NMR-STUDIES OF BORRELIA-BURGDORFERI OSPA, A 28 KDA PROTEIN CONTAININGA SINGLE-LAYER BETA-SHEET

The crystal structure of outer surface protein A (OspA) from Borrelia burgdorferi contains a single-layer beta-sheet connecting the N- and C -terminal globular domains. The central beta-sheet consists largely of polar amino acids and it is solvent-exposed on both faces, which so f ar appears to be unique among known protein structures. We have accomp lished nearly complete backbone H, C and N and C-beta/H-beta assignmen ts of OspA (28 kDa) using standard triple resonance techniques without perdeuteration. This was made possible by recording spectra at a high temperature (45 degrees C). The chemical shift index and N-15 T-1/T-2 ratios show that both the secondary structure and the global conforma tion of OspA in solution are similar to the crystal structure, suggest ing that the unique central beta-sheet is fairly rigid.