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Acta Crystallogr D Biol Crystallogr. 2013 Jun;69(Pt 6):1073-89. doi: 10.1107/S0907444913004642. Epub 2013 May 15.

Structure of Streptococcus agalactiae tip pilin GBS104: a model for GBS pili assembly and host interactions.

Author information

1
UNESCO Regional Centre for Biotechnology (RCB), Gurgaon 122 016, Haryana, India.

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.

KEYWORDS:

GBS104; group B streptococcus; pili assembly; tip pilins

PMID:
23695252
PMCID:
PMC3663123
DOI:
10.1107/S0907444913004642
[Indexed for MEDLINE]
Free PMC Article

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