Mutational Analysis of the yeast Oxa1 Protein

The inner mitochondrial membrane contains many multi‐subunit complexes involved in processes such as protein insertion, oxidative phosphorylation and proteolysis. Oxa1, an inner mitochondrial membrane protein, is a member of the highly conserved Oxa1/YidC/Alb3 family found throughout eukaryotes and prokaryotes. Oxa1 is responsible for the insertion of nuclear and mitochondrial encoded proteins into the mitochondrial inner membrane from the matrix. Oxa1 exists in a homo‐oligomeric complex believed to be a tetramer. The precise mechanism explaining how Oxa1 functions is not known. Oxa1 null mutants are unable to grow on non‐fermentable carbon sources such as glycerol. This phenotype is observed due to the inability to insert and fully assemble complexes needed to function in oxidative phosphorylation. BLASTp analyses indicate the first transmembrane region to be highly conserved throughout Oxa1 homologues. Site‐directed mutagenesis is being conducted to study the importance of this region. Effects caused by the mutations were observed by growing cells harboring oxa1 mutations on glycerol. Molecular approaches have been used to study the affects these mutations have on the ability of Oxa1 to properly insert and assemble its substrates. Our current data suggest the first transmembrane region to be critical for proper and adequate function of the Oxa1 complex. Additional characterization of oxa1 mutants harboring point mutations within this highly conserved region will enable us to further understand the importance of the first transmembrane region and its relevance in the insertion and assembly of Oxa1 substrates. This work is supported by NSF Grant MCB 0347025