Fig. 5

Binding histogram overlays showing pH responsiveness for respective F48H, T49H, and F48H/T49H CA mutants. X-axis denotes phycoerythrin fluorescence corresponding to EGFR binding. Y-axis denotes number of yeast cells in sample analyzed with given level of EGFR binding. Wild type (red-pH 7.4, pink-pH 5.5) incubated with 1.5 nM EGFR in all figure panels. F48H (dark green-pH 7.4, bright green-pH 5.5) incubated with 4 nM EGFR, T49H (blue-pH 7.4, cyan-pH 5.5) incubated with 1.5 nM EGFR, and F48H/T49H (purple-pH 7.4, lavendar-pH 5.5) incubated with 12 nM EGFR. Unlabeled, negative control yeast population histograms appear in orange in all figure panels. As shown in Additional file 1: Figure S3, F48H and F48H/T49H were displayed at lower levels than T49H and wild type CA