Open AccessStructure of Streptococcus agalactiae tip pilin GBS104: a model for GBS pili assembly and host interactions
Author(s) -
Krishnan Vengadesan,
Dwivedi Prabhat,
Kim Brandon J.,
Samal Alexandra,
Macon Kevin,
Ma Xin,
Mishra Arunima,
Doran Kelly S.,
TonThat Hung,
Narayana Sthanam V. L.
Publication year - 2013
Publication title -
acta crystallographica section d
Language(s) - English
Resource type - Journals
ISSN - 1399-0047
DOI - 10.1107/s0907444913004642
Subject(s) - pilin , fibronectin , homology modeling , pilus , chemistry , binding domain , binding site , streptococcus agalactiae , crystallography , stereochemistry , biology , extracellular matrix , biochemistry , streptococcus , genetics , virulence , bacteria , gene , enzyme
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.