FIGURE 5.

The citrate binding distal pocket. A, stereo view with the citrate and residues contacting the citrate or magnesium depicted as cylinders. The 2F_o − F_c map contoured at the 1σ level is shown for the citrate-Mg²⁺. B and C, two views of the citrate-Mg²⁺ bound in the pocket of AcnR with the protein surface displayed to emphasize the shape of the pocket. D, superposition of the heavy atom derivative and native Form I structures. The 2F_o − F_c map at 1σ is shown for the gold ion. The gold in the derivative crystal displaces the citrate-Mg²⁺.