FIGURE 4.

Position of Ag⁺-sensitive residues in a two-dimensional topological map of subunit a. The suggested regions of α-helical secondary structure depicted in the 1–2 and 3–4 loops are based upon NMR chemical shift analysis of subunit a in chloroform-methanol-H₂O (4:4:1) solvent (53). Residues that are most sensitive to inhibition by Ag⁺ are shown in red (>85% inhibition), orange (66–85% inhibition), and brown (46–65% inhibition). The relative depth of placement of the five TMHs of subunit a in the lipid bilayer is based upon cross-linking experiments as described elsewhere (19).