Figure 4.

Hexameric structures and putative catalytic sites of PH1704. (A) Ribbon diagram of the hexamer with the threefold NCS axis (perpendicular to the plane of paper) and the three twofold axes (in the plane of paper) are shown. Axis 1 coincides with a crystallographic symmetry axis. Axis 2 and 3 are NCS symmetry axes. (B) Surface representation of the hexamer color-coded by electrostatic potential. The diameter of the center opening is ≈24 Å. (C) Ball and stick model of the putative active site. All of the residues surrounding Cys-100 are shown. (D) A stereogram of the proposed catalytical triad and Glu-15 with the corresponding solvent-flattened experimental map. The distances shown are in Å.