The proton-translocating ATPase of Candida tropicalis plasma membrane

Mercaptoethanol and dithiothreitol decrease the difference of electrochemical proton potentials across the yeast plasma and vacuolar membranes and activate their H(+)-ATPases

Mercaptoethanol and dithiothreitol (DTT) inhibited the acidification of external medium by Saccharomyces carlsbergensis cells and protoplasts during glucose oxidation. The inhibition was also observed when cells were incubated with mercaptoethanol or when mercaptoethanol and DTT were used to prepare protoplasts. Experiments with S. carlsbergensis plasma membrane vesicles and vacuoles showed these thiol reagents to inhibit ATP-dependent generation of delta pH and Em across plasma membrane vesicles and vacuoles but to activate their H(+)-ATPases. Mercaptoethanol and DTT are suggested to de-energize plasmalemma as well as tonoplast by increasing their H(+)-permeability and to disturb the cell ion homeostasis.

Dimorphism-associated changes in plasma membrane H(+)-ATPase activity of Candida albicans

In situ plasma membrane H(+)-ATPase activity was monitored during pH-regulated dimorphism of Candida albicans using permeabilized cells. ATPase activity was found to increase in both the bud and germ tube forming populations at 135 min which coincides with the time of evagination. Upon reaching the terminal phenotype the mycelial form exhibited higher H(+)-ATPase activity as compared to the yeast form. At the time of evagination H(+)-efflux exhibited an increase. K+ depletion resulted in attenuated ATPase activity and glucose induced H(+)-efflux. The results demonstrate that ATPase may play a regulatory role in dimorphism of C. albicans and K+ acts as a modulator.