FIGURE 7.

Effect of substituting a protonatable residue at the ASR Ser⁸⁶ position (homologous to the Schiff base proton donor in BR, Asp⁹⁶). (A) Inversion of the late phases of proton movement in the full-length (solid line) and truncated (dashed line) double mutant D75E/S86D. Charge movements in single D75E mutants are given for comparison (dashed-dotted and dotted lines for full-length and truncated, respectively). (B) Comparison of the effect of truncation in the wild-type ASR (dashed line) with the effect of S86D mutation in the full-length ASR (solid line).