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Abstract
The fungal and plant plasma membrane H^sup +^-ATPases play critical roles in the physiology of yeast, plant and protozoa cells. We identified two genes encoding two plasma membrane H^sup +^-ATPases in the basidiomycete Ustilago maydis, one protein with higher identity to fungal (um02581) and the other to plant (um01205) H^sup +^-ATPases. Proton pumping activity was 5-fold higher when cells were grown in minimal medium with ethanol compared to cells cultured in rich YPD medium, but total vanadate-sensitive ATPase activity was the same in both conditions. In contrast, the activity in cells cultured in minimal medium with glucose was 2-fold higher than in YPD or ethanol, implicating mechanisms for the regulation of the plasma membrane ATPase activity in U. maydis. Analysis of gene expression of the H^sup +^-ATPases from cells grown under different conditions, showed that the transcript expression of um01205 (plant-type) was higher than that of um02581 (fungal-type). The translation of the two proteins was confirmed by mass spectrometry analysis. Unlike baker's yeast and plant H^sup +^-ATPases, where the activity is increased by a short incubation with glucose or sucrose, respectively, U. maydis H^sup +^-ATPase activity did not change in response to these sugars. Sequence analysis of the two U. maydis H^sup +^-ATPases revealed the lack of canonical threonine and serine residues which are targets of protein kinases in Saccharomyces cerevisiae and Arabidopsis thaliana plasma membrane H^sup +^-ATPases, suggesting that phosphorylation of the U. maydis enzymes occurs at different amino acid residues.[PUBLICATION ABSTRACT]