A delicate interplay of structure, dynamics, and thermodynamics for function: a high pressure NMR study of outer surface protein A

Biophys J. 2012 Feb 22;102(4):916-26. doi: 10.1016/j.bpj.2011.12.010. Epub 2012 Feb 21.


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 (15)N/(1)H 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 β-sheet connecting the N- and C-terminal domains with τ << ms, which may give the two domains certain independence in mobility and thermodynamic stability. Furthermore, we found that folded, native OspA is in equilibrium (τ >> ms) with a minor conformer I, which is almost fully disordered and hydrated for the entire C-terminal part of the polypeptide chain from β8 to the C-terminus. Conformer I is characterized with ΔG(0) = 32 ± 9 kJ/mol and ΔV(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.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Antigens, Surface / chemistry*
  • Antigens, Surface / metabolism*
  • Bacterial Outer Membrane Proteins / chemistry*
  • Bacterial Outer Membrane Proteins / metabolism*
  • Bacterial Vaccines / chemistry*
  • Bacterial Vaccines / metabolism*
  • Lipoproteins / chemistry*
  • Lipoproteins / metabolism*
  • Models, Molecular
  • Nuclear Magnetic Resonance, Biomolecular*
  • Pressure*
  • Protein Folding
  • Protein Structure, Secondary
  • Spectrometry, Fluorescence
  • Thermodynamics


  • Antigens, Surface
  • Bacterial Outer Membrane Proteins
  • Bacterial Vaccines
  • Lipoproteins
  • OspA protein