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Biochemistry and Molecular Biology

Identification of Oma1p Protease Sensitive Sites in Subunit 1 of Yeast Cytochrome Oxidase

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Cytochrome c oxidase is the terminal electron acceptor in the electron transport chain in many aerobic organisms. This multi-protein complex can be composed of a varying number of subunits depending on species. In the budding yeast, Saccharomyces cerevisiae, cytochrome c oxidase is made up of 11 subunits, 8 are derived from the nuclear genome and 3 are derived from the mitochondrial genome. To ensure these subunits come together at the correct time and place a family of assembly factors is required. In the case of the mitochondrial DNA encoded subunit 1 there is a linear pathway of biosynthesis where these assembly factors and other structural subunits associate at specific times to regulate specific maturation events. In the absence of some assembly factors subunit 1 is subject to degradation by the protease Oma1p. In yeast, this results in a deficiency in cytochrome c oxidase activity and the inability to grow using substrates requiring intact oxidative phosphorylation. We have performed a mutagenic screen of mitochondrial DNA to identify mutations in the subunit 1 gene that can suppress the oxidative phosphorylation deficient phenotype caused by the absence of the assembly factors, COA2 and SHY1. Through analysis of the COX1 gene we will identify putative regions required for the proteolytic processing of subunit 1 by the Oma1p protease. The information gathered from this research will guide us in identifying putative regions required for cytochrome c oxidase subunit 1 degradation and also provide more information regarding the proteolytic requirements of the Oma1p protease.