Fig. 1.

Electron density map of the α-NPG ligand site in molecule A, LacY G46W/G262W. Density contoured at 1.3σ (golden yellow mesh) is superimposed on the cartoon representation of the structure. Residues surrounding the ligand are labeled. Carbon atoms in α-NPG are shown in orange, nitrogen in blue, and oxygen in red. Side-chain atoms are shown as carbon in yellow, nitrogen in blue, oxygen in red, and sulfur in light yellow. Broken blue lines show hydrogen bonds with lengths labeled in Å. The cytoplasmic side is upward, and the normal to the membrane plane is approximately vertical.