title: Cellular and functional analysis of four mutations located in the mitochondrial ATPase6 gene.
abstract: The smallest rotary motor of living cells, F0F1-ATP synthase, couples proton flow-generated by the OXPHOS system-from the intermembrane space back to the matrix with the conversion of ADP to ATP. While all mutations affecting the multisubunit complexes of the OXPHOS system probably impact on the cell's output of ATP, only mutations in complex V can be considered to affect this output directly. So far, most of the F0F1-ATP synthase variations have been detected in the mitochondrial ATPase6 gene. In this study, the four most frequent mutations in the ATPase6 gene, namely L156R, L217R, L156P, and L217P, are studied for the first time together, both in primary cells and in cybrid clones. Arginine ("R") mutations were associated with a much more severe phenotype than Proline ("P") mutations, in terms of both biochemical activity and growth capacity. Also, a threshold effect in both "R" mutations appeared at 50% mutation load. Different mechanisms seemed to emerge for the two "R" mutations: the F1 seemed loosely bound to the membrane in the L156R mutant, whereas the L217R mutant induced low activity of complex V, possibly the result of a reduced rate of proton flow through the A6 channel.
authors.affiliation: Unidad de Investigacion Medica en Genetica, Centro Medico Nacional, Instituto Mexicano del Seguro Social, Mexico City, Mexico.
authors.forename: Martha Elisa
authors.initials: ME
authors.lastname: Vazquez-Memije
authors.forename: Teresa
authors.initials: T
authors.lastname: Rizza
authors.forename: Maria Chiara
authors.initials: MC
authors.lastname: Meschini
authors.forename: Claudia
authors.initials: C
authors.lastname: Nesti
authors.forename: Filippo Maria
authors.initials: FM
authors.lastname: Santorelli
authors.forename: Rosalba
authors.initials: R
authors.lastname: Carrozzo
mesh_terms: D001120:Arginine / Q000235:genetics; D002478:Cells, Cultured; D005347:Fibroblasts / Q000473:pathology; D050259:Genes, Mitochondrial; D006801:Humans; D007700:Kinetics; D025261:Mitochondrial Proton-Translocating ATPases / Q000235:genetics* / Q000378:metabolism; D020125:Mutation, Missense; D010085:Oxidative Phosphorylation; D010641:Phenotype; D011392:Proline / Q000235:genetics
chemical_list: C501005:MT-ATP6 protein, human; D001120:Arginine; D011392:Proline; D025261:Mitochondrial Proton-Translocating ATPases