Proteasomes in the Methanogenic Archea

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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. ***