Plasma membrane Mg2+-ATPase of Pachysolen tannophilus: Characterization and role in alcohol tolerance

Abstract

Following cell fractionation in sucrose density gradients, plasma membrane Mg2+-ATPase from Pachysolen tannophilus was studied. The ATPase displayed an apparent K(m) for ATP of 1.42 mM and was inhibited by high concentrations of Mg2+. The inhibitory effects of ethanol, 1-propanol, 1-butanol, and benzyl alcohol on Mg2+-ATPase were evaluated, and the concentration of each alcohol that inhibited ATPase activity by 50% (IC50) was determined. The IC50 decreased as the chain length of the alcohol increased. Moreover, the IC50 for ATPase activity was similar to the IC50 for growth rate, suggesting an association between impaired growth and ATPase inhibition. Almost complete inhibition of ATPase activity occurred at temperatures approaching 60°C, and the optimal temperature was around 44°C for ATPase from both control and ethanol-treated cells. Inclusion of 50 mM MgCl2 or CaCl2 in the medium did not rescue cells from the deleterious effects of ethanol.