Modes are generated only at the αδ agonist site. (A) With only a functional αδ site there, are four P_O^ACh and two P_O^TMA populations, as in the WT. (B) Modes are absent in AChRs with only a functional αε or αγ site. (C) Substituting side chains from the γ subunit into the δ subunit (three in loop E and one in the β5–β5′ linker; see Fig. 1) reduces modal activity. Open is down for ACh (−100 mV; 100 µM for αδ and αε, and 30 µM for αγ) and up for TMA (70 mV; 5 mM).