1
|
Marshall RS, Vierstra RD. Dynamic Regulation of the 26S Proteasome: From Synthesis to Degradation. Front Mol Biosci 2019; 6:40. [PMID: 31231659 PMCID: PMC6568242 DOI: 10.3389/fmolb.2019.00040] [Citation(s) in RCA: 138] [Impact Index Per Article: 27.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2019] [Accepted: 05/09/2019] [Indexed: 01/12/2023] Open
Abstract
All eukaryotes rely on selective proteolysis to control the abundance of key regulatory proteins and maintain a healthy and properly functioning proteome. Most of this turnover is catalyzed by the 26S proteasome, an intricate, multi-subunit proteolytic machine. Proteasomes recognize and degrade proteins first marked with one or more chains of poly-ubiquitin, the addition of which is actuated by hundreds of ligases that individually identify appropriate substrates for ubiquitylation. Subsequent proteasomal digestion is essential and influences a myriad of cellular processes in species as diverse as plants, fungi and humans. Importantly, dysfunction of 26S proteasomes is associated with numerous human pathologies and profoundly impacts crop performance, thus making an understanding of proteasome dynamics critically relevant to almost all facets of human health and nutrition. Given this widespread significance, it is not surprising that sophisticated mechanisms have evolved to tightly regulate 26S proteasome assembly, abundance and activity in response to demand, organismal development and stress. These include controls on transcription and chaperone-mediated assembly, influences on proteasome localization and activity by an assortment of binding proteins and post-translational modifications, and ultimately the removal of excess or damaged particles via autophagy. Intriguingly, the autophagic clearance of damaged 26S proteasomes first involves their modification with ubiquitin, thus connecting ubiquitylation and autophagy as key regulatory events in proteasome quality control. This turnover is also influenced by two distinct biomolecular condensates that coalesce in the cytoplasm, one attracting damaged proteasomes for autophagy, and the other reversibly storing proteasomes during carbon starvation to protect them from autophagic clearance. In this review, we describe the current state of knowledge regarding the dynamic regulation of 26S proteasomes at all stages of their life cycle, illustrating how protein degradation through this proteolytic machine is tightly controlled to ensure optimal growth, development and longevity.
Collapse
Affiliation(s)
- Richard S Marshall
- Department of Biology, Washington University in St. Louis, St. Louis, MO, United States
| | - Richard D Vierstra
- Department of Biology, Washington University in St. Louis, St. Louis, MO, United States
| |
Collapse
|
2
|
Structural insights on the dynamics of proteasome formation. Biophys Rev 2017; 10:597-604. [PMID: 29243089 DOI: 10.1007/s12551-017-0381-4] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2017] [Accepted: 11/27/2017] [Indexed: 12/28/2022] Open
Abstract
Molecular organization in biological systems comprises elaborately programmed processes involving metastable complex formation of biomolecules. This is exemplified by the formation of the proteasome, which is one of the largest and most complicated biological supramolecular complexes. This biomolecular machinery comprises approximately 70 subunits, including structurally homologous, but functionally distinct, ones, thereby exerting versatile proteolytic functions. In eukaryotes, proteasome formation is non-autonomous and is assisted by assembly chaperones, which transiently associate with assembly intermediates, operating as molecular matchmakers and checkpoints for the correct assembly of proteasome subunits. Accumulated data also suggest that eukaryotic proteasome formation involves scrap-and-build mechanisms. However, unlike the eukaryotic proteasome subunits, the archaeal subunits show little structural divergence and spontaneously assemble into functional machinery. Nevertheless, the archaeal genomes encode homologs of eukaryotic proteasome assembly chaperones. Recent structural and functional studies of these proteins have advanced our understanding of the evolution of molecular mechanisms involved in proteasome biogenesis. This knowledge, in turn, provides a guiding principle in designing molecular machineries using protein engineering approaches and de novo synthesis of artificial molecular systems.
Collapse
|
3
|
Budenholzer L, Cheng CL, Li Y, Hochstrasser M. Proteasome Structure and Assembly. J Mol Biol 2017; 429:3500-3524. [PMID: 28583440 DOI: 10.1016/j.jmb.2017.05.027] [Citation(s) in RCA: 224] [Impact Index Per Article: 32.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2017] [Revised: 05/22/2017] [Accepted: 05/30/2017] [Indexed: 10/19/2022]
Abstract
The eukaryotic 26S proteasome is a large multisubunit complex that degrades the majority of proteins in the cell under normal conditions. The 26S proteasome can be divided into two subcomplexes: the 19S regulatory particle and the 20S core particle. Most substrates are first covalently modified by ubiquitin, which then directs them to the proteasome. The function of the regulatory particle is to recognize, unfold, deubiquitylate, and translocate substrates into the core particle, which contains the proteolytic sites of the proteasome. Given the abundance and subunit complexity of the proteasome, the assembly of this ~2.5MDa complex must be carefully orchestrated to ensure its correct formation. In recent years, significant progress has been made in the understanding of proteasome assembly, structure, and function. Technical advances in cryo-electron microscopy have resulted in a series of atomic cryo-electron microscopy structures of both human and yeast 26S proteasomes. These structures have illuminated new intricacies and dynamics of the proteasome. In this review, we focus on the mechanisms of proteasome assembly, particularly in light of recent structural information.
Collapse
Affiliation(s)
- Lauren Budenholzer
- Department of Molecular Biophysics & Biochemistry, Yale University, 266 Whitney Avenue, New Haven, CT 06520, USA
| | - Chin Leng Cheng
- Department of Molecular Biophysics & Biochemistry, Yale University, 266 Whitney Avenue, New Haven, CT 06520, USA
| | - Yanjie Li
- Department of Molecular Biophysics & Biochemistry, Yale University, 266 Whitney Avenue, New Haven, CT 06520, USA
| | - Mark Hochstrasser
- Department of Molecular Biophysics & Biochemistry, Yale University, 266 Whitney Avenue, New Haven, CT 06520, USA.
| |
Collapse
|
4
|
Alpha-ring Independent Assembly of the 20S Proteasome. Sci Rep 2015; 5:13130. [PMID: 26286114 PMCID: PMC4541365 DOI: 10.1038/srep13130] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2015] [Accepted: 07/20/2015] [Indexed: 12/17/2022] Open
Abstract
Archaeal proteasomes share many features with their eukaryotic counterparts and serve as important models for assembly. Proteasomes are also found in certain bacterial lineages yet their assembly mechanism is thought to be fundamentally different. Here we investigate α-ring formation using recombinant proteasomes from the archaeon Methanococcus maripaludis. Through an engineered disulfide cross-linking strategy, we demonstrate that double α-rings are structurally analogous to half-proteasomes and can form independently of single α-rings. More importantly, via targeted mutagenesis, we show that single α-rings are not required for the efficient assembly of 20S proteasomes. Our data support updating the currently held "α-ring first" view of assembly, initially proposed in studies of archaeal proteasomes, and present a way to reconcile the seemingly separate bacterial assembly mechanism with the rest of the proteasome realm. We suggest that a common assembly network underpins the absolutely conserved architecture of proteasomes across all domains of life.
Collapse
|
5
|
Role of the Ubiquitin-Proteasome Systems in the Biology and Virulence of Protozoan Parasites. BIOMED RESEARCH INTERNATIONAL 2015; 2015:141526. [PMID: 26090380 PMCID: PMC4452248 DOI: 10.1155/2015/141526] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/01/2014] [Accepted: 10/06/2014] [Indexed: 11/18/2022]
Abstract
In eukaryotic cells, proteasomes perform crucial roles in many cellular pathways by degrading proteins to enforce quality control and regulate many cellular processes such as cell cycle progression, signal transduction, cell death, immune responses, metabolism, protein-quality control, and development. The catalytic heart of these complexes, the 20S proteasome, is highly conserved in bacteria, yeast, and humans. However, until a few years ago, the role of proteasomes in parasite biology was completely unknown. Here, we summarize findings about the role of proteasomes in protozoan parasites biology and virulence. Several reports have confirmed the role of proteasomes in parasite biological processes such as cell differentiation, cell cycle, proliferation, and encystation. Proliferation and cell differentiation are key steps in host colonization. Considering the importance of proteasomes in both processes in many different parasites such as Trypanosoma, Leishmania, Toxoplasma, and Entamoeba, parasite proteasomes might serve as virulence factors. Several pieces of evidence strongly suggest that the ubiquitin-proteasome pathway is also a viable parasitic therapeutic target. Research in recent years has shown that the proteasome is a valid drug target for sleeping sickness and malaria. Then, proteasomes are a key organelle in parasite biology and virulence and appear to be an attractive new chemotherapeutic target.
Collapse
|
6
|
Kunjappu MJ, Hochstrasser M. Assembly of the 20S proteasome. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2013; 1843:2-12. [PMID: 23507199 DOI: 10.1016/j.bbamcr.2013.03.008] [Citation(s) in RCA: 67] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/25/2012] [Revised: 03/02/2013] [Accepted: 03/05/2013] [Indexed: 10/27/2022]
Abstract
The proteasome is a cellular protease responsible for the selective degradation of the majority of the intracellular proteome. It recognizes, unfolds, and cleaves proteins that are destined for removal, usually by prior attachment to polymers of ubiquitin. This macromolecular machine is composed of two subcomplexes, the 19S regulatory particle (RP) and the 20S core particle (CP), which together contain at least 33 different and precisely positioned subunits. How these subunits assemble into functional complexes is an area of active exploration. Here we describe the current status of studies on the assembly of the 20S proteasome (CP). The 28-subunit CP is found in all three domains of life and its cylindrical stack of four heptameric rings is well conserved. Though several CP subunits possess self-assembly properties, a consistent theme in recent years has been the need for dedicated assembly chaperones that promote on-pathway assembly. To date, a minimum of three accessory factors have been implicated in aiding the construction of the 20S proteasome. These chaperones interact with different assembling proteasomal precursors and usher subunits into specific slots in the growing structure. This review will focus largely on chaperone-dependent CP assembly and its regulation. This article is part of a Special Issue entitled: Ubiquitin-Proteasome System. Guest Editors: Thomas Sommer and Dieter H. Wolf.
Collapse
Affiliation(s)
- Mary J Kunjappu
- Department of Molecular, Cellular and Developmental Biology, Yale University, 266 Whitney Avenue P.O. Box 208114, New Haven, CT 06520-8114, USA
| | | |
Collapse
|
7
|
Abstract
The eukaryotic ubiquitin-proteasome system is responsible for most aspects of regulatory and quality-control protein degradation in cells. Its substrates, which are usually modified by polymers of ubiquitin, are ultimately degraded by the 26S proteasome. This 2.6-MDa protein complex is separated into a barrel-shaped proteolytic 20S core particle (CP) of 28 subunits capped on one or both ends by a 19S regulatory particle (RP) comprising at least 19 subunits. The RP coordinates substrate recognition, removal of substrate polyubiquitin chains, and substrate unfolding and translocation into the CP for degradation. Although many atomic structures of the CP have been determined, the RP has resisted high-resolution analysis. Recently, however, a combination of cryo-electron microscopy, biochemical analysis, and crystal structure determination of several RP subunits has yielded a near-atomic-resolution view of much of the complex. Major new insights into chaperone-assisted proteasome assembly have also recently emerged. Here we review these novel findings.
Collapse
Affiliation(s)
- Robert J Tomko
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, Connecticut 06520, USA.
| | | |
Collapse
|
8
|
Dielen AS, Sassaki FT, Walter J, Michon T, Ménard G, Pagny G, Krause-Sakate R, Maia IDG, Badaoui S, Le Gall O, Candresse T, German-Retana S. The 20S proteasome α5 subunit of Arabidopsis thaliana carries an RNase activity and interacts in planta with the lettuce mosaic potyvirus HcPro protein. MOLECULAR PLANT PATHOLOGY 2011; 12:137-50. [PMID: 21199564 PMCID: PMC6640220 DOI: 10.1111/j.1364-3703.2010.00654.x] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/07/2023]
Abstract
In plants, the ubiquitin/26S proteasome system (UPS) plays a central role in protein degradation and is involved in many steps of defence mechanisms, regardless of the types of pathogen targeted. In addition to its proteolytic activities, the UPS ribonuclease (RNase) activity, previously detected in 20S proteasome preparations from cauliflower and sunflower (Helianthus annuus), has been shown to specifically target plant viral RNAs in vitro. In this study, we show that recombinant Arabidopsis thaliana proteasomal α(5) subunit expressed in Escherichia coli harbours an RNase activity that degrades Tobacco mosaic virus (TMV, Tobamovirus)- and Lettuce mosaic virus (LMV, Potyvirus)-derived RNAs in vitro. The analysis of mutated forms of the α(5) subunit demonstrated that mutation of a glutamic acid at position 110 affects RNase activity. Furthermore, it was demonstrated, using a bimolecular fluorescence complement assay, that the multifunctional helper component proteinase (HcPro) of LMV, already known to interfere with the 20S proteasome RNase activity in vitro, can interact in vivo with the recombinant α(5) subunit. Further experiments demonstrated that, in LMV-infected lettuce cells, α(5) is partially relocalized to HcPro-containing infection-specific inclusions. Susceptibility analyses of Arabidopsis mutants, knocked out for each At-PAE gene encoding α(5) , showed that one (KO-pae1) of the two mutants exhibited a significantly increased susceptibility to LMV infection. Taken together, these results extend to A. thaliana α(5) the range of HcPro-interacting proteasomal subunits, and suggest that HcPro may modulate its associated RNase activity which may contribute to an antiviral response.
Collapse
Affiliation(s)
- Anne-Sophie Dielen
- Interactions Plante-Virus, UMR GDPP 1090, INRA Université de Bordeaux 2, BP 81, F-33883 Villenave d'Ornon Cedex, France
| | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
9
|
Assembly, structure, and function of the 26S proteasome. Trends Cell Biol 2010; 20:391-401. [PMID: 20427185 DOI: 10.1016/j.tcb.2010.03.007] [Citation(s) in RCA: 187] [Impact Index Per Article: 13.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/25/2009] [Revised: 03/30/2010] [Accepted: 03/31/2010] [Indexed: 01/15/2023]
Abstract
The 26S proteasome is a large multiprotein complex involved in the regulated degradation of ubiquitinated proteins in the cell. The 26S proteasome has been shown to control an increasing number of essential biochemical mechanisms of the cellular lifecycle including DNA synthesis, repair, transcription, translation, and cell signal transduction. Concurrently, it is increasingly seen that malfunction of the ubiquitin proteasome system contributes to the pathogenesis of disease. The recent identification of four molecular chaperones, in addition to five previously identified chaperones, have provided mechanistic insight into how this cellular megastructure is assembled in the cell. These data, together with new insights into the structure and function of the proteasome, provide a much better understanding of this complex protease.
Collapse
|
10
|
Reguera RM, Redondo CM, Gutierrez de Prado R, Pérez-Pertejo Y, Balaña-Fouce R. DNA topoisomerase I from parasitic protozoa: A potential target for chemotherapy. ACTA ACUST UNITED AC 2006; 1759:117-31. [PMID: 16757380 DOI: 10.1016/j.bbaexp.2006.03.006] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2006] [Revised: 03/22/2006] [Accepted: 03/30/2006] [Indexed: 11/28/2022]
Abstract
The growing occurrence of drug resistant strains of unicellular prokaryotic parasites, along with insecticide-resistant vectors, are the factors contributing to the increased prevalence of tropical diseases in underdeveloped and developing countries, where they are endemic. Malaria, cryptosporidiosis, African and American trypanosomiasis and leishmaniasis threaten human beings, both for the high mortality rates involved and the economic loss resulting from morbidity. Due to the fact that effective immunoprophylaxis is not available at present; preventive sanitary measures and pharmacological approaches are the only sources to control the undesirable effects of such diseases. Current anti-parasitic chemotherapy is expensive, has undesirable side effects or, in many patients, is only marginally effective. Under this point of view molecular biology techniques and drug discovery must walk together in order to find new targets for chemotherapy intervention. The identification of DNA topoisomerases as a promising drug target is based on the clinical success of camptothecin derivatives as anticancer agents. The recent detection of substantial differences between trypanosome and leishmania DNA topoisomerase IB with respect to their homologues in mammals has provided a new lead in the study of the structural determinants that can be effectively targeted. The present report is an up to date review of the new findings on type IB DNA topoisomerase in unicellular parasites and the role of these enzymes as targets for therapeutic agents.
Collapse
Affiliation(s)
- R M Reguera
- Dpto. Farmacología y Toxicología (INTOXCAL), Universidad de León, Campus de Vegazana s/n, 24071 León, Spain
| | | | | | | | | |
Collapse
|
11
|
Dubessay P, Blaineau C, Bastien P, Tasse L, Van Dijk J, Crobu L, Pagès M. Cell cycle-dependent expression regulation by the proteasome pathway and characterization of the nuclear targeting signal of a Leishmania major Kin-13 kinesin. Mol Microbiol 2006; 59:1162-74. [PMID: 16430691 DOI: 10.1111/j.1365-2958.2005.05013.x] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The LmjF01.0030 gene of Leishmania major Friedlin, annotated as 'MCAK-like', was confirmed as a kinesin with an internally located motor domain and termed LmjKIN13-1. Both the native form of the protein and a green fluorescent protein (GFP)-fused recombinant version were shown to be exclusively intranuclear, and, more specifically, to localize to the spindle and spindle poles. Cell cycle-dependent regulation of the protein levels was demonstrated using synchronized Leishmania cells: LmjKIN13-1 was highly abundant in the G2+M phase and present at very low levels after mitosis. Altogether, these features suggest that this protein participates in mitosis. The construction of systematic deletion mutants allowed the localization of the primary sequence regions responsible for nuclear targeting on the one hand, and for cell cycle-dependent variations on the other hand. A 42-amino-acid region of the carboxy(C)-terminal domain mediates nuclear import and could be defined as an atypical nuclear localization signal. Protein level regulation during the cell cycle was shown to also depend upon the C-terminal domain, where apparently redundant degradation signals are present. Putative degradation signals appear to be present on both sides and inside the nuclear localization signal. Further experiments strongly suggest a role for the ubiquitin/proteasome pathway in this cell cycle-dependent regulation. These data underline the importance of post-translational regulation of protein abundance in this ancestral eukaryote where transcriptional regulation seems to be rare or near absent.
Collapse
Affiliation(s)
- Pascal Dubessay
- UMR5093 CNRS/Université Montpellier I Génome et Biologie Moléculaire des Protozoaires Parasites, Laboratoire de Parasitologie-Mycologie, Faculté de Médecine, 163 Rue Auguste Broussonet, 34090 Montpellier, France
| | | | | | | | | | | | | |
Collapse
|
12
|
Kwon YD, Nagy I, Adams PD, Baumeister W, Jap BK. Crystal structures of the Rhodococcus proteasome with and without its pro-peptides: implications for the role of the pro-peptide in proteasome assembly. J Mol Biol 2004; 335:233-45. [PMID: 14659753 DOI: 10.1016/j.jmb.2003.08.029] [Citation(s) in RCA: 69] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
To understand the role of the pro-peptide in proteasome assembly, we have determined structures of the Rhodococcus proteasome and a mutant form that prevents the autocatalytic removal of its pro-peptides. The structures reveal that the pro-peptide acts as an assembly-promoting factor by linking its own beta-subunit to two adjacent alpha-subunits, thereby providing a molecular explanation for the observed kinetics of proteasome assembly. The Rhodococcus proteasome has been found to have a substantially smaller contact region between alpha-subunits compared to those regions in the proteasomes of Thermoplasma, yeast, and mammalian cells, suggesting that a smaller contact area between alpha-subunits is likely the structural basis for the Rhodococcus alpha-subunits not assembling into alpha-rings when expressed alone. Analysis of all available beta-subunit structures shows that the contact area between beta-subunits within a beta-ring is not sufficient for beta-ring self-assembly without the additional contact provided by the alpha-ring. This appears to be a fail-safe mechanism ensuring that the active sites on the beta-subunits are activated only after proteasome assembly is complete.
Collapse
Affiliation(s)
- Young Do Kwon
- Graduate Group in Comparative Biochemistry, University of California, Berkeley, CA 94720, USA
| | | | | | | | | |
Collapse
|
13
|
Maupin-Furlow JA, Kaczowka SJ, Reuter CJ, Zuobi-Hasona K, Gil MA. Archaeal proteasomes: potential in metabolic engineering. Metab Eng 2003; 5:151-63. [PMID: 12948749 DOI: 10.1016/s1096-7176(03)00030-2] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
Archaea are a valuable source of enzymes for industrial and scientific applications because of their ability to survive extreme conditions including high salt and temperature. Thanks to advances in molecular biology and genetics, archaea are also attractive hosts for metabolic engineering. Understanding how energy-dependent proteases and chaperones function to maintain protein quality control is key to high-level synthesis of recombinant products. In archaea, proteasomes are central players in energy-dependent proteolysis and form elaborate nanocompartments that degrade proteins into oligopeptides by processive hydrolysis. The catalytic core responsible for this proteolytic activity is the 20S proteasome, a barrel-shaped particle with a central channel and axial gates on each end that limit substrate access to a central proteolytic chamber. AAA proteins (ATPases associated with various cellular activities) are likely to play several roles in mediating energy-dependent proteolysis by the proteasome. These include ATP binding/hydrolysis, substrate binding/unfolding, opening of the axial gates, and translocation of substrate into the proteolytic chamber.
Collapse
Affiliation(s)
- Julie A Maupin-Furlow
- Department of Microbiology and Cell Science, University of Florida, Room 1052, Building 981, Gainesville, FL 32611-0700, USA.
| | | | | | | | | |
Collapse
|
14
|
Abstract
Haloferax volcanii, a halophilic archaeon, synthesizes three different proteins (alpha1, alpha2, and beta) which are classified in the 20S proteasome superfamily. The alpha1 and beta proteins alone form active 20S proteasomes; the role of alpha2, however, is not clear. To address this, alpha2 was synthesized with an epitope tag and purified by affinity chromatography from recombinant H. volcanii. The alpha2 protein copurified with alpha1 and beta in a complex with an overall structure and peptide-hydrolyzing activity comparable to those of the previously described alpha1-beta proteasome. Supplementing buffers with 10 mM CaCl(2) stabilized the halophilic proteasomes in the absence of salt and enabled them to be separated by native gel electrophoresis. This facilitated the discovery that wild-type H. volcanii synthesizes more than one type of 20S proteasome. Two 20S proteasomes, the alpha1-beta and alpha1-alpha2-beta proteasomes, were identified during stationary phase. Cross-linking of these enzymes, coupled with available structural information, suggested that the alpha1-beta proteasome was a symmetrical cylinder with alpha1 rings on each end. In contrast, the alpha1-alpha2-beta proteasome appeared to be asymmetrical with homo-oligomeric alpha1 and alpha2 rings positioned on separate ends. Inter-alpha-subunit contacts were only detected when the ratio of alpha1 to alpha2 was perturbed in the cell using recombinant technology. These results support a model that the ratio of alpha proteins may modulate the composition and subunit topology of 20S proteasomes in the cell.
Collapse
Affiliation(s)
- Steven J Kaczowka
- Department of Microbiology and Cell Science, University of Florida, Gainesville, FL 32611-0700, USA
| | | |
Collapse
|
15
|
Zwickl P, Seemüller E, Kapelari B, Baumeister W. The proteasome: a supramolecular assembly designed for controlled proteolysis. ADVANCES IN PROTEIN CHEMISTRY 2002; 59:187-222. [PMID: 11868272 DOI: 10.1016/s0065-3233(01)59006-3] [Citation(s) in RCA: 42] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Affiliation(s)
- P Zwickl
- Department of Molecular Structural Biology, Max-Planck Institute for Biochemistry, Am Klopferspitz 18a, 82152 Martinsried, Germany
| | | | | | | |
Collapse
|
16
|
Abstract
In contrast to our detailed knowledge of prokaryotic proteasomes, we have only a limited understanding of the prokaryotic regulators and their functional interaction with the proteasome. Most probably, we will soon learn more about the molecular structure and the mechanism of action of the prokaryotic regulators. Nevertheless, it still remains to be unravelled which signals or/and modifications transform an endogenous prokaryotic protein into a substrate of the proteasomal degradation machinery.
Collapse
Affiliation(s)
- P Zwickl
- Department of Molecular Structural Biology, Max Planck Institute for Biochemistry, Am Klopferspitz 18a, 82152 Martinsried, Germany
| |
Collapse
|
17
|
Self-Processing of Subunits of the Proteasome. CO- AND POSTTRANSLATIONAL PROTEOLYSIS OF PROTEINS 2002. [DOI: 10.1016/s1874-6047(02)80013-0] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/05/2022]
|
18
|
Wilson HL, Ou MS, Aldrich HC, Maupin-Furlow J. Biochemical and physical properties of the Methanococcus jannaschii 20S proteasome and PAN, a homolog of the ATPase (Rpt) subunits of the eucaryal 26S proteasome. J Bacteriol 2000; 182:1680-92. [PMID: 10692374 PMCID: PMC94466 DOI: 10.1128/jb.182.6.1680-1692.2000] [Citation(s) in RCA: 68] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The 20S proteasome is a self-compartmentalized protease which degrades unfolded polypeptides and has been purified from eucaryotes, gram-positive actinomycetes, and archaea. Energy-dependent complexes, such as the 19S cap of the eucaryal 26S proteasome, are assumed to be responsible for the recognition and/or unfolding of substrate proteins which are then translocated into the central chamber of the 20S proteasome and hydrolyzed to polypeptide products of 3 to 30 residues. All archaeal genomes which have been sequenced are predicted to encode proteins with up to approximately 50% identity to the six ATPase subunits of the 19S cap. In this study, one of these archaeal homologs which has been named PAN for proteasome-activating nucleotidase was characterized from the hyperthermophile Methanococcus jannaschii. In addition, the M. jannaschii 20S proteasome was purified as a 700-kDa complex by in vitro assembly of the alpha and beta subunits and has an unusually high rate of peptide and unfolded-polypeptide hydrolysis at 100 degrees C. The 550-kDa PAN complex was required for CTP- or ATP-dependent degradation of beta-casein by archaeal 20S proteasomes. A 500-kDa complex of PAN(Delta1-73), which has a deletion of residues 1 to 73 of the deduced protein and disrupts the predicted N-terminal coiled-coil, also facilitated this energy-dependent proteolysis. However, this deletion increased the types of nucleotides hydrolyzed to include not only ATP and CTP but also ITP, GTP, TTP, and UTP. The temperature optimum for nucleotide (ATP) hydrolysis was reduced from 80 degrees C for the full-length protein to 65 degrees C for PAN(Delta1-73). Both PAN protein complexes were stable in the absence of ATP and were inhibited by N-ethylmaleimide and p-chloromercuriphenyl-sulfonic acid. Kinetic analysis reveals that the PAN protein has a relatively high V(max) for ATP and CTP hydrolysis of 3.5 and 5.8 micromol of P(i) per min per mg of protein as well as a relatively low affinity for CTP and ATP with K(m) values of 307 and 497 microM compared to other proteins of the AAA family. Based on electron micrographs, PAN and PAN(Delta1-73) apparently associate with the ends of the 20S proteasome cylinder. These results suggest that the M. jannaschii as well as related archaeal 20S proteasomes require a nucleotidase complex such as PAN to mediate the energy-dependent hydrolysis of folded-substrate proteins and that the N-terminal 73 amino acid residues of PAN are not absolutely required for this reaction.
Collapse
Affiliation(s)
- H L Wilson
- Department of Microbiology and Cell Science, University of Florida, Gainesville, Florida 32611-0700, USA
| | | | | | | |
Collapse
|