title: Structure of Streptococcus agalactiae tip pilin GBS104: a model for GBS pili assembly and host interactions.
abstract: The crystal structure of a 75 kDa central fragment of GBS104, a tip pilin from the 2063V/R strain of Streptococcus agalactiae (group B streptococcus; GBS), is reported. In addition, a homology model of the remaining two domains of GBS104 was built and a model of full-length GBS104 was generated by combining the homology model (the N1 and N4 domains) and the crystal structure of the 75 kDa fragment (the N2 and N3 domains). This rod-shaped GBS104 model is constructed of three IgG-like domains (the N1, N2 and N4 domains) and one vWFA-like domain (the N3 domain). The N1 and N2 domains of GBS104 are assembled with distinct and remote segments contributed by the N- and C-termini. The metal-binding site in the N3 domain of GBS104 is in the closed/low-affinity conformation. Interestingly, this domain hosts two long arms that project away from the metal-binding site. Using site-directed mutagenesis, two cysteine residues that lock the N3 domain of GBS104 into the open/high-affinity conformation were introduced. Both wild-type and disulfide-locked recombinant proteins were tested for binding to extracellular matrix proteins such as collagen, fibronectin, fibrinogen and laminin, and an increase in fibronectin binding affinity was identified for the disulfide-locked N3 domain, suggesting that induced conformational changes may play a possible role in receptor binding.
authors.affiliation: UNESCO Regional Centre for Biotechnology (RCB), Gurgaon 122 016, Haryana, India.
authors.forename: Vengadesan
authors.initials: V
authors.lastname: Krishnan
authors.forename: Prabhat
authors.initials: P
authors.lastname: Dwivedi
authors.forename: Brandon J
authors.initials: BJ
authors.lastname: Kim
authors.forename: Alexandra
authors.initials: A
authors.lastname: Samal
authors.forename: Kevin
authors.initials: K
authors.lastname: Macon
authors.forename: Xin
authors.initials: X
authors.lastname: Ma
authors.forename: Arunima
authors.initials: A
authors.lastname: Mishra
authors.forename: Kelly S
authors.initials: KS
authors.lastname: Doran
authors.forename: Hung
authors.initials: H
authors.lastname: Ton-That
authors.forename: Sthanam V L
authors.initials: SV
authors.lastname: Narayana
mesh_terms: D001665:Binding Sites; D016326:Extracellular Matrix Proteins / Q000502:physiology; D036781:Fimbriae Proteins / Q000737:chemistry* / Q000235:genetics / Q000502:physiology; D008958:Models, Molecular; D016297:Mutagenesis, Site-Directed; D011485:Protein Binding; D011487:Protein Conformation; D013292:Streptococcus agalactiae / Q000737:chemistry* / Q000235:genetics / Q000502:physiology; D014961:X-Ray Diffraction
chemical_list: D016326:Extracellular Matrix Proteins; D036781:Fimbriae Proteins
keywords: GBS104; group B streptococcus; pili assembly; tip pilins