1
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Lewis K, Lee RE, Brötz-Oesterhelt H, Hiller S, Rodnina MV, Schneider T, Weingarth M, Wohlgemuth I. Sophisticated natural products as antibiotics. Nature 2024; 632:39-49. [PMID: 39085542 DOI: 10.1038/s41586-024-07530-w] [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: 12/28/2022] [Accepted: 05/07/2024] [Indexed: 08/02/2024]
Abstract
In this Review, we explore natural product antibiotics that do more than simply inhibit an active site of an essential enzyme. We review these compounds to provide inspiration for the design of much-needed new antibacterial agents, and examine the complex mechanisms that have evolved to effectively target bacteria, including covalent binders, inhibitors of resistance, compounds that utilize self-promoted entry, those that evade resistance, prodrugs, target corrupters, inhibitors of 'undruggable' targets, compounds that form supramolecular complexes, and selective membrane-acting agents. These are exemplified by β-lactams that bind covalently to inhibit transpeptidases and β-lactamases, siderophore chimeras that hijack import mechanisms to smuggle antibiotics into the cell, compounds that are activated by bacterial enzymes to produce reactive molecules, and antibiotics such as aminoglycosides that corrupt, rather than merely inhibit, their targets. Some of these mechanisms are highly sophisticated, such as the preformed β-strands of darobactins that target the undruggable β-barrel chaperone BamA, or teixobactin, which binds to a precursor of peptidoglycan and then forms a supramolecular structure that damages the membrane, impeding the emergence of resistance. Many of the compounds exhibit more than one notable feature, such as resistance evasion and target corruption. Understanding the surprising complexity of the best antimicrobial compounds provides a roadmap for developing novel compounds to address the antimicrobial resistance crisis by mining for new natural products and inspiring us to design similarly sophisticated antibiotics.
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Affiliation(s)
- Kim Lewis
- Antimicrobial Discovery Center, Northeastern University, Boston, MA, USA.
| | - Richard E Lee
- Department of Chemical Biology and Therapeutics, St Jude Children's Research Hospital, Memphis, TN, USA.
| | - Heike Brötz-Oesterhelt
- Interfaculty Institute of Microbiology and Infection Medicine, Tubingen, Germany
- Controlling Microbes to Fight Infection-Cluster of Excellence, Tubingen, Germany
| | | | - Marina V Rodnina
- Max Planck Institute for Multidisciplinary Sciences, Goettingen, Germany
| | - Tanja Schneider
- Institute for Pharmaceutical Microbiology, University of Bonn, University Hospital Bonn, Bonn, Germany
- German Center for Infection Research (DZIF), Partner Site Cologne-Bonn, Bonn, Germany
| | - Markus Weingarth
- Chemistry Department, Utrecht University, Utrecht, the Netherlands
| | - Ingo Wohlgemuth
- Max Planck Institute for Multidisciplinary Sciences, Goettingen, Germany
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2
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Mindrebo JT, Lander GC. Structural and mechanistic studies on human LONP1 redefine the hand-over-hand translocation mechanism. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.06.24.600538. [PMID: 38979310 PMCID: PMC11230189 DOI: 10.1101/2024.06.24.600538] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/10/2024]
Abstract
AAA+ enzymes use energy from ATP hydrolysis to remodel diverse cellular targets. Structures of substrate-bound AAA+ complexes suggest that these enzymes employ a conserved hand-over-hand mechanism to thread substrates through their central pore. However, the fundamental aspects of the mechanisms governing motor function and substrate processing within specific AAA+ families remain unresolved. We used cryo-electron microscopy to structurally interrogate reaction intermediates from in vitro biochemical assays to inform the underlying regulatory mechanisms of the human mitochondrial AAA+ protease, LONP1. Our results demonstrate that substrate binding allosterically regulates proteolytic activity, and that LONP1 can adopt a configuration conducive to substrate translocation even when the ATPases are bound to ADP. These results challenge the conventional understanding of the hand-over-hand translocation mechanism, giving rise to an alternative model that aligns more closely with biochemical and biophysical data on related enzymes like ClpX, ClpA, the 26S proteasome, and Lon protease.
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Affiliation(s)
- Jeffrey T. Mindrebo
- Department of Integrative Structural and Computational Biology, Scripps Research; La Jolla, CA, USA
| | - Gabriel C. Lander
- Department of Integrative Structural and Computational Biology, Scripps Research; La Jolla, CA, USA
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3
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Beardslee PC, Schmitz KR. Toxin-based screening of C-terminal tags in Escherichia coli reveals the exceptional potency of ssrA-like degrons. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.01.29.576913. [PMID: 38352471 PMCID: PMC10862746 DOI: 10.1101/2024.01.29.576913] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 02/22/2024]
Abstract
All bacteria possess ATP-dependent proteases that destroy cytosolic proteins. These enzymes help cells mitigate proteotoxic stress, adapt to changing nutrient availability, regulate virulence phenotypes, and transition to pathogenic lifestyles. Moreover, ATP-dependent proteases have emerged as promising antibacterial and antivirulence targets in a variety of pathogens. The physiological roles of these proteases are largely defined by the complement of proteins that they degrade. Substrates are typically recognized in a highly selective manner, often via short unstructured sequences termed degrons. While a few degrons have been identified and rigorously characterized, we lack a systematic understanding of how proteases select valid degrons from the vast complexity of protein sequence space. Here, we describe a novel high-throughput screening approach in Escherichia coli that couples proteolysis of a protein toxin to cell survival. We used this method to screen a combinatorial library of C-terminal pentapeptide sequences for functionality as proteolytic degrons in wild type E. coli, and in strains lacking components of the ClpXP and ClpAP proteases. By examining the competitive enrichment of sequences over time, we found that about one percent of pentapeptide tags lead to toxin proteolysis. Interestingly, the most enriched degrons were ClpXP-dependent and highly similar to the ssrA tag, one of the most extensively characterized degrons in bacteria. Among ssrA-like sequences, we observed that specific upstream residues correlate with successful recognition. The lack of diversity among strongly enriched sequences suggests that ssrA-like tags comprise a uniquely potent class of short C-terminal degron in E. coli. Efficient proteolysis of substrates lacking such degrons likely requires adaptors or multivalent interactions. These findings broaden our understanding of the constraints that shape the bacterial proteolytic landscape. Our screening approach may be broadly applicable to probing aspects of proteolytic substrate selection in other bacterial systems.
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Affiliation(s)
- Patrick C. Beardslee
- Department of Chemistry & Biochemistry, University of Delaware, Newark DE, 19716
| | - Karl R. Schmitz
- Department of Chemistry & Biochemistry, University of Delaware, Newark DE, 19716
- Department of Biological Sciences, University of Delaware, Newark DE, 19716
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4
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Kasal MR, Kotamarthi HC, Johnson MM, Stephens HM, Lang MJ, Sauer RT, Baker TA. Lon degrades stable substrates slowly but with enhanced processivity, redefining the attributes of a successful AAA+ protease. Cell Rep 2023; 42:113061. [PMID: 37660294 PMCID: PMC10695633 DOI: 10.1016/j.celrep.2023.113061] [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: 03/02/2023] [Revised: 07/15/2023] [Accepted: 08/16/2023] [Indexed: 09/05/2023] Open
Abstract
Lon is a widely distributed AAA+ (ATPases associated with diverse cellular activities) protease known for degrading poorly folded and damaged proteins and is often classified as a weak protein unfoldase. Here, using a Lon-degron pair from Mesoplasma florum (MfLon and MfssrA, respectively), we perform ensemble and single-molecule experiments to elucidate the molecular mechanisms underpinning MfLon function. Notably, we find that MfLon unfolds and degrades stably folded substrates and that translocation of these unfolded polypeptides occurs with a ∼6-amino-acid step size. Moreover, the time required to hydrolyze one ATP corresponds to the dwell time between steps, indicating that one step occurs per ATP-hydrolysis-fueled "power stroke." Comparison of MfLon to related AAA+ enzymes now provides strong evidence that HCLR-clade enzymes function using a shared power-stroke mechanism and, surprisingly, that MfLon is more processive than ClpXP and ClpAP. We propose that ample unfoldase strength and substantial processivity are features that contribute to the Lon family's evolutionary success.
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Affiliation(s)
- Meghann R Kasal
- Department of Biology, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
| | | | - Madeline M Johnson
- Department of Chemical and Biomolecular Engineering, Vanderbilt University, Nashville, TN 37235, USA
| | - Hannah M Stephens
- Department of Chemical and Biomolecular Engineering, Vanderbilt University, Nashville, TN 37235, USA
| | - Matthew J Lang
- Department of Chemical and Biomolecular Engineering, Vanderbilt University, Nashville, TN 37235, USA
| | - Robert T Sauer
- 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.
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5
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Mukherjee S, Mepperi J, Sahu P, Barman DK, Kotamarthi HC. Single-Molecule Optical Tweezers As a Tool for Delineating the Mechanisms of Protein-Processing Mechanoenzymes. ACS OMEGA 2023; 8:87-97. [PMID: 36643560 PMCID: PMC9835622 DOI: 10.1021/acsomega.2c06044] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/19/2022] [Accepted: 12/06/2022] [Indexed: 06/17/2023]
Abstract
Mechanoenzymes convert chemical energy from the hydrolysis of nucleotide triphosphates to mechanical energy for carrying out cellular functions ranging from DNA unwinding to protein degradation. Protein-processing mechanoenzymes either remodel the protein structures or translocate them across cellular compartments in an energy-dependent manner. Optical-tweezer-based single-molecule force spectroscopy assays have divulged information on details of chemo-mechanical coupling, directed motion, as well as mechanical forces these enzymes are capable of generating. In this review, we introduce the working principles of optical tweezers as a single-molecule force spectroscopy tool and assays developed to decipher the properties such as unfolding kinetics, translocation velocities, and step sizes by protein remodeling mechanoenzymes. We focus on molecular motors involved in protein degradation and disaggregation, i.e., ClpXP, ClpAP, and ClpB, and insights provided by single-molecule assays on kinetics and stepping dynamics during protein unfolding and translocation. Cellular activities such as protein synthesis, folding, and translocation across membranes are also energy dependent, and the recent single-molecule studies decoding the role of mechanical forces on these processes have been discussed.
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6
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Walker SD, Olivares AO. The activated ClpP peptidase forcefully grips a protein substrate. Biophys J 2022; 121:3907-3916. [PMID: 36045571 PMCID: PMC9674977 DOI: 10.1016/j.bpj.2022.08.042] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2022] [Revised: 08/12/2022] [Accepted: 08/26/2022] [Indexed: 11/26/2022] Open
Abstract
ATPases associated with diverse cellular activities (AAA+) proteases power the maintenance of protein homeostasis by coupling ATP hydrolysis to mechanical protein unfolding, translocation, and ultimately degradation. Although ATPase activity drives a large portion of the mechanical work these molecular machines perform, how the peptidase contributes to the forceful denaturation and processive threading of substrates remains unknown. Here, using single-molecule optical trapping, we examine the mechanical activity of the caseinolytic peptidase P (ClpP) from Escherichia coli in the absence of a partner ATPase and in the presence of an activating small-molecule acyldepsipeptide. We demonstrate that ClpP grips protein substrate under mechanical loads exceeding 40 pN, which are greater than those observed for the AAA+ unfoldase ClpX and the AAA+ protease complexes ClpXP and ClpAP. We further characterize substrate-ClpP bond lifetimes and rupture forces under varying loads. We find that the resulting slip bond behavior does not depend on ClpP peptidase activity. In addition, we find that unloaded bond lifetimes between ClpP and protein substrate are on a timescale relevant to unfolding times (up to ∼160 s) for difficult to unfold model substrate proteins. These direct measurements of the substrate-peptidase bond under load define key properties required by AAA+ proteases to mechanically unfold and degrade protein substrates.
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Affiliation(s)
- Steven D Walker
- Department of Biochemistry, Vanderbilt University, Nashville, Tennessee; Chemical and Physical Biology Graduate Program, Vanderbilt University, Nashville, Tennessee
| | - Adrian O Olivares
- Department of Biochemistry, Vanderbilt University, Nashville, Tennessee.
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7
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Insights into the Structure and Function of the Pex1/Pex6 AAA-ATPase in Peroxisome Homeostasis. Cells 2022; 11:cells11132067. [PMID: 35805150 PMCID: PMC9265785 DOI: 10.3390/cells11132067] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2022] [Revised: 06/25/2022] [Accepted: 06/26/2022] [Indexed: 02/01/2023] Open
Abstract
The AAA-ATPases Pex1 and Pex6 are required for the formation and maintenance of peroxisomes, membrane-bound organelles that harbor enzymes for specialized metabolism. Together, Pex1 and Pex6 form a heterohexameric AAA-ATPase capable of unfolding substrate proteins via processive threading through a central pore. Here, we review the proposed roles for Pex1/Pex6 in peroxisome biogenesis and degradation, discussing how the unfolding of potential substrates contributes to peroxisome homeostasis. We also consider how advances in cryo-EM, computational structure prediction, and mechanisms of related ATPases are improving our understanding of how Pex1/Pex6 converts ATP hydrolysis into mechanical force. Since mutations in PEX1 and PEX6 cause the majority of known cases of peroxisome biogenesis disorders such as Zellweger syndrome, insights into Pex1/Pex6 structure and function are important for understanding peroxisomes in human health and disease.
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8
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Riven I, Mazal H, Iljina M, Haran G. Fast dynamics shape the function of the
AAA
+ machine
ClpB
: lessons from single‐molecule
FRET
spectroscopy. FEBS J 2022. [DOI: 10.1111/febs.16539] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2022] [Revised: 05/04/2022] [Accepted: 05/30/2022] [Indexed: 12/01/2022]
Affiliation(s)
- Inbal Riven
- 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
| | - Marija Iljina
- 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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9
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AAA+ proteins: one motor, multiple ways to work. Biochem Soc Trans 2022; 50:895-906. [PMID: 35356966 DOI: 10.1042/bst20200350] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2021] [Revised: 03/14/2022] [Accepted: 03/15/2022] [Indexed: 12/15/2022]
Abstract
Numerous ATPases associated with diverse cellular activities (AAA+) proteins form hexameric, ring-shaped complexes that function via ATPase-coupled translocation of substrates across the central channel. Cryo-electron microscopy of AAA+ proteins processing substrate has revealed non-symmetric, staircase-like hexameric structures that indicate a sequential clockwise/2-residue step translocation model for these motors. However, for many of the AAA+ proteins that share similar structural features, their translocation properties have not yet been experimentally determined. In the cases where translocation mechanisms have been determined, a two-residue translocation step-size has not been resolved. In this review, we explore Hsp104, ClpB, ClpA and ClpX as examples to review the experimental methods that have been used to examine, in solution, the translocation mechanisms employed by AAA+ motor proteins. We then ask whether AAA+ motors sharing similar structural features can have different translocation mechanisms. Finally, we discuss whether a single AAA+ motor can adopt multiple translocation mechanisms that are responsive to different challenges imposed by the substrate or the environment. We suggest that AAA+ motors adopt more than one translocation mechanism and are tuned to switch to the most energetically efficient mechanism when constraints are applied.
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10
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Division of labor between the pore-1 loops of the D1 and D2 AAA+ rings coordinates substrate selectivity of the ClpAP protease. J Biol Chem 2021; 297:101407. [PMID: 34780718 PMCID: PMC8666677 DOI: 10.1016/j.jbc.2021.101407] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2021] [Revised: 11/06/2021] [Accepted: 11/08/2021] [Indexed: 11/24/2022] Open
Abstract
ClpAP, an ATP-dependent protease consisting of ClpA, a double-ring hexameric unfoldase of the ATPases associated with diverse cellular activities superfamily, and the ClpP peptidase, degrades damaged and unneeded proteins to support cellular proteostasis. ClpA recognizes many protein substrates directly, but it can also be regulated by an adapter, ClpS, that modifies ClpA’s substrate profile toward N-degron substrates. Conserved tyrosines in the 12 pore-1 loops lining the central channel of the stacked D1 and D2 rings of ClpA are critical for degradation, but the roles of these residues in individual steps during direct or adapter-mediated degradation are poorly understood. Using engineered ClpA hexamers with zero, three, or six pore-1 loop mutations in each ATPases associated with diverse cellular activities superfamily ring, we found that active D1 pore loops initiate productive engagement of substrates, whereas active D2 pore loops are most important for mediating the robust unfolding of stable native substrates. In complex with ClpS, active D1 pore loops are required to form a high affinity ClpA•ClpS•substrate complex, but D2 pore loops are needed to “tug on” and remodel ClpS to transfer the N-degron substrate to ClpA. Overall, we find that the pore-1 loop tyrosines in D1 are critical for direct substrate engagement, whereas ClpS-mediated substrate delivery requires unique contributions from both the D1 and D2 pore loops. In conclusion, our study illustrates how pore loop engagement, substrate capture, and powering of the unfolding/translocation steps are distributed between the two rings of ClpA, illuminating new mechanistic features that may be common to double-ring protein unfolding machines.
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11
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Khan YA, White KI, Brunger AT. The AAA+ superfamily: a review of the structural and mechanistic principles of these molecular machines. Crit Rev Biochem Mol Biol 2021; 57:156-187. [PMID: 34632886 DOI: 10.1080/10409238.2021.1979460] [Citation(s) in RCA: 44] [Impact Index Per Article: 14.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
ATPases associated with diverse cellular activities (AAA+ proteins) are a superfamily of proteins found throughout all domains of life. The hallmark of this family is a conserved AAA+ domain responsible for a diverse range of cellular activities. Typically, AAA+ proteins transduce chemical energy from the hydrolysis of ATP into mechanical energy through conformational change, which can drive a variety of biological processes. AAA+ proteins operate in a variety of cellular contexts with diverse functions including disassembly of SNARE proteins, protein quality control, DNA replication, ribosome assembly, and viral replication. This breadth of function illustrates both the importance of AAA+ proteins in health and disease and emphasizes the importance of understanding conserved mechanisms of chemo-mechanical energy transduction. This review is divided into three major portions. First, the core AAA+ fold is presented. Next, the seven different clades of AAA+ proteins and structural details and reclassification pertaining to proteins in each clade are described. Finally, two well-known AAA+ proteins, NSF and its close relative p97, are reviewed in detail.
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Affiliation(s)
- Yousuf A Khan
- Department of Molecular and Cellular Physiology, Stanford University, Stanford, CA, USA.,Department of Neurology and Neurological Sciences, Stanford University, Stanford, CA, USA.,Department of Structural Biology, Stanford University, Stanford, CA, USA.,Department of Photon Science, Stanford University, Stanford, CA, USA.,Center for Biomedical Informatics Research, Stanford University, Stanford, CA, USA
| | - K Ian White
- Department of Molecular and Cellular Physiology, Stanford University, Stanford, CA, USA.,Department of Neurology and Neurological Sciences, Stanford University, Stanford, CA, USA.,Department of Structural Biology, Stanford University, Stanford, CA, USA.,Department of Photon Science, Stanford University, Stanford, CA, USA.,Howard Hughes Medical Institute, Stanford University, Stanford, CA, USA
| | - Axel T Brunger
- Department of Molecular and Cellular Physiology, Stanford University, Stanford, CA, USA.,Department of Neurology and Neurological Sciences, Stanford University, Stanford, CA, USA.,Department of Structural Biology, Stanford University, Stanford, CA, USA.,Department of Photon Science, Stanford University, Stanford, CA, USA.,Howard Hughes Medical Institute, Stanford University, Stanford, CA, USA
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12
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Motone K, Cardozo N, Nivala J. Herding cats: Label-based approaches in protein translocation through nanopore sensors for single-molecule protein sequence analysis. iScience 2021; 24:103032. [PMID: 34527891 PMCID: PMC8433247 DOI: 10.1016/j.isci.2021.103032] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Abstract
Proteins carry out life's essential functions. Comprehensive proteome analysis technologies are thus required for a full understanding of the operating principles of biological systems. While current proteomics techniques suffer from limitations in sensitivity and/or throughput, nanopore technology has the potential to enable de novo protein identification through single-molecule sequencing. However, a significant barrier to achieving this goal is controlling protein/peptide translocation through the nanopore sensor for processive strand analysis. Here, we review recent approaches that use a range of techniques, from oligonucleotide conjugation to molecular motors, aimed at driving protein strands and peptides through protein nanopores. We further discuss site-specific protein conjugation chemistry that could be combined with these translocation approaches as future directions to achieve single-molecule protein detection and sequencing of native proteins.
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Affiliation(s)
- Keisuke Motone
- Paul G. Allen School of Computer Science and Engineering, University of Washington, Seattle, WA, USA
| | - Nicolas Cardozo
- Paul G. Allen School of Computer Science and Engineering, University of Washington, Seattle, WA, USA
| | - Jeff Nivala
- Paul G. Allen School of Computer Science and Engineering, University of Washington, Seattle, WA, USA
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13
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Damre M, Dayananda A, Varikoti RA, Stan G, Dima RI. Factors underlying asymmetric pore dynamics of disaggregase and microtubule-severing AAA+ machines. Biophys J 2021; 120:3437-3454. [PMID: 34181904 PMCID: PMC8391056 DOI: 10.1016/j.bpj.2021.05.027] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2020] [Revised: 04/11/2021] [Accepted: 05/19/2021] [Indexed: 11/26/2022] Open
Abstract
Disaggregation and microtubule-severing nanomachines from the AAA+ (ATPases associated with various cellular activities) superfamily assemble into ring-shaped hexamers that enable protein remodeling by coupling large-scale conformational changes with application of mechanical forces within a central pore by loops protruding within the pore. We probed the asymmetric pore motions and intraring interactions that support them by performing extensive molecular dynamics simulations of single-ring severing proteins and the double-ring disaggregase ClpB. Simulations reveal that dynamic stability of hexameric pores of severing proteins and of the nucleotide-binding domain 1 (NBD1) ring of ClpB, which belong to the same clade, involves a network of salt bridges that connect conserved motifs of central pore loops. Clustering analysis of ClpB highlights correlated motions of domains of neighboring protomers supporting strong interprotomer collaboration. Severing proteins have weaker interprotomer coupling and stronger intraprotomer stabilization through salt bridges involving pore loops. Distinct mechanisms are identified in the NBD2 ring of ClpB involving weaker interprotomer coupling through salt bridges formed by noncanonical loops and stronger intraprotomer coupling. Analysis of collective motions of PL1 loops indicates that the largest amplitude motions in the spiral complex of spastin and ClpB involve axial excursions of the loops, whereas for katanin they involve opening and closing of the central pore. All three motors execute primarily axial excursions in the ring complex. These results suggest distinct substrate processing mechanisms of remodeling and translocation by ClpB and spastin compared to katanin, thus providing dynamic support for the differential action of the two severing proteins. Relaxation dynamics of the distance between the PL1 loops and the center of mass of protomers reveals observation-time-dependent dynamics, leading to predicted relaxation times of tens to hundreds of microseconds on millisecond experimental timescales. For ClpB, the predicted relaxation time is in excellent agreement with the extracted time from smFRET experiments.
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Affiliation(s)
- Mangesh Damre
- Department of Chemistry, University of Cincinnati, Cincinnati, Ohio
| | - Ashan Dayananda
- Department of Chemistry, University of Cincinnati, Cincinnati, Ohio
| | | | - George Stan
- Department of Chemistry, University of Cincinnati, Cincinnati, Ohio.
| | - Ruxandra I Dima
- Department of Chemistry, University of Cincinnati, Cincinnati, Ohio.
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14
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Maksudov F, Jones LK, Barsegov V. Statistical Learning from Single-Molecule Experiments: Support Vector Machines and Expectation-Maximization Approaches to Understanding Protein Unfolding Data. J Phys Chem B 2021; 125:5794-5808. [PMID: 34075752 DOI: 10.1021/acs.jpcb.1c02334] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
Single-molecule force spectroscopy has become a powerful tool for the exploration of dynamic processes that involve proteins; yet, meaningful interpretation of the experimental data remains challenging. Owing to low signal-to-noise ratio, experimental force-extension spectra contain force signals due to nonspecific interactions, tip or substrate detachment, and protein desorption. Unravelling of complex protein structures results in the unfolding transitions of different types. Here, we test the performance of Support Vector Machines (SVM) and Expectation Maximization (EM) approaches in statistical learning from dynamic force experiments. When the output from molecular modeling in silico (or other studies) is used as a training set, SVM and EM can be applied to understand the unfolding force data. The maximal margin or maximum likelihood classifier can be used to separate experimental test observations into the unfolding transitions of different types, and EM optimization can then be utilized to resolve the statistics of unfolding forces: weights, average forces, and standard deviations. We designed an EM-based approach, which can be directly applied to the experimental data without data classification and division into training and test observations. This approach performs well even when the sample size is small and when the unfolding transitions are characterized by overlapping force ranges.
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15
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Mawla GD, Hall BM, Cárcamo-Oyarce G, Grant RA, Zhang JJ, Kardon JR, Ribbeck K, Sauer RT, Baker TA. ClpP1P2 peptidase activity promotes biofilm formation in Pseudomonas aeruginosa. Mol Microbiol 2021; 115:1094-1109. [PMID: 33231899 PMCID: PMC8141546 DOI: 10.1111/mmi.14649] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2020] [Revised: 11/15/2020] [Accepted: 11/16/2020] [Indexed: 01/07/2023]
Abstract
Caseinolytic proteases (Clp) are central to bacterial proteolysis and control cellular physiology and stress responses. They are composed of a double-ring compartmentalized peptidase (ClpP) and a AAA+ unfoldase (ClpX or ClpA/ClpC). Unlike many bacteria, the opportunistic pathogen Pseudomonas aeruginosa contains two ClpP homologs: ClpP1 and ClpP2. The specific functions of these homologs, however, are largely elusive. Here, we report that the active form of PaClpP2 is a part of a heteromeric PaClpP17 P27 tetradecamer that is required for proper biofilm development. PaClpP114 and PaClpP17 P27 complexes exhibit distinct peptide cleavage specificities and interact differentially with P. aeruginosa ClpX and ClpA. Crystal structures reveal that PaClpP2 has non-canonical features in its N- and C-terminal regions that explain its poor interaction with unfoldases. However, experiments in vivo indicate that the PaClpP2 peptidase active site uniquely contributes to biofilm development. These data strongly suggest that the specificity of different classes of ClpP peptidase subunits contributes to the biological outcome of proteolysis. This specialized role of PaClpP2 highlights it as an attractive target for developing antimicrobial agents that interfere specifically with late-stage P. aeruginosa development.
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Affiliation(s)
- Gina D. Mawla
- Department of Biology, Massachusetts Institute of Technology, Cambridge, MA 02139
| | - Branwen M. Hall
- Department of Biology, Massachusetts Institute of Technology, Cambridge, MA 02139
| | - Gerardo Cárcamo-Oyarce
- Department of Biological Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139
| | - Robert A. Grant
- Department of Biology, Massachusetts Institute of Technology, Cambridge, MA 02139
| | - Jia Jia Zhang
- Department of Biology, Massachusetts Institute of Technology, Cambridge, MA 02139
| | - Julia R. Kardon
- Department of Biology, Massachusetts Institute of Technology, Cambridge, MA 02139
| | - Katharina Ribbeck
- Department of Biological Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139
| | - Robert T. Sauer
- Department of Biology, Massachusetts Institute of Technology, Cambridge, MA 02139
| | - Tania A. Baker
- Department of Biology, Massachusetts Institute of Technology, Cambridge, MA 02139
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16
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Brötz-Oesterhelt H, Vorbach A. Reprogramming of the Caseinolytic Protease by ADEP Antibiotics: Molecular Mechanism, Cellular Consequences, Therapeutic Potential. Front Mol Biosci 2021; 8:690902. [PMID: 34109219 PMCID: PMC8182300 DOI: 10.3389/fmolb.2021.690902] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2021] [Accepted: 04/28/2021] [Indexed: 12/14/2022] Open
Abstract
Rising antibiotic resistance urgently calls for the discovery and evaluation of novel antibiotic classes and unique antibiotic targets. The caseinolytic protease Clp emerged as an unprecedented target for antibiotic therapy 15 years ago when it was observed that natural product-derived acyldepsipeptide antibiotics (ADEP) dysregulated its proteolytic core ClpP towards destructive proteolysis in bacterial cells. A substantial database has accumulated since on the interaction of ADEP with ClpP, which is comprehensively compiled in this review. On the molecular level, we describe the conformational control that ADEP exerts over ClpP, the nature of the protein substrates degraded, and the emerging structure-activity-relationship of the ADEP compound class. On the physiological level, we review the multi-faceted antibacterial mechanism, species-dependent killing modes, the activity against carcinogenic cells, and the therapeutic potential of the compound class.
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Affiliation(s)
- Heike Brötz-Oesterhelt
- Microbial Bioactive Compounds, Interfaculty Institute of Microbiology and Infection Medicine, University of Tuebingen, Tübingen, Germany.,Cluster of Excellence: Controlling Microbes to Fight Infection, Tübingen, Germany
| | - Andreas Vorbach
- Microbial Bioactive Compounds, Interfaculty Institute of Microbiology and Infection Medicine, University of Tuebingen, Tübingen, Germany
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17
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Kotamarthi HC, Sauer RT, Baker TA. The Non-dominant AAA+ Ring in the ClpAP Protease Functions as an Anti-stalling Motor to Accelerate Protein Unfolding and Translocation. Cell Rep 2021; 30:2644-2654.e3. [PMID: 32101742 DOI: 10.1016/j.celrep.2020.01.110] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2019] [Revised: 11/25/2019] [Accepted: 01/30/2020] [Indexed: 10/24/2022] Open
Abstract
ATP-powered unfoldases containing D1 and D2 AAA+ rings play important roles in protein homeostasis, but uncertainty about the function of each ring remains. Here we use single-molecule optical tweezers to assay mechanical unfolding and translocation by a variant of the ClpAP protease containing an ATPase-inactive D1 ring. This variant displays substantial mechanical defects in both unfolding and translocation of protein substrates. Notably, when D1 is hydrolytically inactive, ClpAP often stalls for times as long as minutes, and the substrate can back-slip through the enzyme when ATP concentrations are low. The inactive D1 variant also has more difficulty traveling in the N-to-C direction on a polypeptide track than it does moving in a C-to-N direction. These results indicate that D1 normally functions as an auxiliary/regulatory motor to promote uninterrupted enzyme advancement that is fueled largely by the D2 ring.
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Affiliation(s)
- Hema Chandra Kotamarthi
- Department of Biology, Massachusetts Institute of Technology, Cambridge, MA, USA; Howard Hughes Medical Institute, Massachusetts Institute of Technology, Cambridge, MA, USA
| | - Robert T Sauer
- Department of Biology, Massachusetts Institute of Technology, Cambridge, MA, USA.
| | - Tania A Baker
- Department of Biology, Massachusetts Institute of Technology, Cambridge, MA, USA; Howard Hughes Medical Institute, Massachusetts Institute of Technology, Cambridge, MA, USA.
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18
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Tremblay CY, Vass RH, Vachet RW, Chien P. The Cleavage Profile of Protein Substrates by ClpXP Reveals Deliberate Starts and Pauses. Biochemistry 2020; 59:4294-4301. [PMID: 33135889 DOI: 10.1021/acs.biochem.0c00553] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Cells rely on protein degradation by AAA+ proteases. A well-known example is the hexameric ClpX unfoldase, which captures ATP hydrolysis to feed substrates into the oligomeric ClpP peptidase. Recent studies show that an asymmetric ClpX spiral cycles protein translocation upon ATP hydrolysis. However, how this cycle affects peptide products is less explored in part because ClpP cleavage is thought to be solely defined by sequence constraints. Here, we comprehensively characterize peptides from Caulobacter crescentus ClpXP degradation of three different substrates using high-resolution mass spectrometry and find that cleavage of translocated substrates is driven by factors other than sequence. We report that defined locations in a translocated protein are especially sensitive to cleavage spaced on average every 10-13 residues. These sites are not exclusively controlled by sequence and are independent of bulk changes in catalytic peptidase sites, ATP hydrolysis, or the efficiency of initial recognition. These results fit a model in which processive translocation through ClpX starts at a specific location in a polypeptide and pauses during reset of the ClpX hexamer after a cycle of translocation. Our work suggests that defined peptides, which could be used as signaling molecules, can be generated from a given substrate by a nonspecific peptidase.
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Affiliation(s)
- Catherine Y Tremblay
- Department of Chemistry, University of Massachusetts, Amherst, Massachusetts 01003, United States
| | - Robert H Vass
- Department of Biochemistry and Molecular Biology, University of Massachusetts, Amherst, Massachusetts 01003, United States
| | - Richard W Vachet
- Department of Chemistry, University of Massachusetts, Amherst, Massachusetts 01003, United States
| | - Peter Chien
- Department of Biochemistry and Molecular Biology, University of Massachusetts, Amherst, Massachusetts 01003, United States
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19
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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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20
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Scull NW, Lucius AL. Kinetic Analysis of AAA+ Translocases by Combined Fluorescence and Anisotropy Methods. Biophys J 2020; 119:1335-1350. [PMID: 32997959 DOI: 10.1016/j.bpj.2020.08.018] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2020] [Revised: 08/03/2020] [Accepted: 08/17/2020] [Indexed: 11/30/2022] Open
Abstract
The multitude of varied, energy-dependent processes that exist in the cell necessitate a diverse array of macromolecular machines to maintain homeostasis, allow for growth, and facilitate reproduction. ATPases associated with various cellular activity are a set of protein assemblies that function as molecular motors to couple the energy of nucleoside triphosphate binding and hydrolysis to mechanical movement along a polymer lattice. A recent boom in structural insights into these motors has led to structural hypotheses on how these motors fulfill their function. However, in many cases, we lack direct kinetic measurements of the dynamic processes these motors undergo as they transition between observed structural states. Consequently, there is a need for improved techniques for testing the structural hypotheses in solution. Here, we apply transient-state fluorescence anisotropy and total fluorescence stopped-flow methods to the analysis of polypeptide translocation catalyzed by these ATPase motors. We specifically focus on the Hsp100-Clp protein system of ClpA, which is a well-studied, model ATPases associated with various cellular activity system that has both eukaryotic and archaea homologs. Using this system, we show that we can reproduce previously established kinetic parameters from the simultaneous analysis of fluorescence anisotropy and total fluorescence and overcome previous limitations of our previous approach. Specifically, for the first time, to our knowledge, we obtain quantitative interpretations of the translocation of polypeptide substrates longer than 100 aa.
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Affiliation(s)
- Nathaniel W Scull
- Department of Chemistry, University of Alabama at Birmingham, Birmingham, Alabama
| | - Aaron L Lucius
- Department of Chemistry, University of Alabama at Birmingham, Birmingham, Alabama.
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21
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The SecA motor generates mechanical force during protein translocation. Nat Commun 2020; 11:3802. [PMID: 32732903 PMCID: PMC7393111 DOI: 10.1038/s41467-020-17561-2] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2020] [Accepted: 07/07/2020] [Indexed: 12/31/2022] Open
Abstract
The Sec translocon moves proteins across lipid bilayers in all cells. The Sec channel enables passage of unfolded proteins through the bacterial plasma membrane, driven by the cytosolic ATPase SecA. Whether SecA generates mechanical force to overcome barriers to translocation posed by structured substrate proteins is unknown. Here, we kinetically dissect Sec-dependent translocation by monitoring translocation of a folded substrate protein with tunable stability at high time resolution. We find that substrate unfolding constitutes the rate-limiting step during translocation. Using single-molecule force spectroscopy, we also define the response of the protein to mechanical force. Relating the kinetic and force measurements reveals that SecA generates at least 10 piconewtons of mechanical force to actively unfold translocating proteins, comparable to cellular unfoldases. Combining biochemical and single-molecule measurements thus allows us to define how the SecA motor ensures efficient and robust export of proteins that contain stable structure. The ATPase SecA drives Sec-dependent protein translocation across the bacterial plasma membrane. Here, the authors combine kinetic translocation measurements with single-molecule force spectroscopy and demonstrate that the SecA motor generates mechanical force to unfold and translocate preproteins.
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22
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Torres-Delgado A, Kotamarthi HC, Sauer RT, Baker TA. The Intrinsically Disordered N-terminal Extension of the ClpS Adaptor Reprograms Its Partner AAA+ ClpAP Protease. J Mol Biol 2020; 432:4908-4921. [PMID: 32687854 DOI: 10.1016/j.jmb.2020.07.007] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2020] [Revised: 07/13/2020] [Accepted: 07/13/2020] [Indexed: 11/18/2022]
Abstract
Adaptor proteins modulate substrate selection by AAA+ proteases. The ClpS adaptor delivers N-degron substrates to ClpAP but inhibits degradation of substrates bearing ssrA tags or other related degrons. How ClpS inhibits degradation of such substrates is poorly understood. Here, we demonstrate that ClpS impedes recognition of ssrA-tagged substrates by a non-competitive mechanism and also slows subsequent unfolding/translocation of these substrates as well as of N-degron substrates. This suppression of mechanical activity is largely a consequence of the ability of ClpS to repress ATP hydrolysis by ClpA, but several lines of evidence show that ClpS's inhibition of substrate binding and its ATPase repression are separable activities. Using ClpS mutants and ClpS-ClpA chimeras, we establish that engagement of the intrinsically disordered N-terminal extension of ClpS by ClpA is both necessary and sufficient to inhibit multiple steps of ClpAP-catalyzed degradation. These observations reveal how an adaptor can simultaneously modulate the catalytic activity of a AAA+ enzyme, efficiently promote recognition of some substrates, suppress recognition of other substrates, and thereby affect degradation of its menu of substrates in a specific manner. We propose that similar mechanisms are likely to be used by other adaptors to regulate substrate choice and the catalytic activity of molecular machines.
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Affiliation(s)
- Amaris Torres-Delgado
- Department of Biology, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
| | | | - Robert T Sauer
- 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.
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23
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Lopez KE, Rizo AN, Tse E, Lin J, Scull NW, Thwin AC, Lucius AL, Shorter J, Southworth DR. Conformational plasticity of the ClpAP AAA+ protease couples protein unfolding and proteolysis. Nat Struct Mol Biol 2020; 27:406-416. [PMID: 32313240 PMCID: PMC7529148 DOI: 10.1038/s41594-020-0409-5] [Citation(s) in RCA: 41] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2019] [Accepted: 03/09/2020] [Indexed: 11/09/2022]
Abstract
The ClpAP complex is a conserved bacterial protease that unfolds and degrades proteins targeted for destruction. The ClpA double-ring hexamer powers substrate unfolding and translocation into the ClpP proteolytic chamber. Here, we determined high-resolution structures of wild-type Escherichia coli ClpAP undergoing active substrate unfolding and proteolysis. A spiral of pore loop-substrate contacts spans both ClpA AAA+ domains. Protomers at the spiral seam undergo nucleotide-specific rearrangements, supporting substrate translocation. IGL loops extend flexibly to bind the planar, heptameric ClpP surface with the empty, symmetry-mismatched IGL pocket maintained at the seam. Three different structures identify a binding-pocket switch by the IGL loop of the lowest positioned protomer, involving release and re-engagement with the clockwise pocket. This switch is coupled to a ClpA rotation and a network of conformational changes across the seam, suggesting that ClpA can rotate around the ClpP apical surface during processive steps of translocation and proteolysis.
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Affiliation(s)
- Kyle E Lopez
- Graduate Program in Biophysics, University of California, San Francisco, San Francisco, CA, USA
- Department of Biochemistry and Biophysics, Institute for Neurodegenerative Diseases, University of California, San Francisco, San Francisco, CA, USA
| | - Alexandrea N Rizo
- Department of Biochemistry and Biophysics, Institute for Neurodegenerative Diseases, University of California, San Francisco, San Francisco, CA, USA
- Graduate Program in Chemical Biology, University of Michigan, Ann Arbor, MI, USA
| | - Eric Tse
- Department of Biochemistry and Biophysics, Institute for Neurodegenerative Diseases, University of California, San Francisco, San Francisco, CA, USA
| | - JiaBei Lin
- Department of Biochemistry and Biophysics, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA, USA
| | - Nathaniel W Scull
- Department of Chemistry, The University of Alabama at Birmingham, Birmingham, AL, USA
| | - Aye C Thwin
- Department of Biochemistry and Biophysics, Institute for Neurodegenerative Diseases, University of California, San Francisco, San Francisco, CA, USA
| | - Aaron L Lucius
- Department of Chemistry, The University of Alabama at Birmingham, Birmingham, AL, USA
| | - James Shorter
- Department of Biochemistry and Biophysics, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA, USA
| | - Daniel R Southworth
- Department of Biochemistry and Biophysics, Institute for Neurodegenerative Diseases, University of California, San Francisco, San Francisco, CA, USA.
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24
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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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25
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Simultaneous sensing and imaging of individual biomolecular complexes enabled by modular DNA-protein coupling. Commun Chem 2020; 3:20. [PMID: 36703465 PMCID: PMC9814868 DOI: 10.1038/s42004-020-0267-4] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2019] [Accepted: 01/17/2020] [Indexed: 01/29/2023] Open
Abstract
Many proteins form dynamic complexes with DNA, RNA, and other proteins, which often involves protein conformational changes that are key to function. Yet, methods to probe these critical dynamics are scarce. Here we combine optical tweezers with fluorescence imaging to simultaneously monitor the conformation of individual proteins and their binding to partner proteins. Central is a protein-DNA coupling strategy, which uses exonuclease digestion and partial re-synthesis to generate DNA overhangs of different lengths, and ligation to oligo-labeled proteins. It provides up to 40 times higher coupling yields than existing protocols and enables new fluorescence-tweezers assays, which require particularly long and strong DNA handles. We demonstrate the approach by detecting the emission of a tethered fluorescent protein and of a molecular chaperone (trigger factor) complexed with its client. We conjecture that our strategy will be an important tool to study conformational dynamics within larger biomolecular complexes.
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26
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Avellaneda MJ, Franke KB, Sunderlikova V, Bukau B, Mogk A, Tans SJ. Processive extrusion of polypeptide loops by a Hsp100 disaggregase. Nature 2020; 578:317-320. [PMID: 31996849 DOI: 10.1038/s41586-020-1964-y] [Citation(s) in RCA: 66] [Impact Index Per Article: 16.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2019] [Accepted: 12/03/2019] [Indexed: 01/13/2023]
Abstract
The ability to reverse protein aggregation is vital to cells1,2. Hsp100 disaggregases such as ClpB and Hsp104 are proposed to catalyse this reaction by translocating polypeptide loops through their central pore3,4. This model of disaggregation is appealing, as it could explain how polypeptides entangled within aggregates can be extracted and subsequently refolded with the assistance of Hsp704,5. However, the model is also controversial, as the necessary motor activity has not been identified6-8 and recent findings indicate non-processive mechanisms such as entropic pulling or Brownian ratcheting9,10. How loop formation would be accomplished is also obscure. Indeed, cryo-electron microscopy studies consistently show single polypeptide strands in the Hsp100 pore11,12. Here, by following individual ClpB-substrate complexes in real time, we unambiguously demonstrate processive translocation of looped polypeptides. We integrate optical tweezers with fluorescent-particle tracking to show that ClpB translocates both arms of the loop simultaneously and switches to single-arm translocation when encountering obstacles. ClpB is notably powerful and rapid; it exerts forces of more than 50 pN at speeds of more than 500 residues per second in bursts of up to 28 residues. Remarkably, substrates refold while exiting the pore, analogous to co-translational folding. Our findings have implications for protein-processing phenomena including ubiquitin-mediated remodelling by Cdc48 (or its mammalian orthologue p97)13 and degradation by the 26S proteasome14.
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Affiliation(s)
| | - Kamila B Franke
- Center for Molecular Biology of Heidelberg University, German Cancer Research Center, Heidelberg, Germany
| | | | - Bernd Bukau
- Center for Molecular Biology of Heidelberg University, German Cancer Research Center, Heidelberg, Germany
| | - Axel Mogk
- Center for Molecular Biology of Heidelberg University, German Cancer Research Center, Heidelberg, Germany
| | - Sander J Tans
- AMOLF, Amsterdam, The Netherlands. .,Department of Bionanoscience, Kavli Institute of Nanoscience Delft, Delft University of Technology, Delft, The Netherlands.
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27
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Dima RI, Stan G. Computational Studies of Mechanical Remodeling of Substrate Proteins by AAA+ Biological Nanomachines. ACS SYMPOSIUM SERIES 2020. [DOI: 10.1021/bk-2020-1356.ch008] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Affiliation(s)
- Ruxandra I. Dima
- Department of Chemistry, University of Cincinnati, P. O. Box 210172, Cincinnati, Ohio 45221, United States
| | - George Stan
- Department of Chemistry, University of Cincinnati, P. O. Box 210172, Cincinnati, Ohio 45221, United States
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28
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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: 126] [Impact Index Per Article: 25.2] [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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29
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A Mechanistic Perspective on PEX1 and PEX6, Two AAA+ Proteins of the Peroxisomal Protein Import Machinery. Int J Mol Sci 2019; 20:ijms20215246. [PMID: 31652724 PMCID: PMC6862443 DOI: 10.3390/ijms20215246] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2019] [Revised: 10/18/2019] [Accepted: 10/21/2019] [Indexed: 12/11/2022] Open
Abstract
In contrast to many protein translocases that use ATP or GTP hydrolysis as the driving force to transport proteins across biological membranes, the peroxisomal matrix protein import machinery relies on a regulated self-assembly mechanism for this purpose and uses ATP hydrolysis only to reset its components. The ATP-dependent protein complex in charge of resetting this machinery—the Receptor Export Module (REM)—comprises two members of the “ATPases Associated with diverse cellular Activities” (AAA+) family, PEX1 and PEX6, and a membrane protein that anchors the ATPases to the organelle membrane. In recent years, a large amount of data on the structure/function of the REM complex has become available. Here, we discuss the main findings and their mechanistic implications.
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30
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Pill MF, East ALL, Marx D, Beyer MK, Clausen‐Schaumann H. Mechanical Activation Drastically Accelerates Amide Bond Hydrolysis, Matching Enzyme Activity. Angew Chem Int Ed Engl 2019; 58:9787-9790. [DOI: 10.1002/anie.201902752] [Citation(s) in RCA: 30] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2019] [Revised: 05/10/2019] [Indexed: 01/21/2023]
Affiliation(s)
- Michael F. Pill
- Department of Applied Sciences and MechatronicsMunich University of Applied Sciences Lothstrasse 34 80334 Munich Germany
- Center for Nanoscience (CeNS) Schellingstrasse 4 80799 Munich Germany
| | - Allan L. L. East
- Department of Chemistry and BiochemistryUniversity of Regina Regina SK S4S0A2 Canada
| | - Dominik Marx
- Lehrstuhl für Theoretische ChemieRuhr-Universität Bochum 44780 Bochum Germany
| | - Martin K. Beyer
- Institut für Ionenphysik und Angewandte PhysikUniversität Innsbruck Technikerstrasse 25 6020 Innsbruck Austria
| | - Hauke Clausen‐Schaumann
- Department of Applied Sciences and MechatronicsMunich University of Applied Sciences Lothstrasse 34 80334 Munich Germany
- Center for Nanoscience (CeNS) Schellingstrasse 4 80799 Munich Germany
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31
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Abstract
AAA+ proteolytic machines use energy from ATP hydrolysis to degrade damaged, misfolded, or unneeded proteins. Protein degradation occurs within a barrel-shaped self-compartmentalized peptidase. Before protein substrates can enter this peptidase, they must be unfolded and then translocated through the axial pore of an AAA+ ring hexamer. An unstructured region of the protein substrate is initially engaged in the axial pore, and conformational changes in the ring, powered by ATP hydrolysis, generate a mechanical force that pulls on and denatures the substrate. The same conformational changes in the hexameric ring then mediate mechanical translocation of the unfolded polypeptide into the peptidase chamber. For the bacterial ClpXP and ClpAP AAA+ proteases, the mechanical activities of protein unfolding and translocation have been directly visualized by single-molecule optical trapping. These studies in combination with structural and biochemical experiments illuminate many principles that underlie this universal mechanism of ATP-fueled protein unfolding and subsequent destruction.
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Affiliation(s)
- Adrian O Olivares
- Department of Biochemistry, Vanderbilt University School of Medicine, Nashville, Tennessee 37232, USA
| | - Tania A Baker
- Howard Hughes Medical Institute and 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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32
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Pill MF, East ALL, Marx D, Beyer MK, Clausen‐Schaumann H. Mechanische Aktivierung beschleunigt die Hydrolyse der Amidbindung drastisch, vergleichbar der Aktivität von Enzymen. Angew Chem Int Ed Engl 2019. [DOI: 10.1002/ange.201902752] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Affiliation(s)
- Michael F. Pill
- Fakultät für angewandte Naturwissenschaften und MechatronikHochschule für angewandte Wissenschaften München Lothstraße 34 80334 München Deutschland
- Center for Nanoscience (CeNS) Schellingstraße 4 80799 München Deutschland
| | - Allan L. L. East
- Department of Chemistry and BiochemistryUniversity of Regina Regina SK S4S0A2 Kanada
| | - Dominik Marx
- Lehrstuhl für Theoretische ChemieRuhr-Universität Bochum 44780 Bochum Deutschland
| | - Martin K. Beyer
- Institut für Ionenphysik und Angewandte PhysikUniversität Innsbruck Technikerstraße 25 6020 Innsbruck Österreich
| | - Hauke Clausen‐Schaumann
- Fakultät für angewandte Naturwissenschaften und MechatronikHochschule für angewandte Wissenschaften München Lothstraße 34 80334 München Deutschland
- Center for Nanoscience (CeNS) Schellingstraße 4 80799 München Deutschland
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33
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Duran EC, Lucius AL. Examination of the nucleotide-linked assembly mechanism of E. coli ClpA. Protein Sci 2019; 28:1312-1323. [PMID: 31054177 DOI: 10.1002/pro.3638] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2019] [Revised: 04/23/2019] [Accepted: 04/24/2019] [Indexed: 11/08/2022]
Abstract
Escherichia coli ClpA is a AAA+ (ATPase Associated with diverse cellular Activities) chaperone that catalyzes the ATP-dependent unfolding and translocation of substrate proteins targeted for degradation by a protease, ClpP. ClpA hexamers associate with one or both ends of ClpP tetradecamers to form ClpAP complexes. Each ClpA protomer contains two nucleotide-binding sites, NBD1 and NBD2, and self-assembly into hexamers is thermodynamically linked to nucleotide binding. Despite a number of studies aimed at characterizing ClpA and ClpAP-catalyzed substrate unfolding and degradation, respectively, to date the field is unable to quantify the concentration of ClpA hexamers available to interact with ClpP for any given nucleotide and total ClpA concentration. In this work, sedimentation velocity studies are used to quantitatively examine the self-assembly of a ClpA Walker B variant in the presence of ATP. In addition to the hexamerization, we observe the formation of a previously unreported ClpA dodecamer in the presence of ATP. Further, we report apparent equilibrium constants for the formation of each ClpA oligomer obtained from direct boundary modeling of the sedimentation velocity data. The energetics of nucleotide binding to NBD1 and NBD2 are revealed by examining the dependence of the apparent association equilibrium constants on free nucleotide concentration.
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Affiliation(s)
- Elizabeth C Duran
- Chemistry Department, University of Alabama at Birmingham, Birmingham, Alabama, 35205
| | - Aaron L Lucius
- Chemistry Department, University of Alabama at Birmingham, Birmingham, Alabama, 35205
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Catipovic MA, Bauer BW, Loparo JJ, Rapoport TA. Protein translocation by the SecA ATPase occurs by a power-stroke mechanism. EMBO J 2019; 38:embj.2018101140. [PMID: 30877095 DOI: 10.15252/embj.2018101140] [Citation(s) in RCA: 37] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2018] [Revised: 01/25/2019] [Accepted: 01/31/2019] [Indexed: 11/09/2022] Open
Abstract
SecA belongs to the large class of ATPases that use the energy of ATP hydrolysis to perform mechanical work resulting in protein translocation across membranes, protein degradation, and unfolding. SecA translocates polypeptides through the SecY membrane channel during protein secretion in bacteria, but how it achieves directed peptide movement is unclear. Here, we use single-molecule FRET to derive a model that couples ATP hydrolysis-dependent conformational changes of SecA with protein translocation. Upon ATP binding, the two-helix finger of SecA moves toward the SecY channel, pushing a segment of the polypeptide into the channel. The finger retracts during ATP hydrolysis, while the clamp domain of SecA tightens around the polypeptide, preserving progress of translocation. The clamp opens after phosphate release and allows passive sliding of the polypeptide chain through the SecA-SecY complex until the next ATP binding event. This power-stroke mechanism may be used by other ATPases that move polypeptides.
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Affiliation(s)
- Marco A Catipovic
- Department of Cell Biology, Harvard Medical School, Boston, MA, USA.,Howard Hughes Medical Institute, Harvard Medical School, Boston, MA, USA
| | - Benedikt W Bauer
- Department of Cell Biology, Harvard Medical School, Boston, MA, USA.,Howard Hughes Medical Institute, Harvard Medical School, Boston, MA, USA
| | - Joseph J Loparo
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA, USA
| | - Tom A Rapoport
- Department of Cell Biology, Harvard Medical School, Boston, MA, USA .,Howard Hughes Medical Institute, Harvard Medical School, Boston, MA, USA
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Javidialesaadi A, Flournoy SM, Stan G. Role of Diffusion in Unfolding and Translocation of Multidomain Titin I27 Substrates by a Clp ATPase Nanomachine. J Phys Chem B 2019; 123:2623-2635. [DOI: 10.1021/acs.jpcb.8b10282] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Affiliation(s)
| | - Shanice M. Flournoy
- Department of Chemistry, Virginia State University, Petersburg, Virginia 23806, United States
| | - George Stan
- Department of Chemistry, University of Cincinnati, Cincinnati, Ohio 45221, United States
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36
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Duran EC, Lucius AL. ATP hydrolysis inactivating Walker B mutation perturbs E. coli ClpA self-assembly energetics in the absence of nucleotide. Biophys Chem 2018; 242:6-14. [PMID: 30173103 DOI: 10.1016/j.bpc.2018.08.005] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2018] [Revised: 08/22/2018] [Accepted: 08/23/2018] [Indexed: 02/03/2023]
Abstract
E. coli ClpA is an AAA+ (ATPase Associated with diverse cellular Activities) chaperone that catalyzes the ATP-dependent unfolding and translocation of substrate proteins for the purposes of proper proteome maintenance. Biologically active ClpA hexamers contain two nucleotide binding domains (NBD) per protomer, D1 and D2. Despite extensive study, complete understanding of how the twelve NBDs within a ClpA hexamer coordinate ATP binding and hydrolysis to polypeptide translocation is currently lacking. To examine nucleotide binding and coordination at D1 and D2, ClpA Walker B variants deficient in ATP hydrolysis at one or both NBDs have been employed in various studies. In the presence of ATP, it is widely assumed that ClpA Walker B variants are entirely hexameric. However, a thermodynamically rigorous examination of the self-assembly mechanism has not been obtained. Differences in the assembly due to the mutation can be misattributed to the active NBD, leading to potential misinterpretations of kinetic studies. Here we use sedimentation velocity studies to quantitatively examine the self-assembly mechanism of ClpA Walker B variants deficient in ATP hydrolysis at D1, D2, and both NBDs. We found that the Walker B mutations had clear, if modest, effects on the assembly. Most notably, the Walker B mutation stabilizes the population of a larger oligomer in the absence of nucleotide, that is not present for analogous concentrations of wild type ClpA. Our results indicate that Walker B mutants, widely used in studies of AAA+ family proteins, require additional characterization as the mutation affects not only ATP hydrolysis, but also the ligand linked assembly of these complexes. This linkage must be considered in investigations of unfolding or other ATP dependent functions.
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Affiliation(s)
- Elizabeth C Duran
- University of Alabama at Birmingham, Chemistry Department, Birmingham, AL, United States
| | - Aaron L Lucius
- University of Alabama at Birmingham, Chemistry Department, Birmingham, AL, United States.
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37
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Abstract
Regulated proteolysis is a vital process that affects all living things. Bacteria use energy-dependent AAA+ proteases to power degradation of misfolded and native regulatory proteins. Given that proteolysis is an irreversible event, specificity and selectivity in degrading substrates are key. Specificity is often augmented through the use of adaptors that modify the inherent specificity of the proteolytic machinery. Regulated protein degradation is intricately linked to quality control, cell-cycle progression, and physiological transitions. In this review, we highlight recent work that has shed light on our understanding of regulated proteolysis in bacteria. We discuss the role AAA+ proteases play during balanced growth as well as how these proteases are deployed during changes in growth. We present examples of how protease selectivity can be controlled in increasingly complex ways. Finally, we describe how coupling a core recognition determinant to one or more modifying agents is a general theme for regulated protein degradation.
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Affiliation(s)
- Samar A Mahmoud
- Department of Biochemistry and Molecular Biology, University of Massachusetts Amherst, Amherst, Massachusetts 01003, USA; ,
| | - Peter Chien
- Department of Biochemistry and Molecular Biology, University of Massachusetts Amherst, Amherst, Massachusetts 01003, USA; ,
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38
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Cotranslocational processing of the protein substrate calmodulin by an AAA+ unfoldase occurs via unfolding and refolding intermediates. Proc Natl Acad Sci U S A 2018; 115:E4786-E4795. [PMID: 29735657 DOI: 10.1073/pnas.1721811115] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Protein remodeling by AAA+ enzymes is central for maintaining proteostasis in a living cell. However, a detailed structural description of how this is accomplished at the level of the substrate molecules that are acted upon is lacking. Here, we combine chemical cross-linking and methyl transverse relaxation-optimized NMR spectroscopy to study, at atomic resolution, the stepwise unfolding and subsequent refolding of the two-domain substrate calmodulin by the VAT AAA+ unfoldase from Thermoplasma acidophilum By engineering intermolecular disulphide bridges between the substrate and VAT we trap the substrate at different stages of translocation, allowing structural studies throughout the translocation process. Our results show that VAT initiates substrate translocation by pulling on intrinsically unstructured N or C termini of substrate molecules without showing specificity for a particular amino acid sequence. Although the B1 domain of protein G is shown to unfold cooperatively, translocation of calmodulin leads to the formation of intermediates, and these differ on an individual domain level in a manner that depends on whether pulling is from the N or C terminus. The approach presented generates an atomic resolution picture of substrate unfolding and subsequent refolding by unfoldases that can be quite different from results obtained via in vitro denaturation experiments.
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Cordova JC, Olivares AO, Lang MJ. Mechanically Watching the ClpXP Proteolytic Machinery. Methods Mol Biol 2018; 1486:317-341. [PMID: 27844434 DOI: 10.1007/978-1-4939-6421-5_12] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Energy-dependent protein degradation is studied through the dual bead ClpXP motility assay. Processing of folded proteins involves recognition, unfolding, translocation, and degradation stages. A dual optical trap, in a passive force-clamp geometry, exhibits bead-to-bead displacements that directly follow subprocesses underlying protein degradation. Discrete nanometer-scale displacements of the bead position reveal steps, dwells and pauses during the unfolding and translocation substeps. With a few structural modifications to the protease machinery and an engineered substrate, the assay represents a "chassis" for the measurement of a wide range of substrates and related machinery. The methods described faithfully record our assay as implemented, including substrate design, wet assay preparation, and the motility assay experiment protocol. The strategies herein permit adaptation of the ClpXP mechanical assay to a wide range of protein degradation systems.
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Affiliation(s)
- Juan Carlos Cordova
- Department of Chemical and Biomolecular Engineering, Vanderbilt University, 308-A Olin Hall, VU Mailbox: PMB 351604, Nashville, TN, 37235, USA
| | - Adrian O Olivares
- Department of Biology, Massachusetts Institute of Technology, Cambridge, MA, 02139, USA
| | - Matthew J Lang
- Department of Chemical and Biomolecular Engineering and Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, 308-A Olin Hall, VU Mailbox: PMB 351604, Nashville, TN, 37235, USA.
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The peroxisomal AAA-ATPase Pex1/Pex6 unfolds substrates by processive threading. Nat Commun 2018; 9:135. [PMID: 29321502 PMCID: PMC5762779 DOI: 10.1038/s41467-017-02474-4] [Citation(s) in RCA: 41] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2017] [Accepted: 12/04/2017] [Indexed: 12/15/2022] Open
Abstract
Pex1 and Pex6 form a heterohexameric motor essential for peroxisome biogenesis and function, and mutations in these AAA-ATPases cause most peroxisome-biogenesis disorders in humans. The tail-anchored protein Pex15 recruits Pex1/Pex6 to the peroxisomal membrane, where it performs an unknown function required for matrix-protein import. Here we determine that Pex1/Pex6 from S. cerevisiae is a protein translocase that unfolds Pex15 in a pore-loop-dependent and ATP-hydrolysis-dependent manner. Our structural studies of Pex15 in isolation and in complex with Pex1/Pex6 illustrate that Pex15 binds the N-terminal domains of Pex6, before its C-terminal disordered region engages with the pore loops of the motor, which then processively threads Pex15 through the central pore. Furthermore, Pex15 directly binds the cargo receptor Pex5, linking Pex1/Pex6 to other components of the peroxisomal import machinery. Our results thus support a role of Pex1/Pex6 in mechanical unfolding of peroxins or their extraction from the peroxisomal membrane during matrix-protein import. Pex1 and Pex6 form a heterohexameric Type-2 AAA-ATPase motor whose function in peroxisomal matrix-protein import is still debated. Here, the authors combine structural, biochemical, and cell-biological approaches to show that Pex1/Pex6 is a protein unfoldase, which supports a role in mechanical unfolding of peroxin proteins.
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41
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Gur E, Korman M, Hecht N, Regev O, Schlussel S, Silberberg N, Elharar Y. How to control an intracellular proteolytic system: Coordinated regulatory switches in the mycobacterial Pup-proteasome system. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2017; 1864:2253-2260. [PMID: 28887055 DOI: 10.1016/j.bbamcr.2017.08.012] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/19/2017] [Revised: 08/26/2017] [Accepted: 08/31/2017] [Indexed: 10/18/2022]
Abstract
Intracellular proteolysis is critical for the proper functioning of all cells, owing to its involvement in a wide range of processes. Because of the destructive nature of protein degradation, intracellular proteolysis is restricted by control mechanisms at almost every step of the proteolytic process. Understanding the coordination of such mechanisms is a challenging task, especially in systems as complex as the eukaryotic ubiquitin-proteasome system (UPS). In comparison, the bacterial analog of the UPS, the Pup-proteasome system (PPS) is much simpler and, therefore, allows for insight into the control of a proteolytic system. This review integrates available information to present a coherent picture of what is known of PPS regulatory switches and describes how these switches act in concert to enforce regulation at the system level. Finally, open questions regarding PPS regulation are discussed, providing readers with a sense of what lies ahead in the field.
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Affiliation(s)
- Eyal Gur
- Department of Life Sciences, Ben-Gurion University of the Negev, Beer-Sheva 84105, Israel; The National Institute for Biotechnology in the Negev, Ben-Gurion University of the Negev, Beer-Sheva 84105, Israel.
| | - Maayan Korman
- Department of Life Sciences, Ben-Gurion University of the Negev, Beer-Sheva 84105, Israel
| | - Nir Hecht
- Department of Life Sciences, Ben-Gurion University of the Negev, Beer-Sheva 84105, Israel
| | - Ofir Regev
- Department of Life Sciences, Ben-Gurion University of the Negev, Beer-Sheva 84105, Israel
| | - Shai Schlussel
- Department of Life Sciences, Ben-Gurion University of the Negev, Beer-Sheva 84105, Israel
| | - Nimrod Silberberg
- Department of Life Sciences, Ben-Gurion University of the Negev, Beer-Sheva 84105, Israel; The National Institute for Biotechnology in the Negev, Ben-Gurion University of the Negev, Beer-Sheva 84105, Israel
| | - Yifat Elharar
- Department of Life Sciences, Ben-Gurion University of the Negev, Beer-Sheva 84105, Israel
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42
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Katanin spiral and ring structures shed light on power stroke for microtubule severing. Nat Struct Mol Biol 2017; 24:717-725. [PMID: 28783150 PMCID: PMC7152510 DOI: 10.1038/nsmb.3448] [Citation(s) in RCA: 69] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2017] [Accepted: 07/07/2017] [Indexed: 01/07/2023]
Abstract
Microtubule-severing enzymes katanin, spastin and fidgetin are AAA ATPases important for the biogenesis and maintenance of complex microtubule arrays in axons, spindles and cilia. Because of a lack of known 3D structures for these enzymes, their mechanism of action has remained poorly understood. Here we report the X-ray crystal structure of the monomeric AAA katanin module from Caenorhabditis elegans and cryo-EM reconstructions of the hexamer in two conformations. The structures reveal an unexpected asymmetric arrangement of the AAA domains mediated by structural elements unique to microtubule-severing enzymes and critical for their function. The reconstructions show that katanin cycles between open spiral and closed ring conformations, depending on the ATP occupancy of a gating protomer that tenses or relaxes interprotomer interfaces. Cycling of the hexamer between these conformations would provide the power stroke for microtubule severing.
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43
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Duran EC, Weaver CL, Lucius AL. Comparative Analysis of the Structure and Function of AAA+ Motors ClpA, ClpB, and Hsp104: Common Threads and Disparate Functions. Front Mol Biosci 2017; 4:54. [PMID: 28824920 PMCID: PMC5540906 DOI: 10.3389/fmolb.2017.00054] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2017] [Accepted: 07/13/2017] [Indexed: 11/25/2022] Open
Abstract
Cellular proteostasis involves not only the expression of proteins in response to environmental needs, but also the timely repair or removal of damaged or unneeded proteins. AAA+ motor proteins are critically involved in these pathways. Here, we review the structure and function of AAA+ proteins ClpA, ClpB, and Hsp104. ClpB and Hsp104 rescue damaged proteins from toxic aggregates and do not partner with any protease. ClpA functions as the regulatory component of the ATP dependent protease complex ClpAP, and also remodels inactive RepA dimers into active monomers in the absence of the protease. Because ClpA functions both with and without a proteolytic component, it is an ideal system for developing strategies that address one of the major challenges in the study of protein remodeling machines: how do we observe a reaction in which the substrate protein does not undergo covalent modification? Here, we review experimental designs developed for the examination of polypeptide translocation catalyzed by the AAA+ motors in the absence of proteolytic degradation. We propose that transient state kinetic methods are essential for the examination of elementary kinetic mechanisms of these motor proteins. Furthermore, rigorous kinetic analysis must also account for the thermodynamic properties of these complicated systems that reside in a dynamic equilibrium of oligomeric states, including the biologically active hexamer.
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Affiliation(s)
- Elizabeth C Duran
- Department of Chemistry, University of Alabama at BirminghamBirmingham, AL, United States
| | - Clarissa L Weaver
- Department of Chemistry, University of Alabama at BirminghamBirmingham, AL, United States
| | - Aaron L Lucius
- Department of Chemistry, University of Alabama at BirminghamBirmingham, AL, United States
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44
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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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45
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Javidialesaadi A, Stan G. Asymmetric Conformational Transitions in AAA+ Biological Nanomachines Modulate Direction-Dependent Substrate Protein Unfolding Mechanisms. J Phys Chem B 2017; 121:7108-7121. [DOI: 10.1021/acs.jpcb.7b05963] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Affiliation(s)
| | - George Stan
- Department of Chemistry, University of Cincinnati, Cincinnati, Ohio 45221, United States
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46
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Kim Y, Li H, He Y, Chen X, Ma X, Lee M. Collective helicity switching of a DNA-coat assembly. NATURE NANOTECHNOLOGY 2017; 12:551-556. [PMID: 28346455 DOI: 10.1038/nnano.2017.42] [Citation(s) in RCA: 49] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/22/2016] [Accepted: 02/17/2017] [Indexed: 06/06/2023]
Abstract
Hierarchical assemblies of biomolecular subunits can carry out versatile tasks at the cellular level with remarkable spatial and temporal precision. As an example, the collective motion and mutual cooperation between complex protein machines mediate essential functions for life, such as replication, synthesis, degradation, repair and transport. Nucleic acid molecules are far less dynamic than proteins and need to bind to specific proteins to form hierarchical structures. The simplest example of these nucleic acid-based structures is provided by a rod-shaped tobacco mosaic virus, which consists of genetic material surrounded by coat proteins. Inspired by the complexity and hierarchical assembly of viruses, a great deal of effort has been devoted to design similarly constructed artificial viruses. However, such a wrapping approach makes nucleic acid dynamics insensitive to environmental changes. This limitation generally restricts, for example, the amplification of the conformational dynamics between the right-handed B form to the left-handed Z form of double-stranded deoxyribonucleic acid (DNA). Here we report a virus-like hierarchical assembly in which the native DNA and a synthetic coat undergo repeated collective helicity switching triggered by pH change under physiological conditions. We also show that this collective helicity inversion occurs during translocation of the DNA-coat assembly into intracellular compartments. Translating DNA conformational dynamics into a higher level of hierarchical dynamics may provide an approach to create DNA-based nanomachines.
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Affiliation(s)
- Yongju Kim
- State Key Laboratory of Supramolecular Structure and Materials, College of Chemistry, Jilin University, Changchun 130012, China
| | - Huichang Li
- State Key Laboratory of Supramolecular Structure and Materials, College of Chemistry, Jilin University, Changchun 130012, China
| | - Ying He
- State Key Laboratory of Supramolecular Structure and Materials, College of Chemistry, Jilin University, Changchun 130012, China
| | - Xi Chen
- State Key Laboratory of Supramolecular Structure and Materials, College of Chemistry, Jilin University, Changchun 130012, China
| | - Xiaoteng Ma
- State Key Laboratory of Supramolecular Structure and Materials, College of Chemistry, Jilin University, Changchun 130012, China
| | - Myongsoo Lee
- State Key Laboratory of Supramolecular Structure and Materials, College of Chemistry, Jilin University, Changchun 130012, China
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47
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Ryu JK, Jahn R, Yoon TY. Review: Progresses in understanding N-ethylmaleimide sensitive factor (NSF) mediated disassembly of SNARE complexes. Biopolymers 2017; 105:518-31. [PMID: 27062050 DOI: 10.1002/bip.22854] [Citation(s) in RCA: 46] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2016] [Revised: 03/19/2016] [Accepted: 04/06/2016] [Indexed: 11/09/2022]
Abstract
N-ethylmaleimide sensitive factor (NSF) is a key protein of intracellular membrane traffic. NSF is a highly conserved protein belonging to the ATPases associated with other activities (AAA+ proteins). AAA+ share common domains and all transduce ATP hydrolysis into major conformational movements that are used to carry out conformational work on client proteins. Together with its cofactor SNAP, NSF is specialized on disassembling highly stable SNARE complexes that form after each membrane fusion event. Although essential for all eukaryotic cells, however, the details of this reaction have long been enigmatic. Recently, major progress has been made in both elucidating the structure of NSF/SNARE complexes and in understanding the reaction mechanism. Advances in both cryo EM and single molecule measurements suggest that NSF, together with its cofactor SNAP, imposes a tight grip on the SNARE complex. After ATP hydrolysis and phosphate release, it then builds up mechanical tension that is ultimately used to rip apart the SNAREs in a single burst. Because the AAA domains are extremely well-conserved, the molecular mechanism elucidated for NSF is presumably shared by many other AAA+ ATPases. © 2016 Wiley Periodicals, Inc. Biopolymers 105: 518-531, 2016.
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Affiliation(s)
- Je-Kyung Ryu
- Department of Bionanoscience, Kavli Institute of Nanoscience, Delft University of Technology, Delft, CJ, 2628, the Netherlands
| | - Reinhard Jahn
- Department of Neurobiology, Max-Planck-Institute for Biophysical Chemistry, Göttingen, 37077, Germany
| | - Tae-Young Yoon
- Center for Nanomedicine, Institute for Basic Science (IBS) and Y-IBS Institute, Yonsei University, Seoul, 03722, South Korea
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48
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Two Isoforms of Clp Peptidase in Pseudomonas aeruginosa Control Distinct Aspects of Cellular Physiology. J Bacteriol 2017; 199:JB.00568-16. [PMID: 27849175 DOI: 10.1128/jb.00568-16] [Citation(s) in RCA: 30] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2016] [Accepted: 10/20/2016] [Indexed: 02/07/2023] Open
Abstract
Caseinolytic peptidases (ClpPs) regulate diverse aspects of cellular physiology in bacteria. Some species have multiple ClpPs, including the opportunistic pathogen Pseudomonas aeruginosa, in which there is an archetypical isoform, ClpP1, and a second isoform, ClpP2, about which little is known. Here, we use phenotypic assays to investigate the biological roles of ClpP1 and ClpP2 and biochemical assays to characterize purified ClpP1, ClpP2, ClpX, and ClpA. Interestingly, ClpP1 and ClpP2 have distinct intracellular roles for motility, pigment production, iron scavenging, and biofilm formation. Of particular interest, ClpP2, but not ClpP1, is required for microcolony organization, where multicellular organized structures first form on the pathway to biofilm production. We found that purified ClpP1 with ClpX or ClpA was enzymatically active, yet to our surprise, ClpP2 was inactive and not fully assembled in vitro; attempts to assist ClpP2 assembly and activation by mixing with the other Clp components failed to turn on ClpP2, as did solution conditions that have helped activate other ClpPs in vitro We postulate that the active form of ClpP2 has yet to be discovered, and we present several potential models to explain its activation as well as the unique role ClpP2 plays in the development of the clinically important biofilms in P. aeruginosaIMPORTANCEPseudomonas aeruginosa is responsible for severe infections of immunocompromised patients. Our work demonstrates that two different isoforms of the Clp peptidase, ClpP1 and ClpP2, control distinct aspects of cellular physiology for this organism. In particular, we identify ClpP2 as being necessary for microcolony organization. Pure active forms of ClpP1 and either ClpX or ClpA were characterized as assembled and active, and ClpP2 was incompletely assembled and inactive. By establishing both the unique biological roles of ClpP1 and ClpP2 and their initial biochemical assemblies, we have set the stage for important future work on the structure, function, and biological targets of Clp proteolytic enzymes in this important opportunistic pathogen.
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49
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Heuck A, Schitter-Sollner S, Suskiewicz MJ, Kurzbauer R, Kley J, Schleiffer A, Rombaut P, Herzog F, Clausen T. Structural basis for the disaggregase activity and regulation of Hsp104. eLife 2016; 5. [PMID: 27901467 PMCID: PMC5130295 DOI: 10.7554/elife.21516] [Citation(s) in RCA: 45] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2016] [Accepted: 11/22/2016] [Indexed: 11/13/2022] Open
Abstract
The Hsp104 disaggregase is a two-ring ATPase machine that rescues various forms of non-native proteins including the highly resistant amyloid fibers. The structural-mechanistic underpinnings of how the recovery of toxic protein aggregates is promoted and how this potent unfolding activity is prevented from doing collateral damage to cellular proteins are not well understood. Here, we present structural and biochemical data revealing the organization of Hsp104 from Chaetomium thermophilum at 3.7 Å resolution. We show that the coiled-coil domains encircling the disaggregase constitute a ‘restraint mask’ that sterically controls the mobility and thus the unfolding activity of the ATPase modules. In addition, we identify a mechanical linkage that coordinates the activity of the two ATPase rings and accounts for the high unfolding potential of Hsp104. Based on these findings, we propose a general model for how Hsp104 and related chaperones operate and are kept under control until recruited to appropriate substrates. DOI:http://dx.doi.org/10.7554/eLife.21516.001
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Affiliation(s)
- Alexander Heuck
- Research Institute of Molecular Pathology, Vienna Biocenter, Vienna, Austria
| | | | | | - Robert Kurzbauer
- Research Institute of Molecular Pathology, Vienna Biocenter, Vienna, Austria
| | - Juliane Kley
- Research Institute of Molecular Pathology, Vienna Biocenter, Vienna, Austria
| | | | - Pascaline Rombaut
- Gene Center and Department of Biochemistry, Ludwig-Maximilians University, Munich, Germany
| | - Franz Herzog
- Gene Center and Department of Biochemistry, Ludwig-Maximilians University, Munich, Germany
| | - Tim Clausen
- Research Institute of Molecular Pathology, Vienna Biocenter, Vienna, Austria
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50
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Abstract
Protein degradation is essential for all living things. Bacteria use energy-dependent proteases to control protein destruction in a highly specific manner. Recognition of substrates is determined by the inherent specificity of the proteases and through adaptor proteins that alter the spectrum of substrates. In the α-proteobacterium Caulobacter crescentus, regulated protein degradation is required for stress responses, developmental transitions, and cell cycle progression. In this review, we describe recent progress in our understanding of the regulated and stress-responsive protein degradation pathways in Caulobacter. We discuss how organization of highly specific adaptors into functional hierarchies drives destruction of proteins during the bacterial cell cycle. Because all cells must balance the need for degradation of many true substrates with the toxic consequences of nonspecific protein destruction, principles found in one system likely generalize to others.
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Affiliation(s)
| | - Peter Chien
- Department of Biochemistry and Molecular Biology, University of Massachusetts, Amherst, Massachusetts 01003;
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