HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

J. Biol. Chem., Vol. 282, Issue 14, 10526-10536, April 6, 2007

This Article Full Text Full Text (PDF) All Versions of this Article: 282/14/10526    most recent M608279200v1 Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Baron, M. J. Articles by Madoff, L. C. Search for Related Content PubMed PubMed Citation Articles by Baron, M. J. Articles by Madoff, L. C. Social Bookmarking                      What's this?

Identification of a Glycosaminoglycan Binding Region of the Alpha C Protein That Mediates Entry of Group B Streptococci into Host Cells^*

Miriam J. Baron¹, David J. Filman, Gina A. Prophete, James M. Hogle, and Lawrence C. Madoff

From the Channing Laboratory, Department of Medicine, Brigham & Women's Hospital, and the Department of Biological Chemistry & Molecular Pharmacology, Harvard Medical School, Boston, Massachusetts 02115

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 (Arg¹⁷², Arg¹⁸⁵, or Lys¹⁹⁶) 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.

Received for publication, August 30, 2006 , and in revised form, January 19, 2007.

The nucleotide sequence(s) reported in this paper has been submitted to the GenBank^TM/EBI Data Bank with accession number(s) M97256. [GenBank]

The amino acid sequence of this protein can be accessed through NCBI Protein Database under NCBI accession number AAA26848 [GenBank] .

The atomic coordinates and structure factors (code 2O0I) have been deposited in the Protein Data Bank, Research Collaboratory for Structural Bioinformatics, Rutgers University, New Brunswick, NJ (http://www.rcsb.org/).

^* This work was supported by National Institutes of Health Grants AI38424 (to L. C. M.) and AI059495 (to M. J. B.). The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.

¹ To whom correspondence should be addressed: Channing Laboratory, 181 Longwood Ave., Boston, MA 02115. Tel.: 617-525-0752; Fax: 617-731-1541; E-mail: mbaron{at}partners.org.

CiteULike    Complore    Connotea    Del.icio.us    Digg    Reddit    Technorati    What's this?

This article has been cited by other articles:

				G. Gherardi, M. Imperi, L. Baldassarri, M. Pataracchia, G. Alfarone, S. Recchia, G. Orefici, G. Dicuonzo, and R. Creti Molecular Epidemiology and Distribution of Serotypes, Surface Proteins, and Antibiotic Resistance among Group B Streptococci in Italy J. Clin. Microbiol., September 1, 2007; 45(9): 2909 - 2916. [Abstract] [Full Text] [PDF]