Figure 5. Details of the Bd3459 endopeptidase:Bd3460 auto-immunity protein complex.

(a) An extensive interaction places all six ankyrin repeats of Bd3460 (ribbon form, red) over the upper, transpeptidase lobe of Bd3459 (ribbon form, helices sky blue, strands yellow; active site serine in stick form and denoted by asterisk; active site extended loop, dark blue). A small pocket of solvent exists at the protein interface. (b) Orthogonal view from a, demonstrating that AR1:6 of Bd3460 effectively wrap around the final helix of the Bd3459 transpeptidase domain, interacting via the helix-turn-helix section of the repeats. (c) Interacting partners have been rotated like an open book from orientation in a, Bd3459 90° to left, Bd3460 90° to right. The interaction face of Bd3459 (blue) is comprised of two continuous regions that abut, but do not comprise the active site cleft (catalytic serine coloured red). In contrast, the interacting face of Bd3460 (pink) is formed from a single face of the protein.