The access of metabolites into yeast mitochondria in the presence and absence of the voltage dependent anion selective channel (YVDAC1).

Since yeast Saccharomyces cerevisiae mutants depleted of the voltage dependent anion selective channel (YVDAC1) are still able to grow on a non-fermentable carbon source, a functional transport system in the outer mitochondrial membrane must exist to support the access of metabolites into mitochondria. It was assumed that the properties of the system could be inferred from the differences in the results observed between wild type and mutant mitochondria since no crucial differences in this respect between the two types of mitoplasts were observed. YVDAC1-depleted mitochondria displayed a highly reduced permeability of the outer membrane, which was reflected in increased values of K0.

Electron partitioning between the two branching quinol-oxidizing pathways in Acanthamoeba castellanii mitochondria during steady-state state 3 respiration.

Amoeba mitochondria possess a respiratory chain with two quinol-oxidizing pathways: the cytochrome pathway and the cyanide-resistant alternative oxidase pathway. The ADP/O method, based on the non-phosphorylating property of alternative oxidase, was used to determine contributions of both pathways in overall state 3 respiration in the presence of GMP (an activator of the alternative oxidase in amoeba) and succinate as oxidizable substrate. This method involves pair measurements of ADP/O ratios plus and minus benzohydroxamate (an inhibitor of the alternative oxidase).

The respiration of cells and mitochondria of porin deficient yeast mutants is coupled.

Several mutants of yeast lacking the porin gene have been found stable and viable on glucose or glycerol media. Ethanol-supported respiration of porin-free mutant and wild cells appeared equally coupled in vivo being similarly depressed by inhibitors of ADP/ATP translocase or of ATP synthase and stimulated by the uncoupler FCCP. The absence of porin in isolated mutant mitochondria hardly impaired the electron flux but increased the requirement for Mg2+ (or Ca2+) and for ADP and carboxyatractylate concentrations necessary to drive effectively state 3 - state 4 and state 4 - state 3 transitions, respectively.

Inhibition by valinomycin of atractyloside binding to the membrane-bound ADP/ATP carrier: counteracting effect of cations.

The atractyloside binding capacity of rat heart mitochondria, but not the binding affinity, was markedly decreased by preincubation of the mitochondria with valinomycin in isotonic KCl medium. Maximum inhibition was attained with 5 ng of valinomycin per mg of mitochondrial protein; it corresponded to a 40% decrease of the atractyloside binding capacity. The inhibitory effect of valinomycin was maximal between pH 7.