Fig. 3.

Structural differences between large and small TMBBs. Here is an example of the additional structural features often found in the larger known TMBBs, which are absent in their smaller counterparts. The protein subdomains that are not in contact with the bilayer tend to receive lower β-hairpin scores, thus lowering the overall β-barrel score when calculated by the original scoring method. The surfaces that contact the bilayer are shown in blue; the protein–protein interaction domains are shown in red; the ‘plug’ domain, which occludes the lumen of the pore is shown in green. (A) Structure of Protease VII/OmpT (1i78; Vandeputte-Rutten et al., 2001). (B) Structure of pilin usher protein PapC (2vqi; Remaut et al., 2008).