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Abstract
Interest in bacterial proteasomes was sparked by the discovery that proteasomal degradation is required for the pathogenesis of Mycobacterium tuberculosis, one of the world's deadliest pathogens. Although bacterial proteasomes are structurally similar to their eukaryotic and archaeal homologs, there are key differences in their mechanisms of assembly, activation, and substrate targeting for degradation. In this article, we compare and contrast bacterial proteasomes with their archaeal and eukaryotic counterparts, and we discuss recent advances in our understanding of how bacterial proteasomes function to influence microbial physiology.
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Affiliation(s)
| | - K Heran Darwin
- Department of Microbiology, New York University School of Medicine, New York, NY 10016;
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2
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Abstract
This chapter describes the identification of the first prokaryotic ubiquitin-like protein modifier, Pup, which covalently attaches to proteins to target them for destruction by a bacterial proteasome in a manner akin to ubiquitin in eukaryotes. Despite using a proteasome as the end point for proteolysis, Pup and ubiquitin differ in sequence, structure and method of activation and conjugation to protein substrates. Pup is so far the only known posttranslational protein modifier in prokaryotes and its discovery opens the door to the possibility that others are present not only for proteolysis, but also to regulate protein function or localization. Here, we discuss the putative mechanism of activation and conjugation of Pup (termed "pupylation") to target proteins. In addition, because it is unclear whether or not Pup, like ubiquitin, is recycled or degraded during substrate targeting to the proteasome, we propose methods that may identify Pup deconjugation enzymes ("depupylases"). Finally, we outline future directions for Pup research and anti-tuberculosis drug discovery.
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Lasker K, Förster F, Bohn S, Walzthoeni T, Villa E, Unverdorben P, Beck F, Aebersold R, Sali A, Baumeister W. Molecular architecture of the 26S proteasome holocomplex determined by an integrative approach. Proc Natl Acad Sci U S A 2012; 109:1380-7. [PMID: 22307589 PMCID: PMC3277140 DOI: 10.1073/pnas.1120559109] [Citation(s) in RCA: 376] [Impact Index Per Article: 31.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The 26S proteasome is at the executive end of the ubiquitin-proteasome pathway for the controlled degradation of intracellular proteins. While the structure of its 20S core particle (CP) has been determined by X-ray crystallography, the structure of the 19S regulatory particle (RP), which recruits substrates, unfolds them, and translocates them to the CP for degradation, has remained elusive. Here, we describe the molecular architecture of the 26S holocomplex determined by an integrative approach based on data from cryoelectron microscopy, X-ray crystallography, residue-specific chemical cross-linking, and several proteomics techniques. The "lid" of the RP (consisting of Rpn3/5/6/7/8/9/11/12) is organized in a modular fashion. Rpn3/5/6/7/9/12 form a horseshoe-shaped heterohexamer, which connects to the CP and roofs the AAA-ATPase module, positioning the Rpn8/Rpn11 heterodimer close to its mouth. Rpn2 is rigid, supporting the lid, while Rpn1 is conformationally variable, positioned at the periphery of the ATPase ring. The ubiquitin receptors Rpn10 and Rpn13 are located in the distal part of the RP, indicating that they were recruited to the complex late in its evolution. The modular structure of the 26S proteasome provides insights into the sequence of events prior to the degradation of ubiquitylated substrates.
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Affiliation(s)
- Keren Lasker
- Department of Bioengineering and Therapeutic Sciences, Department of Pharmaceutical Chemistry, and California Institute of Quantitative Biosciences, 1700 4th Street, University of California, San Francisco, CA 94158
- Blavatnik School of Computer Science, Raymond and Beverly Sackler Faculty of Exact Sciences, Tel Aviv University, Tel Aviv 69978, Israel
| | - Friedrich Förster
- Department of Molecular Structural Biology, Max-Planck-Institute of Biochemistry, Am Klopferspitz 18, 82152 Martinsried, Germany
| | - Stefan Bohn
- Department of Molecular Structural Biology, Max-Planck-Institute of Biochemistry, Am Klopferspitz 18, 82152 Martinsried, Germany
| | - Thomas Walzthoeni
- Department of Biology, Institute of Molecular Systems Biology, Eidgenössische, Technische Hochschule, 8093 Zürich, Switzerland
- PhD Program in Molecular Life Sciences, University of Zurich/ETH Zurich, Winterthurerstrasse 190, 8057 Zürich, Switzerland; and
| | - Elizabeth Villa
- Department of Molecular Structural Biology, Max-Planck-Institute of Biochemistry, Am Klopferspitz 18, 82152 Martinsried, Germany
| | - Pia Unverdorben
- Department of Molecular Structural Biology, Max-Planck-Institute of Biochemistry, Am Klopferspitz 18, 82152 Martinsried, Germany
| | - Florian Beck
- Department of Molecular Structural Biology, Max-Planck-Institute of Biochemistry, Am Klopferspitz 18, 82152 Martinsried, Germany
| | - Ruedi Aebersold
- Department of Biology, Institute of Molecular Systems Biology, Eidgenössische, Technische Hochschule, 8093 Zürich, Switzerland
- Faculty of Science, University of Zürich, 8093 Zürich, Switzerland
| | - Andrej Sali
- Department of Bioengineering and Therapeutic Sciences, Department of Pharmaceutical Chemistry, and California Institute of Quantitative Biosciences, 1700 4th Street, University of California, San Francisco, CA 94158
| | - Wolfgang Baumeister
- Department of Molecular Structural Biology, Max-Planck-Institute of Biochemistry, Am Klopferspitz 18, 82152 Martinsried, Germany
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Localization of the proteasomal ubiquitin receptors Rpn10 and Rpn13 by electron cryomicroscopy. Proc Natl Acad Sci U S A 2012; 109:1479-84. [PMID: 22215586 DOI: 10.1073/pnas.1119394109] [Citation(s) in RCA: 101] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Two canonical subunits of the 26S proteasome, Rpn10 and Rpn13, function as ubiquitin (Ub) receptors. The mutual arrangement of these subunits--and all other non-ATPase subunits--in the regulatory particle is unknown. Using electron cryomicroscopy, we calculated difference maps between wild-type 26S proteasome from Saccharomyces cerevisiae and deletion mutants (rpn10Δ, rpn13Δ, and rpn10Δrpn13Δ). These maps allowed us to localize the two Ub receptors unambiguously. Rpn10 and Rpn13 mapped to the apical part of the 26S proteasome, above the N-terminal coiled coils of the AAA-ATPase heterodimers Rpt4/Rpt5 and Rpt1/Rpt2, respectively. On the basis of the mutual positions of Rpn10 and Rpn13, we propose a model for polyubiquitin binding to the 26S proteasome.
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The mycobacterial Mpa-proteasome unfolds and degrades pupylated substrates by engaging Pup's N-terminus. EMBO J 2010; 29:1262-71. [PMID: 20203624 DOI: 10.1038/emboj.2010.23] [Citation(s) in RCA: 94] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2009] [Accepted: 02/03/2010] [Indexed: 01/07/2023] Open
Abstract
Mycobacterium tuberculosis, along with other actinobacteria, harbours proteasomes in addition to members of the general bacterial repertoire of degradation complexes. In analogy to ubiquitination in eukaryotes, substrates are tagged for proteasomal degradation with prokaryotic ubiquitin-like protein (Pup) that is recognized by the N-terminal coiled-coil domain of the ATPase Mpa (also called ARC). Here, we reconstitute the entire mycobacterial proteasome degradation system for pupylated substrates and establish its mechanistic features with respect to substrate recruitment, unfolding and degradation. We show that the Mpa-proteasome complex unfolds and degrades Pup-tagged proteins and that this activity requires physical interaction of the ATPase with the proteasome. Furthermore, we establish the N-terminal region of Pup as the structural element required for engagement of pupylated substrates into the Mpa pore. In this process, Mpa pulls on Pup to initiate unfolding of substrate proteins and to drag them toward the proteasome chamber. Unlike the eukaryotic ubiquitin, Pup is not recycled but degraded with the substrate. This assigns a dual function to Pup as both the Mpa recognition element as well as the threading determinant.
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Burns KE, Darwin KH. Pupylation versus ubiquitylation: tagging for proteasome-dependent degradation. Cell Microbiol 2010; 12:424-31. [PMID: 20109157 DOI: 10.1111/j.1462-5822.2010.01447.x] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Prokaryotic ubiquitin-like protein (Pup) is the first identified prokaryotic protein that is functionally analogous to ubiquitin. Despite using the proteasome as the end-point for proteolysis, Pup differs from ubiquitin both biochemically and structurally. We will discuss these differences that have been highlighted by several recent studies. Finally, we will speculate on the possible interactions between the two analogous pathways in pathogen and host.
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Affiliation(s)
- Kristin E Burns
- Department of Microbiology, New York University School of Medicine, New York, NY 10016, USA.
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Wang T, Li H, Lin G, Tang C, Li D, Nathan C, Darwin KH, Li H. Structural insights on the Mycobacterium tuberculosis proteasomal ATPase Mpa. Structure 2010; 17:1377-85. [PMID: 19836337 DOI: 10.1016/j.str.2009.08.010] [Citation(s) in RCA: 60] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2009] [Revised: 08/18/2009] [Accepted: 08/21/2009] [Indexed: 12/16/2022]
Abstract
Proteasome-mediated protein turnover in all domains of life is an energy-dependent process that requires ATPase activity. Mycobacterium tuberculosis (Mtb) was recently shown to possess a ubiquitin-like proteasome pathway that plays an essential role in Mtb resistance to killing by products of host macrophages. Here we report our structural and biochemical investigation of Mpa, the presumptive Mtb proteasomal ATPase. We demonstrate that Mpa binds to the Mtb proteasome in the presence of ATPgammaS, providing the physical evidence that Mpa is the proteasomal ATPase. X-ray crystallographic determination of the conserved interdomain showed a five stranded double beta barrel structure containing a Greek key motif. Structure and mutational analysis indicate a major role of the interdomain for Mpa hexamerization. Our mutational and functional studies further suggest that the central channel in the Mpa hexamer is involved in protein substrate translocation and degradation. These studies provide insights into how a bacterial proteasomal ATPase interacts with and facilitates protein degradation by the proteasome.
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Affiliation(s)
- Tao Wang
- Biology Department, Brookhaven National Laboratory, Upton, NY 11973-5000, USA
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Imkamp F, Rosenberger T, Striebel F, Keller PM, Amstutz B, Sander P, Weber-Ban E. Deletion of dop in Mycobacterium smegmatis abolishes pupylation of protein substrates in vivo. Mol Microbiol 2009; 75:744-54. [PMID: 20025664 DOI: 10.1111/j.1365-2958.2009.07013.x] [Citation(s) in RCA: 61] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Abstract
Proteasome-bearing bacteria make use of a ubiquitin-like modification pathway to target proteins for proteasomal turnover. In a process termed pupylation, proteasomal substrates are covalently modified with the small protein Pup that serves as a degradation signal. Pup is attached to substrate proteins by action of PafA. Prior to its attachment, Pup needs to undergo deamidation at its C-terminal residue, converting glutamine to glutamate. This step is catalysed in vitro by Dop. In order to characterize Dop activity in vivo, we generated a dop deletion mutant in Mycobacterium smegmatis. In the Deltadop strain, pupylation is severely impaired and the steady-state levels of two known proteasomal substrates are drastically increased. Pupylation can be re-established by complementing the mutant with either DopWt or a Pup variant carrying a glutamate at its ultimate C-terminal position (PupGGE). Our data show that Pup is deamidated by Dop in vivo and that likely Dop alone is responsible for this activity. Furthermore, we demonstrate that a putative N-terminal ATP-binding motif is crucial for catalysis, as a single point mutation (E10A) in this motif abolishes Dop activity both in vivo and in vitro.
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Affiliation(s)
- Frank Imkamp
- ETH Zurich, Institute of Molecular Biology & Biophysics, Zurich, Switzerland
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Sutter M, Striebel F, Damberger FF, Allain FHT, Weber-Ban E. A distinct structural region of the prokaryotic ubiquitin-like protein (Pup) is recognized by the N-terminal domain of the proteasomal ATPase Mpa. FEBS Lett 2009; 583:3151-7. [PMID: 19761766 DOI: 10.1016/j.febslet.2009.09.020] [Citation(s) in RCA: 62] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2009] [Revised: 09/04/2009] [Accepted: 09/08/2009] [Indexed: 10/20/2022]
Abstract
The mycobacterial ubiquitin-like protein Pup is coupled to proteins, thereby rendering them as substrates for proteasome-mediated degradation. The Pup-tagged proteins are recruited by the proteasomal ATPase Mpa (also called ARC). Using a combination of biochemical and NMR methods, we characterize the structural determinants of Pup and its interaction with Mpa, demonstrating that Pup adopts a range of extended conformations with a short helical stretch in its C-terminal portion. We show that the N-terminal coiled-coil domain of Mpa makes extensive contacts along the central region of Pup leaving its N-terminus unconstrained and available for other functional interactions.
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Affiliation(s)
- Markus Sutter
- ETH Zurich, Institute of Molecular Biology and Biophysics, Zurich, Switzerland
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Structure and Activity of the N-Terminal Substrate Recognition Domains in Proteasomal ATPases. Mol Cell 2009; 34:580-90. [DOI: 10.1016/j.molcel.2009.04.030] [Citation(s) in RCA: 106] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2008] [Revised: 04/06/2009] [Accepted: 04/23/2009] [Indexed: 11/17/2022]
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Darwin KH. Prokaryotic ubiquitin-like protein (Pup), proteasomes and pathogenesis. Nat Rev Microbiol 2009; 7:485-91. [PMID: 19483713 DOI: 10.1038/nrmicro2148] [Citation(s) in RCA: 76] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
Proteasomes are ATP-dependent, multisubunit proteases that are found in all eukaryotes and archaea and some bacteria. In eukaryotes, the small protein ubiquitin is covalently attached in a post-translational manner to proteins that are targeted for proteasomal degradation. Despite the presence of proteasomes in many prokaryotes, ubiquitin or other post-translational protein modifiers were presumed to be absent from these organisms. Recently a prokaryotic ubiquitin-like protein, Pup, was found to target proteins for proteolysis by the Mycobacterium tuberculosis proteasome. The discovery of this ubiquitin-like modifier opens up the possibility that other bacteria may also have small post-translational protein tagging systems, with the ability to affect cellular processes.
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Affiliation(s)
- K Heran Darwin
- Department of Microbiology, New York University School of Medicine, 550 First Avenue MSB 236, New York, New York 10016, USA.
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Bacterial ubiquitin-like modifier Pup is deamidated and conjugated to substrates by distinct but homologous enzymes. Nat Struct Mol Biol 2009; 16:647-51. [PMID: 19448618 DOI: 10.1038/nsmb.1597] [Citation(s) in RCA: 159] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2009] [Accepted: 04/02/2009] [Indexed: 11/08/2022]
Abstract
In analogy to ubiquitin in eukaryotes, the bacterial protein Pup is attached to lysine residues of substrate proteins, thereby targeting them for proteasomal degradation. It has been proposed that, before its attachment, Pup is modified by deamidation of its C-terminal glutamine to glutamate. Here we have identified Dop (locus tag Rv2112) as the specific deamidase of Pup in Mycobacterium tuberculosis. Deamidation requires ATP as a cofactor but not its hydrolysis. Furthermore, we provide experimental evidence that PafA (locus tag Rv2097) ligates deamidated Pup to the proteasomal substrate proteins FabD and PanB. This formation of an isopeptide bond requires hydrolysis of ATP to ADP, suggesting that deamidated Pup is activated for conjugation via phosphorylation of its C-terminal glutamate. By combining these enzymes, we have reconstituted the complete bacterial ubiquitin-like modification pathway in vitro, consisting of deamidation and ligation steps catalyzed by Pup deamidase (Dop) and Pup ligase (PafA).
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Hartmann C, Chami M, Zachariae U, de Groot BL, Engel A, Grütter MG. Vacuolar protein sorting: two different functional states of the AAA-ATPase Vps4p. J Mol Biol 2008; 377:352-63. [PMID: 18272179 DOI: 10.1016/j.jmb.2008.01.010] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2007] [Revised: 12/19/2007] [Accepted: 01/04/2008] [Indexed: 10/22/2022]
Abstract
The vacuolar protein sorting (Vps) pathway, in which Vps4 class I AAA-ATPases play a central role, regulates growth factor receptors, immune response, and developmental signaling, and participates in tumor suppression, apoptosis, and retrovirus budding. We present the first atomic structure of the nucleotide-free yeast His(6)DeltaNVps4p dimer and its AMPPNP (5'-adenylyl-beta,gamma-imidodiphosphate)-bound tetradecamer, derived from a cryo electron microscopy map. Vps4p dimers form two distinct heptameric rings and accommodate AAA cassettes in a head-to-head--not in a head-to-tail-fashion as in class II AAA-ATPases. Our model suggests a mechanism for disassembling ESCRT (endosomal sorting complex required for transport) complexes by movements of substrate-binding domains located at the periphery of the tetradecamer during ATP hydrolysis in one ring, followed by translocation through the central pore and ATP hydrolysis in the second ring.
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Affiliation(s)
- Claudia Hartmann
- Institute of Biochemistry, University of Zürich, Winterthurer Strasse 190, 8057 Zürich, Switzerland
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De Mot R. Actinomycete-like proteasomes in a Gram-negative bacterium. Trends Microbiol 2007; 15:335-8. [PMID: 17587582 DOI: 10.1016/j.tim.2007.06.002] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2007] [Revised: 05/22/2007] [Accepted: 06/11/2007] [Indexed: 12/23/2022]
Abstract
Cultivation-independent proteogenomic exploration of mine-drainage biofilm has revealed proteasomes in Gram-negative bacteria of the Nitrospirae phylum (Leptospirillum group II) dominating this acidophilic community. Most probably, the proteasome genes were acquired from actinobacteria, the only eubacteria previously known to contain proteasomes. In addition, this study shows that the proteasome and the evolutionarily related ATP-dependent protease HslVU (also known as ClpQY) are not mutually exclusive in prokaryotes.
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Affiliation(s)
- René De Mot
- Centre of Microbial and Plant Genetics, Department of Microbial and Molecular Systems, Faculty of Bioscience Engineering, Katholieke Universiteit Leuven, B-3001 Heverlee-Leuven, Belgium.
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De Mot R, Schoofs G, Nagy I. Proteome analysis of Streptomyces coelicolor mutants affected in the proteasome system reveals changes in stress-responsive proteins. Arch Microbiol 2007; 188:257-71. [PMID: 17486317 DOI: 10.1007/s00203-007-0243-8] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2006] [Revised: 02/19/2007] [Accepted: 04/02/2007] [Indexed: 12/17/2022]
Abstract
Prokaryotic 20S proteasomes are confined to archaebacteria and actinomycetes. Bacterial targets of this compartmentalized multi-subunit protease have not yet been identified and its physiological function in prokaryotes remains unknown. In this study, intracellular and extracellular proteomes of Streptomyces coelicolor A3(2) mutants affected in the structural genes of the 20S proteasome, in the gene encoding the presumed proteasome-accessory AAA ATPase ARC, or in two putative proteasome-associated actinomycete-specific genes (sco1646, sco1647) were analysed, revealing modified patterns of stress-responsive proteins. In addition, the extracellular protease profile of the sco1647 mutant was significantly altered. The most prominent change, common to the four mutants, was a strongly increased level of the non-heme chloroperoxidase SCO0465, coinciding with an increased resistance to cumene hydroperoxide.
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Affiliation(s)
- René De Mot
- Centre of Microbial and Plant Genetics, Department of Microbial and Molecular Systems, Faculty of Bioscience Engineering, Katholieke Universiteit Leuven, Kasteelpark Arenberg 20, 3001 Leuven, Belgium.
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Lin G, Hu G, Tsu C, Kunes YZ, Li H, Dick L, Parsons T, Li P, Chen Z, Zwickl P, Weich N, Nathan C. Mycobacterium tuberculosis prcBA genes encode a gated proteasome with broad oligopeptide specificity. Mol Microbiol 2006; 59:1405-16. [PMID: 16468985 DOI: 10.1111/j.1365-2958.2005.05035.x] [Citation(s) in RCA: 94] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Genes predicted to be associated with the putative proteasome of Mycobacterium tuberculosis (Mtb) play a critical role in defence of the bacillus against nitrosative stress. However, proteasomes are uncommon in eubacteria and it remains to be established whether Mtb's prcBA genes in fact encode a proteasome. We found that coexpression of recombinant PrcB and PrcA in Escherichia coli over a prolonged period at 37 degrees C allowed formation of an alpha(7)beta(7)beta(7)alpha(7), 750 kDa cylindrical stack of four rings in which all 14 beta-subunits were proteolytically processed to expose the active site threonine. In contrast to another Actinomycete, Rhodococcus erythropolis, Mtb's beta-chain propeptide was not required for particle assembly. Peptidolytic activity of the 750 kDa particle towards a hydrophobic oligopeptide was nearly two orders of magnitude less than that of the Rhodococcus 20S proteasome, and unlike eukaryotic and archaeal proteasomes, activity of the Mtb 750 kDa particle could not be stimulated by SDS, Mg(2+) or Ca(2+). Electron microscopy revealed what appeared to be obstructed alpha-rings in the Mtb 750 kDa particle. Deletion of the N-terminal octapeptide from Mtb's alpha-chain led to disappearance of the apparent obstruction and a marked increase of peptidolytic activity. Unlike proteasomes isolated from other Actinomycetes, the open-gate Mtb mutant 750 kDa particle cleaved oligopeptides not only after hydrophobic residues but also after basic, acidic and small, neutral amino acids. Thus, Mtb encodes a broadly active, gated proteasome that may work in concert with an endogenous activator.
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Affiliation(s)
- Gang Lin
- Department of Microbiology and Immunology, Weill Medical College of Cornell University, 1300 York Avenue, New York, NY 10021, USA
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Darwin KH, Lin G, Chen Z, Li H, Nathan CF. Characterization of a Mycobacterium tuberculosis proteasomal ATPase homologue. Mol Microbiol 2005; 55:561-71. [PMID: 15659170 DOI: 10.1111/j.1365-2958.2004.04403.x] [Citation(s) in RCA: 102] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
A screen for Mycobacterium tuberculosis (Mtb) mutants sensitive to reactive nitrogen intermediates identified transposon insertions in the presumptive proteasomal ATPase gene mpa (mycobacterium proteasome ATPase; Rv2115c). mpa mutants are attenuated in both wild type and nitric oxide synthase 2 deficient mice. In this work, we show that attenuation of mpa mutants is severe, and that Mpa is an ATPase associated with various cellular activities (AAA) ATPase that forms hexameric rings resembling the eukaryotic complex p97/valosin-containing protein (VCP). Point mutations in the conserved Walker box ATPase motifs of Mpa greatly reduced or abolished ATPase activity in vitro and abrogated protection of Mtb against acidified nitrite. A mutant Mpa protein missing only its last two amino acids retained ATPase activity, yet failed to protect Mtb against nitrite. The corresponding strain was attenuated in mice. Thus, Mpa is an ATPase whose enzymatic activity is necessary but not sufficient to protect against reactive nitrogen intermediates.
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Affiliation(s)
- K Heran Darwin
- Department of Microbiology and Immunology, Weill Medical College of Cornell University, 1300 York Avenue, New York, NY 10021, USA.
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