Figure 5
An acetate molecule fulfills the role of D206 in the structure of D206A HtxB in complex with hypophosphite. (A) Acetate (cyan) forms a salt bridge with R178 and hydrogen bonds to W68 in the D206A complex with hypophosphite (green). Omit maps (black mesh, contoured at 1.2 σ) are shown around the hypophosphite and the acetate molecules. Hydrogen bonds are shown as orange dashes and a single water molecule (HOH) is shown as a red sphere. A superposition of D206A HtxB (green) and WT HtxB (orange), both in complex with hypophosphite, shows that the fold and the degree of domain closure is identical. (B) The acetate (cyan) sits in the plane of the guanidinium group of R178, unlike D206 from the WT structure (beige), which lies 1 Å below the plane at and angle of 75° (shown as black dashed lines). (C) A superposition of WT HtxB (beige) and D206A HtxB (green) in complex with hypophosphite with the ligands shown as spheres. (D) The change in rotamer conformation of M18 between the WT and D206A structures.
