FIG. 4.

Comparison of a filled and an empty type 2 metal binding site. (A and C) Close-ups of the type 2 metal binding sites (shown is the 2F_o-F_c simulated annealing omit electron density map contoured at the 1σ level) with and without zinc (purple sphere), respectively. (B) Superposition of the empty (in dimer_b) and filled (in dimer_a) zinc sites shows how the backbone and side chain atoms of the histidine and aspartate pairs differ. His-114 is the last residue that can be seen in dimer_b. The filled site is shown as a ball-and-stick diagram, and the empty site as bonds.