Figure 7
From: A new family of periplasmic-binding proteins that sense arsenic oxyanions
Overlay of the residues forming the ligand binding-sites. (A) Comparison of a phosphate-bound AioX (yellow carbon atoms) and the phosphonate-bound PhnD (blue carbon atoms). For clarity, all atoms in the phosphonate molecule are coloured blue. All AioX residues involved in phosphate binding are shown and labelled. The two AioX-specific hydrogen bonds to the phosphate ion are denoted by dashed lines (2.5 Å and 2.6 Å from D210 oxygen and C106 sulphur to phosphate oxygen, respectively). Residues numbered with the asterisk refer to the PhnD structure and they are specific for that protein. (B) Comparison of a phosphate-bound AioX (all yellow) and arsenite-bound AioX (purple carbons). Hydrogen bonds with arsenite are denoted by dashed lines while the interactions seen only in the presence of phosphate (same as in 7 A) are shown by dotted lines.
