FIG. 4.

Crystal structure of the SpeB zymogen showing His340 to be located at the enzyme active site. The figure is based on the crystallographic structure recently presented by Kagawa et al. (9), solved at 1.6 Å resolution. (Left panel) Enlargement of active site showing Cys-192 and His-340 amino acid residues. (Right panel) Overview of SpeB zymogen crystal structure, with blue denoting the 28-kDa mature form, gold denoting the propeptide region, and red denoting the surface-exposed loop containing an Arg-Gly-Asp motif that binds human integrins (9, 28).