Modifications of oxidative phosphorylations in mitochondria isolated from a mutant of Saccharomyces cerevisiae. Possible alterations of the phosphate transport.
Mutants of Saccharomyces cerevisiae were isolated which supported two unlinked nuclear mutations conferring thermosensitivity and cold sensitivity respectively, and a mitochondrial one conferring paromomycin sensitivity. Mitochondria isolated from such a mutant exhibited modifications of several phosphate-requiring functions: (a) kinetic parameters of the phosphate dependence of ATP synthesis were modified; (b) in the absence of phosphate the inner mitochondrial membrane exhibited a high proton leakage; (c) mutant mitochondria always exhibited a poor respiratory control and required tenfold more phosphate to reach a maximal state 3 of respiration; (d) phosphate transport, as measured by swelling experiments, was mersalyl-insensitive and, consequently, state 3 of the respiration and ATP synthesis remained less mersalyl-sensitive than in wild-type mitochondria. Analysis of the mitochondrial metabolism of diploid and segregant strains indicates that these modifications are related to the cryosensitive phenotype; however, at present, a cooperative effect of the mitochondrial mutation cannot be eliminated. It is proposed that the phosphate carrier itself or a regulatory element was modified.
Manon
S
S
Institut de Biochimie Cellulaire et de Neurochimie du CNRS, Bordeaux, France.
Guerin
M
M
D000255:Adenosine Triphosphate / Q000096:biosynthesis; D001692:Biological Transport; D004352:Drug Resistance, Microbial; D008634:Mersalyl / Q000494:pharmacology; D008928:Mitochondria / Q000378:metabolism*; D009154:Mutation; D010085:Oxidative Phosphorylation; D010101:Oxygen Consumption; D010710:Phosphates / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism*
D010710:Phosphates; D008634:Mersalyl; D000255:Adenosine Triphosphate