Fig. 4.

Mutant cycle analysis indicates that βE153 and βK196 are energetically coupled. (A and C) GABA and PB dose-response curves for singly and doubly substituted alanines at βE153 and βK196. In each case, the double alanine mutant was as adversely affected as the most severely affected single alanine mutant indicating an interaction between βE153 and βK196. Interaction energy (ΔΔG) in A and C is mean ± SEM. (B) Mutant cycle and equations for calculating change in free energy (ΔG) and the overall interaction energy (ΔΔG) are indicated.