomas VC, Frees D. The ClpXP protease is dispensable for degradation of unfolded proteins in Staphylococcus aureus. Sci Rep 2017; 7:11739. [PMID: 28924169 PMCID: PMC5603545 DOI: 10.1038/s41598-017-12122-y] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2017] [Accepted: 09/04/2017] [Indexed: 01/01/2023] Open
Abstract
In living cells intracellular proteolysis is crucial for protein homeostasis, and ClpP proteases are conserved between eubacteria and the organelles of eukaryotic cells. In Staphylococcus aureus, ClpP associates to the substrate specificity factors, ClpX and ClpC forming two ClpP proteases, ClpXP and ClpCP. To address how individual ClpP proteases impact cell physiology, we constructed a S. aureus mutant expressing ClpX with an I265E substitution in the ClpP recognition tripeptide of ClpX. This mutant cannot degrade established ClpXP substrates confirming that the introduced amino acid substitution abolishes ClpXP activity. Phenotypic characterization of this mutant showed that ClpXP activity controls cell size and is required for growth at low temperature. Cells expressing the ClpXI265E variant, in contrast to cells lacking ClpP, are not sensitive to heat-stress and do not accumulate protein aggregates showing that ClpXP is dispensable for degradation of unfolded proteins in S. aureus. Consistent with this finding, transcriptomic profiling revealed strong induction of genes responding to protein folding stress in cells devoid of ClpP, but not in cells lacking only ClpXP. In the latter cells, highly upregulated loci include the urease operon, the pyrimidine biosynthesis operon, the betA-betB operon, and the pathogenicity island, SaPI5, while virulence genes were dramatically down-regulated.
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Affiliation(s)
- Steen G Stahlhut
- Department of Veterinary Disease Biology, University of Copenhagen, 1870, Frederiksberg C, Denmark
| | - Abdulelah A Alqarzaee
- Center for Staphylococcal Research, Department of Pathology and Microbiology, University of Nebraska Medical Center, Omaha, Nebraska, 68198, USA
| | - Camilla Jensen
- Department of Veterinary Disease Biology, University of Copenhagen, 1870, Frederiksberg C, Denmark
| | - Niclas S Fisker
- Department of Veterinary Disease Biology, University of Copenhagen, 1870, Frederiksberg C, Denmark
| | - Ana R Pereira
- Bacterial Cell Biology, Instituto de Tecnologia Química e Biológica António Xavier, Universidade Nova de Lisboa, Oeiras, Portugal
| | - Mariana G Pinho
- Bacterial Cell Biology, Instituto de Tecnologia Química e Biológica António Xavier, Universidade Nova de Lisboa, Oeiras, Portugal
| | - Vinai Chittezham Thomas
- Center for Staphylococcal Research, Department of Pathology and Microbiology, University of Nebraska Medical Center, Omaha, Nebraska, 68198, USA
| | - Dorte Frees
- Department of Veterinary Disease Biology, University of Copenhagen, 1870, Frederiksberg C, Denmark.
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20
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Effect of directional pulling on mechanical protein degradation by ATP-dependent proteolytic machines. Proc Natl Acad Sci U S A 2017; 114:E6306-E6313. [PMID: 28724722 DOI: 10.1073/pnas.1707794114] [Citation(s) in RCA: 36] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
AAA+ proteases and remodeling machines couple hydrolysis of ATP to mechanical unfolding and translocation of proteins following recognition of sequence tags called degrons. Here, we use single-molecule optical trapping to determine the mechanochemistry of two AAA+ proteases, Escherichia coli ClpXP and ClpAP, as they unfold and translocate substrates containing multiple copies of the titinI27 domain during degradation initiated from the N terminus. Previous studies characterized degradation of related substrates with C-terminal degrons. We find that ClpXP and ClpAP unfold the wild-type titinI27 domain and a destabilized variant far more rapidly when pulling from the N terminus, whereas translocation speed is reduced only modestly in the N-to-C direction. These measurements establish the role of directionality in mechanical protein degradation, show that degron placement can change whether unfolding or translocation is rate limiting, and establish that one or a few power strokes are sufficient to unfold some protein domains.
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21
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Kuhlmann NJ, Chien P. Selective adaptor dependent protein degradation in bacteria. Curr Opin Microbiol 2017; 36:118-127. [PMID: 28458096 DOI: 10.1016/j.mib.2017.03.013] [Citation(s) in RCA: 31] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2017] [Revised: 03/12/2017] [Accepted: 03/29/2017] [Indexed: 11/30/2022]
Abstract
Energy dependent proteolysis is essential for all life, but uncontrolled degradation leads to devastating consequences. In bacteria, oligomeric AAA+ proteases are responsible for controlling protein destruction and are regulated in part by adaptor proteins. Adaptors are regulatory factors that shape protease substrate choice by either restricting or enhancing substrate recognition in several ways. In some cases, protease activity or assembly itself requires adaptor binding. Adaptors can also alter specificity by acting as scaffolds to tether particular substrates to already active proteases. Finally, hierarchical assembly of adaptors can use combinations of several activities to enhance the protease's selectivity. Because the lifetime of the constituent proteins directly affects the duration of a particular signaling pathway, regulated proteolysis impacts almost all cellular responses. In this review, we describe recent progress in regulated protein degradation, focusing on fundamental principles of adaptors and how they perform critical biological functions, such as promoting cell cycle progression and quality control.
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Affiliation(s)
- Nathan J Kuhlmann
- Molecular and Cellular Biology Graduate Program, University of Massachusetts, Amherst, United States
| | - Peter Chien
- Molecular and Cellular Biology Graduate Program, University of Massachusetts, Amherst, United States; Department of Biochemistry and Molecular Biology, University of Massachusetts, Amherst, United States.
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22
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Bittner LM, Arends J, Narberhaus F. Mini review: ATP-dependent proteases in bacteria. Biopolymers 2017; 105:505-17. [PMID: 26971705 DOI: 10.1002/bip.22831] [Citation(s) in RCA: 30] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2016] [Revised: 02/11/2016] [Accepted: 03/07/2016] [Indexed: 01/22/2023]
Abstract
AAA(+) proteases are universal barrel-like and ATP-fueled machines preventing the accumulation of aberrant proteins and regulating the proteome according to the cellular demand. They are characterized by two separate operating units, the ATPase and peptidase domains. ATP-dependent unfolding and translocation of a substrate into the proteolytic chamber is followed by ATP-independent degradation. This review addresses the structure and function of bacterial AAA(+) proteases with a focus on the ATP-driven mechanisms and the coordinated movements in the complex mainly based on the knowledge of ClpXP. We conclude by discussing strategies how novel protease substrates can be trapped by mutated AAA(+) protease variants. © 2016 Wiley Periodicals, Inc. Biopolymers 105: 505-517, 2016.
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Affiliation(s)
| | - Jan Arends
- Microbial Biology, Ruhr University Bochum, Bochum, Germany
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23
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Bacterial Proteasomes: Mechanistic and Functional Insights. Microbiol Mol Biol Rev 2016; 81:81/1/e00036-16. [PMID: 27974513 DOI: 10.1128/mmbr.00036-16] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
Regulated proteolysis is essential for the normal physiology of all organisms. While all eukaryotes and archaea use proteasomes for protein degradation, only certain orders of bacteria have proteasomes, whose functions are likely as diverse as the species that use them. In this review, we discuss the most recent developments in the understanding of how proteins are targeted to proteasomes for degradation, including ATP-dependent and -independent mechanisms, and the roles of proteasome-dependent degradation in protein quality control and the regulation of cellular physiology. Furthermore, we explore newly established functions of proteasome system accessory factors that function independently of proteolysis.
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24
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Olivares AO, Baker TA, Sauer RT. Mechanistic insights into bacterial AAA+ proteases and protein-remodelling machines. Nat Rev Microbiol 2015; 14:33-44. [PMID: 26639779 DOI: 10.1038/nrmicro.2015.4] [Citation(s) in RCA: 195] [Impact Index Per Article: 21.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
To maintain protein homeostasis, AAA+ proteolytic machines degrade damaged and unneeded proteins in bacteria, archaea and eukaryotes. This process involves the ATP-dependent unfolding of a target protein and its subsequent translocation into a self-compartmentalized proteolytic chamber. Related AAA+ enzymes also disaggregate and remodel proteins. Recent structural and biochemical studies, in combination with direct visualization of unfolding and translocation in single-molecule experiments, have illuminated the molecular mechanisms behind these processes and suggest how remodelling of macromolecular complexes by AAA+ enzymes could occur without global denaturation. In this Review, we discuss the structural and mechanistic features of AAA+ proteases and remodelling machines, focusing on the bacterial ClpXP and ClpX as paradigms. We also consider the potential of these enzymes as antibacterial targets and outline future challenges for the field.
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Affiliation(s)
- Adrian O Olivares
- Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
| | - Tania A Baker
- Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
| | - Robert T Sauer
- Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
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25
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Al-Furoukh N, Ianni A, Nolte H, Hölper S, Krüger M, Wanrooij S, Braun T. ClpX stimulates the mitochondrial unfolded protein response (UPRmt) in mammalian cells. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2015; 1853:2580-91. [DOI: 10.1016/j.bbamcr.2015.06.016] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/10/2015] [Revised: 06/09/2015] [Accepted: 06/27/2015] [Indexed: 02/06/2023]
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26
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Iosefson O, Olivares AO, Baker TA, Sauer RT. Dissection of Axial-Pore Loop Function during Unfolding and Translocation by a AAA+ Proteolytic Machine. Cell Rep 2015; 12:1032-41. [PMID: 26235618 DOI: 10.1016/j.celrep.2015.07.007] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2015] [Revised: 06/30/2015] [Accepted: 07/01/2015] [Indexed: 10/23/2022] Open
Abstract
In the axial channels of ClpX and related hexameric AAA+ protein-remodeling rings, the pore-1 loops are thought to play important roles in engaging, mechanically unfolding, and translocating protein substrates. How these loops perform these functions and whether they also prevent substrate dissociation to ensure processive degradation by AAA+ proteases are open questions. Using ClpX pore-1-loop variants, single-molecule force spectroscopy, and ensemble assays, we find that the six pore-1 loops function synchronously to grip and unfold protein substrates during a power stroke but are not important in preventing substrate slipping between power strokes. The importance of grip strength is task dependent. ClpX variants with multiple mutant pore-1 loops translocate substrates as well as the wild-type enzyme against a resisting force but show unfolding defects and a higher frequency of substrate release. These problems are magnified for more mechanically stable target proteins, supporting a threshold model of substrate gripping.
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Affiliation(s)
- Ohad Iosefson
- Department of Biology, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
| | - Adrian O Olivares
- Department of Biology, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
| | - Tania A Baker
- Department of Biology, Massachusetts Institute of Technology, Cambridge, MA 02139, USA; Howard Hughes Medical Institute, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
| | - Robert T Sauer
- Department of Biology, Massachusetts Institute of Technology, Cambridge, MA 02139, USA.
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27
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Yang B, Stjepanovic G, Shen Q, Martin A, Hurley JH. Vps4 disassembles an ESCRT-III filament by global unfolding and processive translocation. Nat Struct Mol Biol 2015; 22:492-8. [PMID: 25938660 PMCID: PMC4456219 DOI: 10.1038/nsmb.3015] [Citation(s) in RCA: 69] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2014] [Accepted: 03/26/2015] [Indexed: 11/09/2022]
Abstract
The AAA+ ATPase Vps4 disassembles ESCRT-III and is essential for HIV-1 budding and other pathways. Vps4 is a paradigmatic member of a class of hexameric AAA+ ATPases that disassemble protein complexes without degradation. To distinguish between local displacement versus global unfolding mechanisms for complex disassembly, we carried out hydrogen-deuterium exchange during Saccharomyces cerevisiae Vps4 disassembly of of a chimeric Vps24-2 ESCRT-III filament. EX1 exchange behavior shows that Vps4 completely unfolds ESCRT-III substrates on a time scale consistent with the disassembly reaction. The established unfoldase ClpX showed the same pattern, demonstrating a common unfolding mechanism. Vps4 hexamers containing a single cysteine residue in the pore loops were cross-linked to ESCRT-III subunits containing unique cysteine within the folded core domain. These data support a mechanism in which Vps4 disassembles its substrates by completely unfolding them and threading them through the central pore.
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Affiliation(s)
- Bei Yang
- Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, California, USA
| | - Goran Stjepanovic
- Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, California, USA
| | - Qingtao Shen
- Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, California, USA
| | - Andreas Martin
- Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, California, USA
| | - James H Hurley
- 1] Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, California, USA. [2] Life Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California, USA
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28
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Stochastic but highly coordinated protein unfolding and translocation by the ClpXP proteolytic machine. Cell 2015; 158:647-58. [PMID: 25083874 DOI: 10.1016/j.cell.2014.05.043] [Citation(s) in RCA: 104] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2014] [Revised: 04/18/2014] [Accepted: 05/13/2014] [Indexed: 10/25/2022]
Abstract
ClpXP and other AAA+ proteases recognize, mechanically unfold, and translocate target proteins into a chamber for proteolysis. It is not known whether these remarkable molecular machines operate by a stochastic or sequential mechanism or how power strokes relate to the ATP-hydrolysis cycle. Single-molecule optical trapping allows ClpXP unfolding to be directly visualized and reveals translocation steps of ∼1-4 nm in length, but how these activities relate to solution degradation and the physical properties of substrate proteins remains unclear. By studying single-molecule degradation using different multidomain substrates and ClpXP variants, we answer many of these questions and provide evidence for stochastic unfolding and translocation. We also present a mechanochemical model that accounts for single-molecule, biochemical, and structural results for our observation of enzymatic memory in translocation stepping, for the kinetics of translocation steps of different sizes, and for probabilistic but highly coordinated subunit activity within the ClpX ring.
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29
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Coordinated gripping of substrate by subunits of a AAA+ proteolytic machine. Nat Chem Biol 2015; 11:201-6. [PMID: 25599533 PMCID: PMC4333055 DOI: 10.1038/nchembio.1732] [Citation(s) in RCA: 52] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2014] [Accepted: 11/10/2014] [Indexed: 11/08/2022]
Abstract
Hexameric ATP-dependent proteases and protein remodeling machines use conserved loops that line the axial pore to apply force to substrates during the mechanical processes of protein unfolding and translocation. Whether loops from multiple subunits act independently or coordinately in these processes is a critical aspect of the mechanism but is currently unknown for any AAA+ machine. By studying covalently linked hexamers of the Escherichia coli ClpX unfoldase bearing different numbers and configurations of wild-type and mutant pore loops, we show that loops function synergistically, and the number of wild-type loops required for efficient degradation is dependent on the stability of the protein substrate. Our results support a mechanism in which a power stroke initiated in one subunit of the ClpX hexamer results in the concurrent movement of all six pore loops, which coordinately grip and apply force to the substrate.
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30
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Grison CM, Robin S, Aitken DJ. The discovery of 9/8-ribbons, β/γ-peptides with curved shapes governed by a combined configuration-conformation code. Chem Commun (Camb) 2015; 51:16233-6. [DOI: 10.1039/c5cc07136d] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
The design of a β/γ-peptide reveals an unprecedented 9/8-ribbon whose curvature depends on the β-residue configuration and the γ-residue conformation.
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Affiliation(s)
- Claire M. Grison
- CP3A Organic Synthesis Group
- ICMMO-UMR 8182
- Université Paris-Sud
- Université Paris-Saclay
- 91405 Orsay cedex
| | - Sylvie Robin
- CP3A Organic Synthesis Group
- ICMMO-UMR 8182
- Université Paris-Sud
- Université Paris-Saclay
- 91405 Orsay cedex
| | - David J. Aitken
- CP3A Organic Synthesis Group
- ICMMO-UMR 8182
- Université Paris-Sud
- Université Paris-Saclay
- 91405 Orsay cedex
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31
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Liu S, Chistol G, Bustamante C. Mechanical operation and intersubunit coordination of ring-shaped molecular motors: insights from single-molecule studies. Biophys J 2014; 106:1844-58. [PMID: 24806916 DOI: 10.1016/j.bpj.2014.03.029] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2014] [Accepted: 03/19/2014] [Indexed: 01/27/2023] Open
Abstract
Ring NTPases represent a large and diverse group of proteins that couple their nucleotide hydrolysis activity to a mechanical task involving force generation and some type of transport process in the cell. Because of their shape, these enzymes often operate as gates that separate distinct cellular compartments to control and regulate the passage of chemical species across them. In this manner, ions and small molecules are moved across membranes, biopolymer substrates are segregated between cells or moved into confined spaces, double-stranded nucleic acids are separated into single strands to provide access to the genetic information, and polypeptides are unfolded and processed for recycling. Here we review the recent advances in the characterization of these motors using single-molecule manipulation and detection approaches. We describe the various mechanisms by which ring motors convert chemical energy to mechanical force or torque and coordinate the activities of individual subunits that constitute the ring. We also examine how single-molecule studies have contributed to a better understanding of the structural elements involved in motor-substrate interaction, mechanochemical coupling, and intersubunit coordination. Finally, we discuss how these molecular motors tailor their operation-often through regulation by other cofactors-to suit their unique biological functions.
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Affiliation(s)
- Shixin Liu
- Jason L. Choy Laboratory of Single-Molecule Biophysics, University of California, Berkeley, and Lawrence Berkeley National Laboratory, Berkeley, California; California Institute for Quantitative Biosciences, University of California, Berkeley, and Lawrence Berkeley National Laboratory, Berkeley, California
| | - Gheorghe Chistol
- Jason L. Choy Laboratory of Single-Molecule Biophysics, University of California, Berkeley, and Lawrence Berkeley National Laboratory, Berkeley, California; Department of Physics, University of California, Berkeley, and Lawrence Berkeley National Laboratory, Berkeley, California
| | - Carlos Bustamante
- Jason L. Choy Laboratory of Single-Molecule Biophysics, University of California, Berkeley, and Lawrence Berkeley National Laboratory, Berkeley, California; California Institute for Quantitative Biosciences, University of California, Berkeley, and Lawrence Berkeley National Laboratory, Berkeley, California; Department of Physics, University of California, Berkeley, and Lawrence Berkeley National Laboratory, Berkeley, California; Department of Molecular and Cell Biology, Department of Chemistry, Howard Hughes Medical Institute, and Kavli Energy NanoSciences Institute, University of California, Berkeley, and Lawrence Berkeley National Laboratory, Berkeley, California.
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32
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Bauer BW, Shemesh T, Chen Y, Rapoport TA. A "push and slide" mechanism allows sequence-insensitive translocation of secretory proteins by the SecA ATPase. Cell 2014; 157:1416-1429. [PMID: 24906156 DOI: 10.1016/j.cell.2014.03.063] [Citation(s) in RCA: 79] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2013] [Revised: 02/22/2014] [Accepted: 03/31/2014] [Indexed: 11/16/2022]
Abstract
In bacteria, most secretory proteins are translocated across the plasma membrane by the interplay of the SecA ATPase and the SecY channel. How SecA moves a broad range of polypeptide substrates is only poorly understood. Here we show that SecA moves polypeptides through the SecY channel by a "push and slide" mechanism. In its ATP-bound state, SecA interacts through a two-helix finger with a subset of amino acids in a substrate, pushing them into the channel. A polypeptide can also passively slide back and forth when SecA is in the predominant ADP-bound state or when SecA encounters a poorly interacting amino acid in its ATP-bound state. SecA performs multiple rounds of ATP hydrolysis before dissociating from SecY. The proposed push and slide mechanism is supported by a mathematical model and explains how SecA allows translocation of a wide range of polypeptides. This mechanism may also apply to hexameric polypeptide-translocating ATPases.
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Affiliation(s)
- Benedikt W Bauer
- Howard Hughes Medical Institute, Harvard Medical School, 240 Longwood Avenue, Boston, MA 02115, USA; Department of Cell Biology, Harvard Medical School, 240 Longwood Avenue, Boston, MA 02115, USA
| | - Tom Shemesh
- Howard Hughes Medical Institute, Harvard Medical School, 240 Longwood Avenue, Boston, MA 02115, USA; Department of Cell Biology, Harvard Medical School, 240 Longwood Avenue, Boston, MA 02115, USA
| | - Yu Chen
- Howard Hughes Medical Institute, Harvard Medical School, 240 Longwood Avenue, Boston, MA 02115, USA; Department of Cell Biology, Harvard Medical School, 240 Longwood Avenue, Boston, MA 02115, USA
| | - Tom A Rapoport
- Howard Hughes Medical Institute, Harvard Medical School, 240 Longwood Avenue, Boston, MA 02115, USA; Department of Cell Biology, Harvard Medical School, 240 Longwood Avenue, Boston, MA 02115, USA.
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33
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Yu J. Coordination and control inside simple biomolecular machines. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2014; 805:353-84. [PMID: 24446369 DOI: 10.1007/978-3-319-02970-2_15] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
Biomolecular machines can achieve physiological functions precisely and efficiently, though they always operate under fluctuations and noises. We review two types of simple machinery that we have recently studied. The machinery can be regarded as molecular motors. They transform chemical free energy from NTP hydrolysis to mechanical work. One type belongs to small monomeric helicases that move directionally along single-stranded nucleic acid, and may further unwind the duplex part for gene replication or repair. The other type belongs to ring-shaped NTPase motors that also move or transport nucleic acid or protein substrate in a directional manner, such as for genome packaging or protein degradation. The central issue in this review is on how the machinery coordinates essential degrees of freedom during the mechanochemical coupling process. Further concerns include how the coordination and control are manifested in experiments, and how they can be captured well in modeling and computational research. We employed atomistic molecular dynamics simulations, coarse-grained analyses, and stochastic modeling techniques to examine the molecular machines at multiple resolutions and timescales. Detailed descriptions on how the protein interacts with its substrate at interface, as well as how multiple protein subunits are coordinated are summarized.
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Affiliation(s)
- Jin Yu
- Beijing Computational Science Research Center, No 3 Heqing Road, Haidian District, Beijing, 100084, China,
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34
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Nyquist K, Martin A. Marching to the beat of the ring: polypeptide translocation by AAA+ proteases. Trends Biochem Sci 2013; 39:53-60. [PMID: 24316303 DOI: 10.1016/j.tibs.2013.11.003] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2013] [Revised: 11/07/2013] [Accepted: 11/12/2013] [Indexed: 11/28/2022]
Abstract
ATP-dependent proteases exist in all cells and are crucial regulators of the proteome. These machines consist of a hexameric, ring-shaped motor responsible for engaging, unfolding, and translocating protein substrates into an associated peptidase for degradation. Here, we discuss recent work that has established how the six motor subunits coordinate their ATP-hydrolysis and translocation activities. The closed topology of the ring and the rigidity of subunit/subunit interfaces cause conformational changes within a single subunit to drive motions in other subunits of the hexamer. This structural effect generates allostery between the ATP-binding sites, leading to a preferred order of binding and hydrolysis events among the motor subunits as well as a unique biphasic mechanism of translocation.
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Affiliation(s)
- Kristofor Nyquist
- QB3 Institute, University of California, Berkeley, CA 94720, USA; Biophysics Graduate Group, University of California, Berkeley, CA 94720, USA
| | - Andreas Martin
- QB3 Institute, University of California, Berkeley, CA 94720, USA; Department of Molecular and Cell Biology, University of California, Berkeley, CA 94720, USA.
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35
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Sauer RT. Mutagenic dissection of the sequence determinants of protein folding, recognition, and machine function. Protein Sci 2013; 22:1675-87. [PMID: 23963737 DOI: 10.1002/pro.2334] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2013] [Accepted: 08/12/2013] [Indexed: 11/08/2022]
Abstract
Understanding the relationship between the amino-acid sequence of a protein and its ability to fold and to function is one of the major challenges of protein science. Here, cases are reviewed in which mutagenesis, biochemistry, structure determination, protein engineering, and single-molecule biophysics have illuminated the sequence determinants of folding, binding specificity, and biological function for DNA-binding proteins and ATP-fueled machines that forcibly unfold native proteins as a prelude to degradation. In addition to structure-function relationships, these studies provide information about folding intermediates, mutations that accelerate folding, slow unfolding, and stabilize proteins against denaturation, show how new binding specificities and folds can evolve, and reveal strategies that proteolytic machines use to recognize, unfold, and degrade thousands of distinct substrates.
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Affiliation(s)
- Robert T Sauer
- Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts, 02139
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36
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Too PHM, Erales J, Simen JD, Marjanovic A, Coffino P. Slippery substrates impair function of a bacterial protease ATPase by unbalancing translocation versus exit. J Biol Chem 2013; 288:13243-57. [PMID: 23530043 DOI: 10.1074/jbc.m113.452524] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
BACKGROUND ATP-dependent proteases translocate and unfold their substrates. RESULTS A human virus sequence with only Gly and Ala residues causes similar dysfunctions of eukaryotic and prokaryotic protease motors: unfolding failure. CONCLUSION Sequences with amino acids of simple shape and small size impair unfolding of contiguous stable domains. SIGNIFICANCE Compartmented ATP-dependent proteases of diverse origin share conserved principles of interaction between translocase/effector and substrate/recipient. ATP-dependent proteases engage, translocate, and unfold substrate proteins. A sequence with only Gly and Ala residues (glycine-alanine repeat; GAr) encoded by the Epstein-Barr virus of humans inhibits eukaryotic proteasome activity. It causes the ATPase translocase to slip on its protein track, stalling unfolding and interrupting degradation. The bacterial protease ClpXP is structurally simpler than the proteasome but has related elements: a regulatory ATPase complex (ClpX) and associated proteolytic chamber (ClpP). In this study, GAr sequences were found to impair ClpXP function much as in proteasomes. Stalling depended on interaction between a GAr and a suitably spaced and positioned folded domain resistant to mechanical unfolding. Persistent unfolding failure results in the interruption of degradation and the production of partial degradation products that include the resistant domain. The capacity of various sequences to cause unfolding failure was investigated. Among those tested, a GAr was most effective, implying that viral selection had optimized processivity failure. More generally, amino acids of simple shape and small size promoted unfolding failure. The ClpX ATPase is a homohexamer. Partial degradation products could exit the complex through transient gaps between the ClpX monomers or, alternatively, by backing out. Production of intermediates by diverse topological forms of the hexamer was shown to be similar, excluding lateral escape. In principle, a GAr could interrupt degradation because 1) the translocase thrusts forward less effectively or because 2) the translocase retains substrate less well when resetting between forward strokes. Kinetic analysis showed that the predominant effect was through the second of these mechanisms.
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Affiliation(s)
- Priscilla Hiu-Mei Too
- Department of Microbiology and Immunology, University of California, San Francisco, California 94143, USA
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37
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Abstract
Bacteria are frequently exposed to changes in environmental conditions, such as fluctuations in temperature, pH or the availability of nutrients. These assaults can be detrimental to cell as they often result in a proteotoxic stress, which can cause the accumulation of unfolded proteins. In order to restore a productive folding environment in the cell, bacteria have evolved a network of proteins, known as the protein quality control (PQC) network, which is composed of both chaperones and AAA+ proteases. These AAA+ proteases form a major part of this PQC network, as they are responsible for the removal of unwanted and damaged proteins. They also play an important role in the turnover of specific regulatory or tagged proteins. In this review, we describe the general features of an AAA+ protease, and using two of the best-characterised AAA+ proteases in Escherichia coli (ClpAP and ClpXP) as a model for all AAA+ proteases, we provide a detailed mechanistic description of how these machines work. Specifically, the review examines the physiological role of these machines, as well as the substrates and the adaptor proteins that modulate their substrate specificity.
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38
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Gestwicki JE, Garza D. Protein quality control in neurodegenerative disease. PROGRESS IN MOLECULAR BIOLOGY AND TRANSLATIONAL SCIENCE 2012; 107:327-53. [PMID: 22482455 DOI: 10.1016/b978-0-12-385883-2.00003-5] [Citation(s) in RCA: 58] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
The accumulation of misfolded proteins is a common feature of many neurodegenerative diseases. These observations suggest a potential link between these disorders and protein quality control, a collection of cellular pathways that sense damage to proteins and facilitate their turnover. Consistent with this idea, activation of quality control components, such as molecular chaperones, has been shown to be protective in multiple neurodegenerative disease models. In addition, key studies have suggested that quality control deteriorates with age, further supporting a relationship between these processes. In this chapter, we discuss the evidence linking neurodegeneration to quality control and present the emerging models. We also speculate on why proper quality control is so difficult for certain proteins.
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Affiliation(s)
- Jason E Gestwicki
- Department of Pathology and the Life Sciences Institute, University of Michigan, Ann Arbor, Michigan, USA
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39
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Davis JH, Baker TA, Sauer RT. Small-molecule control of protein degradation using split adaptors. ACS Chem Biol 2011; 6:1205-13. [PMID: 21866931 DOI: 10.1021/cb2001389] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Targeted intracellular degradation provides a method to study the biological function of proteins and has numerous applications in biotechnology. One promising approach uses adaptor proteins to target substrates with genetically encoded degradation tags for proteolysis. Here, we describe an engineered split-adaptor system, in which adaptor assembly and delivery of substrates to the ClpXP protease depends on a small molecule (rapamycin). This degradation system does not require modification of endogenous proteases, functions robustly over a wide range of adaptor concentrations, and does not require new synthesis of adaptors or proteases to initiate degradation. We demonstrate the efficacy of this system in E. coli by degrading tagged variants of LacI repressor and FtsA, an essential cell-division protein. In the latter case, addition of rapamycin causes pronounced filamentation because daughter cells cannot divide. Strikingly, washing rapamycin away reverses this phenotype. Our system is highly modular, with clearly defined interfaces for substrate binding, protease binding, and adaptor assembly, providing a clear path to extend this system to other degradation tags, proteases, or induction systems. Together, these new reagents should be useful in controlling protein degradation in bacteria.
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Affiliation(s)
- Joseph H. Davis
- Department of Biology and ‡Howard Hughes Medical Institute, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
| | - Tania A. Baker
- Department of Biology and ‡Howard Hughes Medical Institute, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
| | - Robert T. Sauer
- Department of Biology and ‡Howard Hughes Medical Institute, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
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40
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Venkatesh S, Lee J, Singh K, Lee I, Suzuki CK. Multitasking in the mitochondrion by the ATP-dependent Lon protease. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2011; 1823:56-66. [PMID: 22119779 DOI: 10.1016/j.bbamcr.2011.11.003] [Citation(s) in RCA: 119] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/02/2011] [Revised: 10/30/2011] [Accepted: 11/06/2011] [Indexed: 01/13/2023]
Abstract
The AAA(+) Lon protease is a soluble single-ringed homo-oligomer, which represents the most streamlined operational unit mediating ATP-dependent proteolysis. Despite its simplicity, the architecture of Lon proteases exhibits a species-specific diversity. Homology modeling provides insights into the structural features that distinguish bacterial and human Lon proteases as hexameric complexes from yeast Lon, which is uniquely heptameric. The best-understood functions of mitochondrial Lon are linked to maintaining proteostasis under normal metabolic conditions, and preventing proteotoxicity during environmental and cellular stress. An intriguing property of human Lon is its specific binding to G-quadruplex DNA, and its association with the mitochondrial genome in cultured cells. A fraction of Lon preferentially binds to the control region of mitochondrial DNA where transcription and replication are initiated. Here, we present an overview of the diverse functions of mitochondrial Lon, as well as speculative perspectives on its role in protein and mtDNA quality control.
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Affiliation(s)
- Sundararajan Venkatesh
- Department of Biochemistry and Molecular Biology, University of Medicine and Dentistry of New Jersey, New Jersey Medical School, 185 South Orange Avenue, MSB E-633, Newark, New Jersey 07103 USA
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41
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Gur E, Biran D, Ron EZ. Regulated proteolysis in Gram-negative bacteria--how and when? Nat Rev Microbiol 2011; 9:839-48. [PMID: 22020261 DOI: 10.1038/nrmicro2669] [Citation(s) in RCA: 105] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Most bacteria live in a dynamic environment where temperature, availability of nutrients and the presence of various chemicals vary, which requires rapid adaptation. Many of the adaptive changes are determined by changes in the transcription of global regulatory networks, but this response is slow because most bacterial proteins are stable and their concentration remains high even after transcription slows down. To respond rapidly, an additional level of regulation has evolved: the degradation of key proteins. However, as proteolysis is an irreversible process, it is subject to tight regulation of substrate binding and degradation. Here we review the roles of the proteolytic enzymes in Gram-negative bacteria and how these enzymes can be regulated to target only a subset of proteins.
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Affiliation(s)
- Eyal Gur
- Department of Life Sciences, Ben-Gurion University of the Negev, Beer Sheva, Israel
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42
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Abstract
AAA+ family proteolytic machines (ClpXP, ClpAP, ClpCP, HslUV, Lon, FtsH, PAN/20S, and the 26S proteasome) perform protein quality control and are used in regulatory circuits in all cells. These machines contain a compartmental protease, with active sites sequestered in an interior chamber, and a hexameric ring of AAA+ ATPases. Substrate proteins are tethered to the ring, either directly or via adaptor proteins. An unstructured region of the substrate is engaged in the axial pore of the AAA+ ring, and cycles of ATP binding/hydrolysis drive conformational changes that create pulses of pulling that denature the substrate and translocate the unfolded polypeptide through the pore and into the degradation chamber. Here, we review our current understanding of the molecular mechanisms of substrate recognition, adaptor function, and ATP-fueled unfolding and translocation. The unfolding activities of these and related AAA+ machines can also be used to disassemble or remodel macromolecular complexes and to resolubilize aggregates.
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Affiliation(s)
- Robert T Sauer
- Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139
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43
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Maillard RA, Chistol G, Sen M, Righini M, Tan J, Kaiser CM, Hodges C, Martin A, Bustamante C. ClpX(P) generates mechanical force to unfold and translocate its protein substrates. Cell 2011; 145:459-69. [PMID: 21529717 DOI: 10.1016/j.cell.2011.04.010] [Citation(s) in RCA: 228] [Impact Index Per Article: 17.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2011] [Revised: 03/29/2011] [Accepted: 04/14/2011] [Indexed: 11/17/2022]
Abstract
AAA(+) unfoldases denature and translocate polypeptides into associated peptidases. We report direct observations of mechanical, force-induced protein unfolding by the ClpX unfoldase from E. coli, alone, and in complex with the ClpP peptidase. ClpX hydrolyzes ATP to generate mechanical force and translocate polypeptides through its central pore. Threading is interrupted by pauses that are found to be off the main translocation pathway. ClpX's translocation velocity is force dependent, reaching a maximum of 80 aa/s near-zero force and vanishing at around 20 pN. ClpX takes 1, 2, or 3 nm steps, suggesting a fundamental step-size of 1 nm and a certain degree of intersubunit coordination. When ClpX encounters a folded protein, it either overcomes this mechanical barrier or slips on the polypeptide before making another unfolding attempt. Binding of ClpP decreases the slip probability and enhances the unfolding efficiency of ClpX. Under the action of ClpXP, GFP unravels cooperatively via a transient intermediate.
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Affiliation(s)
- Rodrigo A Maillard
- Jason L. Choy Laboratory of Single-Molecule Biophysics, University of California, Berkeley, 94720, USA
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44
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ClpXP, an ATP-powered unfolding and protein-degradation machine. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2011; 1823:15-28. [PMID: 21736903 DOI: 10.1016/j.bbamcr.2011.06.007] [Citation(s) in RCA: 321] [Impact Index Per Article: 24.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/30/2011] [Revised: 06/10/2011] [Accepted: 06/15/2011] [Indexed: 11/23/2022]
Abstract
ClpXP is a AAA+ protease that uses the energy of ATP binding and hydrolysis to perform mechanical work during targeted protein degradation within cells. ClpXP consists of hexamers of a AAA+ ATPase (ClpX) and a tetradecameric peptidase (ClpP). Asymmetric ClpX hexamers bind unstructured peptide tags in protein substrates, unfold stable tertiary structure in the substrate, and then translocate the unfolded polypeptide chain into an internal proteolytic compartment in ClpP. Here, we review our present understanding of ClpXP structure and function, as revealed by two decades of biochemical and biophysical studies.
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45
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Aubin-Tam ME, Olivares AO, Sauer RT, Baker TA, Lang MJ. Single-molecule protein unfolding and translocation by an ATP-fueled proteolytic machine. Cell 2011; 145:257-67. [PMID: 21496645 DOI: 10.1016/j.cell.2011.03.036] [Citation(s) in RCA: 203] [Impact Index Per Article: 15.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2010] [Revised: 03/07/2011] [Accepted: 03/11/2011] [Indexed: 12/30/2022]
Abstract
All cells employ ATP-powered proteases for protein-quality control and regulation. In the ClpXP protease, ClpX is a AAA+ machine that recognizes specific protein substrates, unfolds these molecules, and then translocates the denatured polypeptide through a central pore and into ClpP for degradation. Here, we use optical-trapping nanometry to probe the mechanics of enzymatic unfolding and translocation of single molecules of a multidomain substrate. Our experiments demonstrate the capacity of ClpXP and ClpX to perform mechanical work under load, reveal very fast and highly cooperative unfolding of individual substrate domains, suggest a translocation step size of 5-8 amino acids, and support a power-stroke model of denaturation in which successful enzyme-mediated unfolding of stable domains requires coincidence between mechanical pulling by the enzyme and a transient stochastic reduction in protein stability. We anticipate that single-molecule studies of the mechanical properties of other AAA+ proteolytic machines will reveal many shared features with ClpXP.
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Affiliation(s)
- Marie-Eve Aubin-Tam
- Department of Mechanical Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
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46
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Merrill SA, Hanson PI. Activation of human VPS4A by ESCRT-III proteins reveals ability of substrates to relieve enzyme autoinhibition. J Biol Chem 2010; 285:35428-38. [PMID: 20805225 DOI: 10.1074/jbc.m110.126318] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
VPS4 proteins are AAA(+) ATPases required to form multivesicular bodies, release viral particles, and complete cytokinesis. They act by disassembling ESCRT-III heteropolymers during or after their proposed function in membrane scission. Here we show that purified human VPS4A is essentially inactive but can be stimulated to hydrolyze ATP by ESCRT-III proteins in a reaction that requires both their previously defined MIT interacting motifs and ∼50 amino acids of the adjacent sequence. Importantly, C-terminal fragments of all ESCRT-III proteins tested, including CHMP2A, CHMP1B, CHMP3, CHMP4A, CHMP6, and CHMP5, activated VPS4A suggesting that it disassembles ESCRT-III heteropolymers by affecting each component protein. VPS4A is thought to act as a ring-shaped cylindrical oligomer like other AAA(+) ATPases, but this has been difficult to directly demonstrate. We found that concentrating His(6)-VPS4A on liposomes containing Ni(2+)-nitrilotriacetic acid-tagged lipid increased ATP hydrolysis, confirming the importance of inter-subunit interactions for activity. We also found that mutating pore loops expected to line the center of a cylindrical oligomer changed the response of VPS4A to ESCRT-III proteins. Based on these data, we propose that ESCRT-III proteins facilitate assembly of functional but transient VPS4A oligomers and interact with sequences inside the pore of the assembled enzyme. Deleting the N-terminal MIT domain and adjacent linker from VPS4A increased both basal and liposome-enhanced ATPase activity, indicating that these elements play a role in autoinhibiting VPS4A until it encounters ESCRT-III proteins. These findings reveal new ways in which VPS4 activity is regulated and specifically directed to ESCRT-III polymers.
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Affiliation(s)
- Samuel A Merrill
- Department of Cell Biology and Physiology, Washington University School of Medicine, St Louis, Missouri 63110, USA
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47
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Membrane budding and scission by the ESCRT machinery: it's all in the neck. Nat Rev Mol Cell Biol 2010; 11:556-66. [PMID: 20588296 DOI: 10.1038/nrm2937] [Citation(s) in RCA: 545] [Impact Index Per Article: 38.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
The endosomal sorting complexes required for transport (ESCRTs) catalyse one of the most unusual membrane remodelling events in cell biology. ESCRT-I and ESCRT-II direct membrane budding away from the cytosol by stabilizing bud necks without coating the buds and without being consumed in the buds. ESCRT-III cleaves the bud necks from their cytosolic faces. ESCRT-III-mediated membrane neck cleavage is crucial for many processes, including the biogenesis of multivesicular bodies, viral budding, cytokinesis and, probably, autophagy. Recent studies of ultrastructures induced by ESCRT-III overexpression in cells and the in vitro reconstitution of the budding and scission reactions have led to breakthroughs in understanding these remarkable membrane reactions.
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48
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Jaru-Ampornpan P, Shen K, Lam VQ, Ali M, Doniach S, Jia TZ, Shan SO. ATP-independent reversal of a membrane protein aggregate by a chloroplast SRP subunit. Nat Struct Mol Biol 2010; 17:696-702. [PMID: 20424608 PMCID: PMC2917185 DOI: 10.1038/nsmb.1836] [Citation(s) in RCA: 56] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2010] [Accepted: 04/20/2010] [Indexed: 02/06/2023]
Abstract
Membrane proteins impose enormous challenges to cellular protein homeostasis during their post-translational targeting, and they require chaperones to keep them soluble and translocation competent. Here we show that a novel targeting factor in the chloroplast signal recognition particle (cpSRP), cpSRP43, is a highly specific molecular chaperone that efficiently reverses the aggregation of its substrate proteins. In contrast to 'ATPases associated with various cellular activities' (AAA(+)) chaperones, cpSRP43 uses specific binding interactions with its substrate to mediate its 'disaggregase' activity. This disaggregase capability can allow targeting machineries to more effectively capture their protein substrates and emphasizes a close connection between protein folding and trafficking processes. Moreover, cpSRP43 provides the first example to our knowledge of an ATP-independent disaggregase and shows that efficient reversal of protein aggregation can be attained by specific binding interactions between a chaperone and its substrate.
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Affiliation(s)
- Peera Jaru-Ampornpan
- Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California, USA
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49
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Lee ME, Baker TA, Sauer RT. Control of substrate gating and translocation into ClpP by channel residues and ClpX binding. J Mol Biol 2010; 399:707-18. [PMID: 20416323 DOI: 10.1016/j.jmb.2010.04.027] [Citation(s) in RCA: 63] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2010] [Revised: 04/12/2010] [Accepted: 04/15/2010] [Indexed: 11/25/2022]
Abstract
ClpP is a self-compartmentalized protease, which has very limited degradation activity unless it associates with ClpX to form ClpXP or with ClpA to form ClpAP. Here, we show that ClpX binding stimulates ClpP cleavage of peptides larger than a few amino acids and enhances ClpP active-site modification. Stimulation requires ATP binding but not hydrolysis by ClpX. The magnitude of this enhancement correlates with increasing molecular weight of the molecule entering ClpP. Amino-acid substitutions in the channel loop or helix A of ClpP enhance entry of larger substrates into the free enzyme, eliminate ClpX binding in some cases, and are not further stimulated by ClpX binding in other instances. These results support a model in which the channel residues of free ClpP exclude efficient entry of all but the smallest peptides into the degradation chamber, with ClpX binding serving to relieve these inhibitory interactions. Specific ClpP channel variants also prevent ClpXP translocation of certain amino-acid sequences, suggesting that the wild-type channel plays an important role in facilitating broad translocation specificity. In combination with previous studies, our results indicate that collaboration between ClpP and its partner ATPases opens a gate that functions to exclude larger substrates from isolated ClpP.
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Affiliation(s)
- Mary E Lee
- Department of Biology, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
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50
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Glynn SE, Martin A, Nager AR, Baker TA, Sauer RT. Structures of asymmetric ClpX hexamers reveal nucleotide-dependent motions in a AAA+ protein-unfolding machine. Cell 2009; 139:744-56. [PMID: 19914167 DOI: 10.1016/j.cell.2009.09.034] [Citation(s) in RCA: 216] [Impact Index Per Article: 14.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2009] [Revised: 06/21/2009] [Accepted: 09/09/2009] [Indexed: 11/18/2022]
Abstract
ClpX is a AAA+ machine that uses the energy of ATP binding and hydrolysis to unfold native proteins and translocate unfolded polypeptides into the ClpP peptidase. The crystal structures presented here reveal striking asymmetry in ring hexamers of nucleotide-free and nucleotide-bound ClpX. Asymmetry arises from large changes in rotation between the large and small AAA+ domains of individual subunits. These differences prevent nucleotide binding to two subunits, generate a staggered arrangement of ClpX subunits and pore loops around the hexameric ring, and provide a mechanism for coupling conformational changes caused by ATP binding or hydrolysis in one subunit to flexing motions of the entire ring. Our structures explain numerous solution studies of ClpX function, predict mechanisms for pore elasticity during translocation of irregular polypeptides, and suggest how repetitive conformational changes might be coupled to mechanical work during the ATPase cycle of ClpX and related molecular machines.
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Affiliation(s)
- Steven E Glynn
- Department of Biology, Howard Hughes Medical Institute, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
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