Characterization of surface antigen from Lyme disease spirochete Borrelia burgdorferi.
Borrelia burgdorferi, the Lyme disease spirochete, possesses a surface protein, VlsE (variable major protein-like sequence, expressed), that undergoes antigenic variation. Unlike conserved regions of other proteins involved in antigenic variation, the most conserved invariable region of VlsE is immunodominant in Lyme-disease patients. Physicochemical analyses of pure recombinant VlsE yielded the following results: The protein appeared oligomeric in solution, with a secondary structure dominated by alpha-helices. Thermal denaturation (pH 7) probed by calorimetry involved two transitions: oligomer-to-monomer conversion (around 40 degrees C) followed by protein unfolding (55 +/- 1 degrees C). Chemical denaturation monitored by far-UV circular dichroism (20 degrees C, pH 7) sensed only polypeptide unfolding and took place in a single transition (Delta G(U)(H(2)O) = 23 +/- 2 kJ/mol). VlsE did not adopt a native structure at pH 3; at pH 10 the stability was significantly reduced. Knowledge of biophysical properties of VlsE may aid in understanding the mechanism of VlsE antigenic variation in B. burgdorferi.
Jones
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K
Molecular and Cellular Biology Graduate Program, Tulane University, New Orleans, Louisiana, 70118-5698
Guidry
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J
Wittung-Stafshede
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P
D000595:Amino Acid Sequence; D000942:Antigens, Bacterial; D000954:Antigens, Surface / Q000378:metabolism; D001426:Bacterial Proteins; D025065:Borrelia burgdorferi / Q000737:chemistry*; D002151:Calorimetry; D002942:Circular Dichroism; D004305:Dose-Response Relationship, Drug; D014644:Genetic Variation; D019791:Guanidine / Q000494:pharmacology; D006863:Hydrogen-Ion Concentration; D008074:Lipoproteins / Q000378:metabolism; D008193:Lyme Disease / Q000378:metabolism*; D008969:Molecular Sequence Data; D011489:Protein Denaturation; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D011994:Recombinant Proteins / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D013144:Spirochaetales / Q000378:metabolism*; D013696:Temperature; D013816:Thermodynamics
D000942:Antigens, Bacterial; D000954:Antigens, Surface; D001426:Bacterial Proteins; D008074:Lipoproteins; D011994:Recombinant Proteins; C105546:VlsE protein, Borrelia burgdorferi; D019791:Guanidine