Estimated shift contributions for separate binding sites. (A) Best solutions to the models described in the Discussion of the main text. Wu50 data are based on eight mutants. Wu50 (reduced) data are based on a reduced set of five mutations (residual effect fixed to black bar). Wu161 data are based on five mutants. For O (365–416) R362Q/W454A, only the black bar exists. (B) Correlation between experimental data and model data as described in the Discussion of the main text. Color coding as in A.