Figure 3.

Functional Expression of PMA4-GFP and PMA4ΔCter-GFP in Saccharomyces cerevisae.

(A) A null mutant strain of S. cerevisae relying on conditional expression of S. cerevisae PM H⁺-ATPase PMA1 was transformed with a plasmid bearing PMA4-GFP. After preculture in galactose medium, transformed and untransformed cells were transferred to glucose medium for 16 h to switch off PMA1 expression, then the microsomal fraction was prepared and an ATPase assay performed in the presence or absence of vanadate, a PM H⁺-ATPase inhibitor. The specific activity of membranes containing only residual PMA1 (0.043 μmol Pi × min⁻¹ × mg⁻¹ protein) was taken as 100%.

(B) Serial 10-fold dilutions of strains expressing the indicated PMA4-derived constructs after 5-fluoroorotic acid selection.