Crystal structure of Lyme disease antigen outer surface protein C from Borrelia burgdorferi

The outer surface protein C (OspC) is one of the major host-induced antigen s of Borrelia burgdorferi, the causative agent of Lyme disease. We have sol ved the crystal structure of recombinant OspC to a resolution of 2.5 Angstr om OspC, a largely alpha -helical protein, is a dimer with a characteristic central four-helical bundle formed by association of the two longest helic es from each subunit, OspC is very different from OspA and similar to the e xtracellular domain of the bacterial aspartate receptor and the variant sur face glycoprotein from Trypanosoma brucei, Most of the surface-exposed resi dues of OspC are highly variable among different OspC isolates. The membran e proximal halves of the two long alpha -helices are the only conserved reg ions that are solvent accessible. As vaccination with recombinant OspC has been shown to elicit a protective immune response in mice, these regions ar e candidates for peptide-based vaccines.