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Journal of Bacteriology, July 2009, p. 4195-4206, Vol. 191, No. 13
0021-9193/09/$08.00+0     doi:10.1128/JB.01673-08
Copyright © 2009, American Society for Microbiology. All Rights Reserved.

Molecular Dissection of the secA2 Locus of Group B Streptococcus Reveals that Glycosylation of the Srr1 LPXTG Protein Is Required for Full Virulence{triangledown} ,{dagger}

Michel-Yves Mistou,1,2* Shaynoor Dramsi,1,2 Sara Brega,1,2 Claire Poyart,1,2,3,4 and Patrick Trieu-Cuot1,2

Institut Pasteur, Unité de Biologie des Bactéries Pathogènes à Gram-Positif,1 URA CNRS 2172, 25 Rue du Dr. Roux, 75724 Paris Cedex 15, France,2 Université Paris Descartes,3 INSERM 4567-UMR CNRS 810, Paris 75014, France4

Received 28 November 2008/ Accepted 14 April 2009

In streptococci, the secA2 locus includes genes encoding the following: (i) the accessory Sec components (SecA2, SecY2, and at least three accessory secretion proteins), (ii) two essential glycosyltranferases (GTs) (GtfA and GtfB), (iii) a variable number of dispensable additional GTs, and (iv) a secreted serine-rich LPXTG protein which is glycosylated in the cytoplasm and transported to the cell surface by this accessory Sec system. The secA2 locus of Streptococcus agalactiae strain NEM316 is structurally related to those found in other streptococci and encodes the serine-rich surface protein Srr1. We demonstrated that expression of Srr1 but not that of the SecA2 components and the associated GTs is regulated by the standalone transcriptional regulator Rga. Srr1 is synthesized as a glycosylated precursor, secreted by the SecA2 system, and anchored to the cell wall by the housekeeping sortase A. Srr1 was localized preferentially at the old poles. GtfA and/or GtfB, but not the six additional GTs, is essential for the production of Srr1. These GTs are involved in the attachment of GlcNac and sialic acid to Srr1. Full glycosylation of Srr1 is associated with the cell surface display of a protein that is more resistant to proteolytic attack. Srr1 contributes to bacterial adherence to human epithelial cell lines and virulence in a neonatal rat model. The extent of Srr1 glycosylation by GtfC to -H modulates bacterial adherence and virulence.

* Corresponding author. Mailing address: Unité de Biologie des Bactéries Pathogènes à Gram-Positif, Institut Pasteur, 25 rue du Dr. Roux, 75724 Paris Cedex, France. Phone: 33 1 44 38 95 92. Fax: 33 1 45 68 89 38. E-mail: mistou{at}pasteur.fr

{triangledown} Published ahead of print on 24 April 2009.

{dagger} Supplemental material for this article may be found at http://jb.asm.org/.

Journal of Bacteriology, July 2009, p. 4195-4206, Vol. 191, No. 13
0021-9193/09/$08.00+0     doi:10.1128/JB.01673-08
Copyright © 2009, American Society for Microbiology. All Rights Reserved.





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