2O0I

crystal structure of the R185A mutant of the N-terminal domain of the Group B Streptococcus Alpha C protein

Summary for 2O0I

• Entry DOI: 10.2210/pdb2o0i/pdb
• Related: 1YWM
• Descriptor: C protein alpha-antigen (1 entity in total)
• Functional Keywords: surface active protein, beta sandwich, fibronectin fold, antiparallel three-helix bundle
• Biological source: Streptococcus agalactiae serogroup Ia
• Cellular location: Secreted, cell wall ; Peptidoglycan-anchor : Q02192
• Total number of polymer chains: 1
• Total formula weight: 19924.24

Authors

Hogle, J.M.,Filman, D.J.,Baron, M.J.,Madoff, L.C.,Iglesias, A. (deposition date: 2006-11-27, release date: 2007-02-06, Last modification date: 2023-08-30)

Primary citation

Baron, M.J.,Filman, D.J.,Prophete, G.A.,Hogle, J.M.,Madoff, L.C.
Identification of a glycosaminoglycan binding region of the alpha C protein that mediates entry of group B streptococci into host cells.
J.Biol.Chem., 282:10526-10536, 2007

PubMed Abstract: Group B Streptococcus (GBS) frequently colonizes the human gastrointestinal and gynecological tracts and less frequently causes deep tissue infections. The transition between colonization and infection depends upon the ability of the organism to cross epithelial barriers. The alpha C protein (ACP) on the surface of GBS contributes to this process. A virulence factor in mouse models of infection, and prototype for a family of Gram-positive bacterial surface proteins, ACP facilitates GBS entry into human cervical epithelial cells and movement across cell layers. ACP binds to host cell surface glycosaminoglycan (GAG). From crystallography, we have identified a cluster of basic residues (BR2) that is a putative GAG binding area in Domain 2, near the junction of the N-terminal domain of ACP and the first of a series of tandem amino acid repeats. D2-R, a protein construct including this region, binds to cells similarly to full-length ACP. We now demonstrate that the predicted charged BR2 residues confer GAG binding; site-directed mutagenesis of these residues (Arg(172), Arg(185), or Lys(196)) eliminates cell-binding activity of construct D2-R. In addition, we have constructed a GBS strain expressing a variant ACP with a charge-neutralizing substitution at residue 185. This strain enters host cells less effectively than does the wild-type strain and similarly to an ACP null mutant strain. The point mutant strain transcytoses similarly to the wild-type strain. These data indicate that GAG-binding activity underlies ACP-mediated cellular entry of GBS. GBS entry into host cells and transcytosis of host cells may occur by distinct mechanisms.

PubMed: 17259175
DOI: 10.1074/jbc.M608279200

Experimental method

X-RAY DIFFRACTION (3.1 Å)