K62W structure at the second PL⁻ site. (A and B) The Apo-K62W structural model was generated by molecular replacement with 3SPI residue 62 as Trp (A), and final electron density and a model with a decylmaltoside detergent head group are shown (B). In each case, 2fo-fc electron density at 2.0-Å resolution, contoured at 1σ, is shown in gray. Positive fo-fc electron density at 2.0-Å resolution, contoured at 3σ, is shown in green. Pink indicates carbon atoms of the residue mutated; orange indicates carbon atoms of the wild-type residues; cyan indicates carbon atoms of the ligand (DM); blue indicates nitrogen atoms; red indicates oxygen atoms.