Figure 5.

SulA X-ray structure.A, the SulA monomer has a 3-domain architecture resembling an open fist with an extended thumb. The amino terminal “thumb” domain is yellow, internal core “fingers” domain is green, and carboxy terminal “hand base” is cyan. The catalytic Lys251 (green stick) is covalently bound to PLP (magenta ball-and-stick) in the active site palm (red circle). B, the hydrogen bonds (black dashes), a π-π stacking interaction (thick yellow dash), and covalent bond with residue Lys251 anchor PLP in the active site. Lys281′ is from the opposite protomer. C, the partial positive charges that arise from the orientation of α4 and α5 helix dipole “fingers” that anchor PLP in the active site are shown in rainbow from carboxy terminus negative (red) to amino terminus positive (blue). PLP, pyridoxal phosphate; SulA, cysteate acyl-ACP transferase.