A Delicate Interplay of Structure, Dynamics, and Thermodynamics for Function: A High Pressure NMR Study of Outer Surface Protein A
22 February 2012
Publication year: 2012
Source:Biophysical Journal, Volume 102, Issue 4
Outer surface protein A (OspA) is a crucial protein in the infection of Borrelia burgdorferi causing Lyme disease. We studied conformational fluctuations of OspA with high-pressure 15N/1H two-dimensional NMR along with high-pressure fluorescence spectroscopy. We found evidence within folded, native OspA for rapid local fluctuations of the polypeptide backbone in the nonglobular single layer ?-sheet connecting the N- and C-terminal domains with ? > ms) with a minor conformer I, which is almost fully disordered and hydrated for the entire C-terminal part of the polypeptide chain from ?8 to the C-terminus. Conformer I is characterized with ?G 0*= 32 ± 9*kJ/mol and ?V 0*= -140 ± 40*mL/mol, populating only ~0.001% at 40°C at 0.1 MPa, pH 5.9. Because in the folded conformer the receptor binding epitope of OspA is buried in the C-terminal domain, its transition into conformer I under in*vivo conditions may be critical for the infection of B.*burgdorferi. The formation and stability of the peculiar conformer I are apparently supported by a large packing defect or cavity located in the C-terminal domain.
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