Mitochondrial adenosine triphosphatase of the fission yeast, Schizosaccharomyces pombe 972h-. Changes in activity and inhibitor-sensitivity in response to catabolite repression

Publisher Website
Google Scholar
Abstract
The specific activity of mitochondrial ATPase in extracts of S. pombe decreased 2.5-fold as the glucose concentration in the growth medium decreased from 50 mM-15 mM. During the late exponential phase of growth, ATPase activity doubled. Sensitivity to oligomycin and Dio-9 as measured by values for I50 (.mu.g of inhibitor/mg of protein giving 50% inhibition) at pH 6.8 increased 6-fold and 9-fold, respectively, during the initial decrease in ATPase activity, and this degree of sensitivity was maintained for the remainder of the growth cycle. Increased sensitivity to NN''-dicyclohexylcarbodi-imide, triethyltin and venturicidin was observed during the early stage of glucose de-repression. Smaller increases in sensitivity to efrapeptin, aurovertin, 7-chloro-4-nitrobenzo-2-oxa-1,3-diazole, quercetin and spegazzinine occurred. The ATPase of glycerol-grown cells was less sensitive to inhibitors than that of glucose-repressed cells; change in values for I50 were not so marked during the growth cycle of cells growing with glycerol. When submitochondrial particles from glycerol-grown cells were treated by passage through Sephadex G-50, a 4-fold increase in activity was accompanied by increased inhibitor resistance. Gel filtration of submitochondrial particles from glucose-de-repressed cells gave similar results, while loss of ATPase occurred in submitochondrial particles glucose-repressed cells. It is proposed that alterations in sensitivity to inhibitors at different stages of glucose derepression may be partly controlled by a naturally occurring inhibitor of ATPase. The inhibitors tested may be classified into 2 groups on the basis of alterations of sensitivity of the ATPase during physiological modification: oligomycin, Dio-9, NN''-dicyclohexylcarbodi-imide, venturicidin and triethyltin, and efrapeptin, aurovertin, 7-chloro-4-nitrobenzo-2-oxa-1,3-diazole, quercetin and spegazzinine.