Proteasomes in the Methanogenic Archea

9513863 Ferry蛋白酶体普遍存在于真核生物结构域中，其中它们具有至少三种不同的内肽酶活性，其催化疏水性、碱性和酸性氨基酸残基的羧基侧上的肽键水解。有人提出，真核生物蛋白酶体是一个更大的复合体中的“催化核心”，在ATP依赖性过程中降解泛素标记的蛋白质。一个早期的调查，从细菌和真菌领域的物种导致的建议，热原体物种是唯一的原核生物含有蛋白酶体。最近的文献中的产甲烷微生物，最大的群体在生物遗传学和生理学上的不同物种的蛋白酶体，表明蛋白酶体是更广泛的原核生物比以前已知的。这项工作的总体重点是研究这一大群厌氧微生物中蛋白质周转的生理学、生物化学和分子生物学。本项目的具体目标是：（1）对嗜热甲烷八叠球菌蛋白酶体进行生物化学表征;（2）通过确定影响蛋白酶体合成和活性的因素，并确定蛋白酶体和泛素在蛋白质周转中的作用，来阐明其生理功能。预期结果将：（1）扩展了对自然界中泛素和蛋白酶体的进化、机制和功能的基础知识，（2）提供了对M.嗜热古菌和产甲烷古菌;（3）有助于进一步确定古菌和真核菌域之间的进化关系。 蛋白酶体是在真核细胞中介导蛋白质分解的复杂酶聚集体。 最近，蛋白酶体已被确定在古细菌，原核生物的两个主要群体之一。 本计画将研究产甲烷菌嗜热甲烷八叠球菌蛋白酶体的分子结构。 此外，还将研究这些结构的功能。 这些结果将提供有关主要生物群体之间进化关系的证据，以及有关古细菌如何调节其蛋白质降解的信息，这是一个未探索的领域。 ***

9513863 Ferry Proteasomes are prevalent in the Eucarya domain where they have at least three distinct endopeptidase activities which catalyze hydrolysis of peptide bonds on the carboxyl side of hydrophobic, basic, and acidic amino acid residues. It is proposed that the eukaryotic proteasome is the "catalytic core" in a larger complex that degrades proteins labeled with ubiquitin in an ATP-dependent process. A earlier survey of species from the Bacteria and Archaea domains led to the suggestion that Thermoplasma species are the only prokaryotes containing proteasomes. Recent documentation of proteasomes in phylogenetically and physiologically diverse species of methanogenic microbes, the largest group in the Archaea, demonstrates that proteasomes are more widespread among prokaryotes than previously known. The overall focus of this work is an investigating into the physiology, biochemistry and molecular biology of protein turnover in this large group of anaerobic microbes. The specific aims of this project are: (1) biochemically characterize the Methanosarcina thermophila proteasome, and (2) address its physiological function by ascertaining the factors influencing the regulation of proteasome synthesis and activity, and determining the roles for the proteasome and ubiquitin in protein turnover. The results are expected to: (1) expand the fundamental knowledge of the evolution, mechanism and function of ubiquitin and proteasomes in all of nature, (2) provide a broader understanding of the biochemistry, genetics and physiology of M. thermophila and the methanogenic Archaea, and (3) help to further define the evolutionary relationships between the Archaea and Eucarya domains. %%% Proteasomes are complex enzyme aggregates that mediate protein breakdown in eukaryotic cells. Recently, proteasomes have been identified in archaebacteria, one of the two major groups of prokaryotes. In this project, the molecular structure of proteasomes from a methane-producing bacterium, Methanosarcina thermophila will be studied. In addition, the function of these structures will be investigated. The results will provide evidence about evolutionary relationships among major groups of organisms as well as information about how archaebacteria regulate degradation of their proteins, an unexplored area. ***