Proteasomes in the Methanogenic Archea

9513863 Ferry蛋白酶体普遍存在于真核生物结构域中，它们至少有三种不同的内肽酶活性，催化疏水、碱性和酸性氨基酸残基的羧基上的肽键的水解性。有人认为，真核蛋白酶体是一个更大的复合体中的“催化核心”，它在依赖于ATP的过程中降解泛素标记的蛋白质。早期对细菌和古生界物种的调查表明，热浆物种是唯一含有蛋白酶体的原核生物。最近关于产甲烷微生物的系统发育和生理多样性物种的蛋白酶体的文献表明，蛋白酶体在原核生物中比以前所知的更广泛。这项工作的总体重点是对这一大群厌氧微生物中蛋白质周转的生理、生化和分子生物学进行调查。本项目的具体目标是：(1)对嗜热甲烷链球菌蛋白酶体进行生化表征，(2)通过确定影响蛋白酶体合成和活性调节的因素，以及确定蛋白酶体和泛素在蛋白质周转中的作用来阐述其生理功能。这些结果有望：(1)扩大泛素和蛋白酶体在自然界中的进化、机制和功能的基础知识；(2)更广泛地了解嗜热支原体和产甲烷古细菌的生物化学、遗传学和生理学；(3)有助于进一步确定古生界和真核生物之间的进化关系。%蛋白酶体是真核细胞中介导蛋白质分解的复杂酶聚体。最近，在原核生物的两大类群之一的古细菌中发现了蛋白酶体。在这个项目中，我们将研究产甲烷细菌嗜热甲烷单胞菌的蛋白酶体的分子结构。此外，还将研究这些结构的功能。这些结果将提供关于主要有机体群体之间进化关系的证据，以及关于考古细菌如何调控其蛋白质降解的信息，这是一个尚未探索的领域。***

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. ***