In vivo activation of plasma membrane H(+)-ATPase hydrolytic activity by complex lipid-bound unsaturated fatty acids in Ustilago maydis.

As an adaptation process to the growth retardation provoked by the presence of nonlethal concentrations of ergosterol biosynthesis inhibitors, Ustilago maydis alters the ratio of linoleic to oleic acid bound to plasma membrane complex lipids [Hernández, A., Cooke, D.T., Lewis, M. & Clarkson, D.T. (1997) Microbiology 143, 3165-3174]. This alteration increases plasma membrane H(+)-ATPase hydrolytic activity. Activation of H(+)-ATPase by the linoleic/oleic acid proportion is noncompetitive, nonessential and only involves changes in the maximum velocity of the pump. Optimum pH, affinity to MgATP and constants for the inhibition by vanadate and erythrosin B remain unchanged. This all indicates that activation of plasma membrane H(+)-ATPase by unsaturated fatty acids differs clearly from glucose-induced activation observed in yeast. Also, it is a physiologically relevant event similar to other, as yet uncharacterized, changes in plasma membrane H(+)-ATPase hydrolytic activity observed in plants and fungi, as part of an adaptation process to different stress conditions.