FIG 5.

The stability and function of PsaF histidine-to-alanine substitution mutants is restored by low pH. (A) The same strains shown in Fig. 4B were grown at 37°C in BHI buffered to pH 6.5, 6.0, and 5.5, and whole-cell lysates were used to analyze PsaE and PsaF via Western blot. (B) The psaA-gfp plasmid was introduced into these same strains, grown as in panel A, and expression of psaA was determined. ***, P < 0.0001; **, P < 0.001; *, P < 0.01; one-way ANOVA and Dunnett’s multiple-comparison test to compare mean values of each sample to those of the WT at pH 6.5.