title: A delicate interplay of structure, dynamics, and thermodynamics for function: a high pressure NMR study of outer surface protein A.
abstract: 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.
authors.affiliation: College of Pharmaceutical Sciences, Ritsumeikan University, Shiga, Japan.
authors.forename: Ryo
authors.initials: R
authors.lastname: Kitahara
authors.forename: Alana K
authors.initials: AK
authors.lastname: Simorellis
authors.forename: Kazumi
authors.initials: K
authors.lastname: Hata
authors.forename: Akihiro
authors.initials: A
authors.lastname: Maeno
authors.forename: Shigeyuki
authors.initials: S
authors.lastname: Yokoyama
authors.forename: Shohei
authors.initials: S
authors.lastname: Koide
authors.forename: Kazuyuki
authors.initials: K
authors.lastname: Akasaka
mesh_terms: D000954:Antigens, Surface / Q000737:chemistry* / Q000378:metabolism*; D001425:Bacterial Outer Membrane Proteins / Q000737:chemistry* / Q000378:metabolism*; D001428:Bacterial Vaccines / Q000737:chemistry* / Q000378:metabolism*; D008074:Lipoproteins / Q000737:chemistry* / Q000378:metabolism*; D008958:Models, Molecular; D019906:Nuclear Magnetic Resonance, Biomolecular; D011312:Pressure; D017510:Protein Folding; D017433:Protein Structure, Secondary; D013050:Spectrometry, Fluorescence; D013816:Thermodynamics
chemical_list: D000954:Antigens, Surface; D001425:Bacterial Outer Membrane Proteins; D001428:Bacterial Vaccines; D008074:Lipoproteins; C072045:OspA protein