Fig. 5.

Mutation of the extracellular Ho³⁺ binding site gives a yeast phenotype that displays sensitivity toward low pH. Yeast complementation test was performed essentially as described in Fig. 4. Thus, yeast expressing single point mutants of the extracellular Ho³⁺ site were spotted on either galactose-containing media (Gal) at pH 5.5 or glucose-containing media (Glu) with different pH values (pH 6.5–3.5) in two different concentrations (OD₆₀₀ of 0.1 and 0.01).