Crystal structure of outer surface protein C (OspC) from the Lyme disease spirochete, Borrelia burgdorferi

Outer surface protein C (OspC) is a major antigen on the surface of the Lym e disease spirochete, Borrelia burgdorferi, when it is being transmitted to humans. Crystal structures of OspC have been determined for strains HB19 a nd B31 to 1.8 and 2.5 Angstrom resolution, respectively. The three-dimensio nal structure is predominantly helical. This is in contrast to the structur e of OspA, a major surface protein mainly present when spirochetes are resi ding in the midgut of unfed ticks, which is mostly P-sheet. The surface of OspC that would project away from the spirochete's membrane has a region of strong negative electrostatic potential which may be involved in binding t o positively charged host ligands. This feature is present only on OspCs fr om strains known to cause invasive human disease.