title: Borrelia burgdorferi protein BBK32 binds to soluble fibronectin via the N-terminal 70-kDa region, causing fibronectin to undergo conformational extension.
abstract: BBK32 is a fibronectin (FN)-binding protein expressed on the cell surface of Borrelia burgdorferi, the causative agent of Lyme disease. There is conflicting information about where and how BBK32 interacts with FN. We have characterized interactions of a recombinant 86-mer polypeptide, "Bbk32," comprising the unstructured FN-binding region of BBK32. Competitive enzyme-linked assays utilizing various FN fragments and epitope-mapped anti-FN monoclonal antibodies showed that Bbk32 binding involves both the fibrin-binding and the gelatin-binding domains of the 70-kDa N-terminal region (FN70K). Crystallographic and NMR analyses of smaller Bbk32 peptides complexed, respectively, with (2-3)FNI and (8-9)FNI, demonstrated that binding occurs by β-strand addition. Isothermal titration calorimetry indicated that Bbk32 binds to isolated FN70K more tightly than to intact FN. In a competitive enzyme-linked binding assay, complex formation with Bbk32 enhanced binding of FN with mAbIII-10 to the (10)FNIII module. Thus, Bbk32 binds to multiple FN type 1 modules of the FN70K region by a tandem β-zipper mechanism, and in doing so increases accessibility of FNIII modules that interact with other ligands. The similarity in the FN-binding mechanism of BBK32 and previously studied streptococcal proteins suggests that the binding and associated conformational change of FN play a role in infection.
authors: From the Department of Biology, University of York, York YO10 5DD, United Kingdom and.
authors: Gemma
authors: G
authors: Harris
authors: the Departments of Biomolecular Chemistry and Medicine, University of Wisconsin, Madison, Wisconsin 53706.
authors: Wenjiang
authors: W
authors: Ma
authors: the Departments of Biomolecular Chemistry and Medicine, University of Wisconsin, Madison, Wisconsin 53706.
authors: Lisa M
authors: LM
authors: Maurer
authors: From the Department of Biology, University of York, York YO10 5DD, United Kingdom and jennifer.potts@york.ac.uk.
authors: Jennifer R
authors: JR
authors: Potts
authors: the Departments of Biomolecular Chemistry and Medicine, University of Wisconsin, Madison, Wisconsin 53706 dfmosher@wisc.edu.
authors: Deane F
authors: DF
authors: Mosher
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D025065:Borrelia burgdorferi / Q000235:genetics / Q000378:metabolism* / Q000472:pathogenicity; D018360:Crystallography, X-Ray; D000939:Epitopes / Q000737:chemistry / Q000378:metabolism; D005353:Fibronectins / Q000737:chemistry* / Q000276:immunology / Q000378:metabolism*; D006801:Humans; D008958:Models, Molecular; D008969:Molecular Sequence Data; D019906:Nuclear Magnetic Resonance, Biomolecular; D010446:Peptide Fragments / Q000737:chemistry / Q000378:metabolism; D011485:Protein Binding; D011487:Protein Conformation; D054730:Protein Interaction Domains and Motifs
chemical_list: D001426:Bacterial Proteins; D000939:Epitopes; C067625:FN1 protein, human; D005353:Fibronectins; D010446:Peptide Fragments; C106209:p35 antigen, Borrelia
keywords: Bacterial Adhesion; Beta-Zipper Formation; Borrelia burgdorferi; Fibronectin; Host-Pathogen interactions, FNI Modules; Protein Conformation; Protein Crystallization; Protein Structure