Figure 7.

Surface aromatic residues in s2a (a) and s2b (b). The boxed regions correspond to residues Ala766–Asp770, which are observed in both the s2a and s2b structures and were used to help assemble the full holo ColH structure (c). This structure is assembled from the crystal structures of the peptidase domains of s1, s2a, s2b and s3, as well as the homology-modeled activator domain of s1. Homology modeling was accomplished using SWISS-MODEL (Biasini et al., 2014 ▶). Surface-exposed aromatic residues of the peptidase domain of s1 and s2a-s2b as well as the conserved collagen-interacting aromatic residues of s3 are shown in yellow. Ca²⁺ is shown as orange spheres. This figure was prepared using PyMOL (Schrödinger).