Figure 4.
Energetic coupling of αPhe 135 with αLeu 210 and αLeu 273, and coupling among residues at equivalent positions of the ε- and δ-subunits. In each two-dimensional mutant cycle, the four lines indicate changes in channel gating free energy by the indicated mutations, relative to that for the wild-type AChR; the free energy difference between any pair of parallel lines gives the first-order coupling free energy (ΔΔGint) for the residue pair. For each mutant AChR, single-channel currents elicited by 300 μm ACh are shown at a bandwidth of 10 kHz.