Figure 3.

The structure of the E3-T18.1 complex. (a) The E3 Fab heavy chain (light blue) forms the majority of the binding interface with only one loop of the light chain (dark blue) making contact with the T18.1 N-terminal domain (green). The pilin lysine (residue Lys 146) that would be covalently linked to the sortase motif at the C-terminus of the next pilin is shown. (b) The E3 epitope mapped onto the surface of T18.1. (i) The T18.1 residues that make up the E3 epitope are shown in light blue (E3 heavy chain contacts) and dark blue (E3 light chain contacts). The pilin lysine is shown in red. (ii) A “top down” view of the epitope highlights that E3 binds across the top of the pilin N-domain and almost entirely via the Fab heavy chain. (N = N-terminus of T.18.1, C = C-terminus, K = pilin lysine).