Mutations of cytochrome c oxidase subunits 1 and 3 in Saccharomyces cerevisiae: assembly defect and compensation.
Eukaryotic cytochrome oxidases are composed of up to 13 subunits, of which three, subunits 1, 2 and 3, are mitochondrially encoded. In this study, yeast mutants were used to investigate the role of subunits 1 and 3 domains on the enzyme assembly. Mutation S203L in subunit 3 which abolished the respiratory growth, decreased cytochrome oxidase content, as measured by optical spectroscopy and immunodetection. Secondary mutations in subunits 1 and 3 restored (partly) the enzyme level. Two reversions reintroduced residues with a hydroxyl group at the primary mutation site (S203T) or in a subunit 3 transmembrane helix close to subunit 1 (G104S). These residues may be involved in hydrogen bonding which strengthen subunits 1-3 interaction. Two other reversions (A224V and Q137K) are located in P-side loops in subunit 1, which may be involved in the enzyme assembly. A mutation in residue A224 has been reported in a family presenting with encephalomyopathy. Surprisingly, the introduction of the 'human' mutation A224S and of a more drastic change A224F had no effect on the yeast enzyme. This might be explained by differences in local folding in the two enzymes.
Meunier
Brigitte
B
Wolfson Institute for Biomedical Research, University College London, Gower Street, London WC1E 6BT, UK. b.meunier@ucl.ac.uk
Taanman
Jan-Willem
JW
D000595:Amino Acid Sequence; D000818:Animals; D002417:Cattle; D003576:Electron Transport Complex IV / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D006801:Humans; D008958:Models, Molecular; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D010101:Oxygen Consumption; D011487:Protein Conformation; D012441:Saccharomyces cerevisiae / Q000201:enzymology*
D003576:Electron Transport Complex IV