Isolation of Supernumerary yeast ATP synthase subunits e and i. Characterization of subunit i and disruption of its structural gene ATP18

• Published in: The Journal of biological chemistry Vol. 274; no. 1; pp. 543 - 548
• Main Authors: Vaillier, J. (Universite Victor Segalen, Bordeaux, France.), Arselin, G, Graves, P.V, Camougrand, N, Velours, J
• Format: Journal Article
• Language: English
• Published: United States 01-01-1999
• Subjects: ACTIVIDAD ENZIMATICA; ACTIVITE ENZYMATIQUE; Amino Acid Sequence; AMINO ACID SEQUENCES; ATP18 GENE; Base Sequence; CHEMICAL COMPOSITION; COMPOSICION QUIMICA; COMPOSITION CHIMIQUE; DNA, Fungal; ENZYMIC ACTIVITY; FENOTIPOS; FOSFORILACION; GENBANK/AF073791; GENE; GENES; Genes, Fungal; GROWTH RATE; H+-TRANSPORTING; HIDROLASAS; HYDROLASE; HYDROLASES; INDICE DE CRECIMIENTO; MITOCHONDRIA; MITOCHONDRIE; MITOCONDRIA; MOLECULAR SEQUENCE DATA; MOLECULAR WEIGHT; MUTANT; MUTANTES; MUTANTS; Mutation; NUCLEOTIDE SEQUENCE; OXIDATIVE PHOSPHORYLATION; PESO MOLECULAR; PHENOTYPE; PHENOTYPES; PHOSPHORYLATION; POIDS MOLECULAIRE; Proton-Translocating ATPases - genetics; Proton-Translocating ATPases - isolation & purification; Proton-Translocating ATPases - metabolism; PYROPHOSPHATASES; SACCHAROMYCES CEREVISIAE; Saccharomyces cerevisiae - enzymology; Saccharomyces cerevisiae - genetics; SECUENCIA NUCLEOTIDICA; SEQUENCE NUCLEOTIDIQUE; TAUX DE CROISSANCE
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.274.1.543

Two subunits of the yeast ATP synthase have been isolated. Subunit e was found loosely associated to the complex. Triton X-100 at a 1% concentration removed this subunit from the ATP synthase. The N-terminal sequencing of subunit i has been performed. The data are in agreement with the sequence of the predicted product of a DNA fragment of Saccharomyces cerevisiae chromosome XIII. The ATP18 gene encodes subunit i, which is 59 amino acids long and corresponds to a calculated mass of 6687 Da. Its pI is 9.73. It is an amphiphilic protein having a hydrophobic N-terminal part and a hydrophilic C-terminal part. It is not apparently related to any subunit described in other ATP synthases. The null mutant showed low growth on nonfermentable medium. Mutant mitochondria display a low ADP/O ratio and a decrease with time in proton pumping after ATP addition. Subunit i is associated with the complex; it is not a structural component of the enzyme but rather is involved in the oxidative phosphorylations. Similar amounts of ATP synthase were measured for wild-type and null mutant mitochondria. Because 2-fold less specific ATPase activity was measured for the null mutant than for the wild-type mitochondria, we make the hypothesis that the observed decrease in the turnover of the mutant enzyme could be linked to a proton translocation defect through F0.