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Journal of Bacteriology, February 2008, p. 1256-1266, Vol. 190, No. 4
0021-9193/08/$08.00+0     doi:10.1128/JB.01078-07
Copyright © 2008, American Society for Microbiology. All Rights Reserved.

Interaction between Two Putative Glycosyltransferases Is Required for Glycosylation of a Serine-Rich Streptococcal Adhesin

Su Bu,¹ Yirong Li,^1, Meixian Zhou,¹ Parastoo Azadin,³ Meiqin Zeng,¹ Paula Fives-Taylor,⁴ and Hui Wu^1,2*

Departments of Pediatric Dentistry,¹ Microbiology, Schools of Dentistry and Medicine, University of Alabama at Birmingham, Birmingham, Alabama 35294,² Complex Carbohydrate Research Center, University of Georgia at Athens, Athens, Georgia 30602,³ Department of Microbiology & Molecular Genetics, University of Vermont, Burlington, Vermont 05405⁴

Received 8 July 2007/ Accepted 3 December 2007

Fap1, a serine-rich glycoprotein, is essential for fimbrial biogenesis and biofilm formation of Streptococcus parasanguinis (formerly S. parasanguis). Fap1-like proteins are conserved in many streptococci and staphylococci and have been implicated in bacterial virulence. Fap1 contains two serine-rich repeat regions that are modified by O-linked glycosylation. A seven-gene cluster has been identified, and this cluster is implicated in Fap1 biogenesis. In this study, we investigated the initial step of Fap1 glycosylation by using a recombinant Fap1 as a model. This recombinant molecule has the same monosaccharide composition profile as the native Fap1 protein. Glycosyl linkage analyses indicated that N-acetylglucosamine (GlcNAc) is among the first group of sugar residues transferred to the Fap1 peptide. Two putative glycosyltransferases, Gtf1 and Gtf2, were essential for the glycosylation of Fap1 with GlcNAc-containing oligosaccharide(s) in both S. parasanguinis as well as in the Fap1 glycosylation system in Escherichia coli. Yeast two-hybrid analysis as well as in vitro and in vivo glutathione S-transferase pull-down assays demonstrated the two putative glycosyltransferases interacted with each other. The interaction domain was mapped to an N-terminal region of Gtf1 that was required for the Fap1 glycosylation. The data in this study suggested that the formation of the Gtf1 and Gtf2 complex was required for the initiation of the Fap1 glycosylation and that the N-terminal region of Gtf1 was necessary.

Published ahead of print on 14 December 2007.

Present address: Department of Laboratory Medicine, Union Hospital, Institution of Immunology, Tongji Medical College, HuaZhong University of Science and Technology, Wuhan, Hubei, People's Republic of China.

This article has been cited by other articles:

• Zhou, M., Peng, Z., Fives-Taylor, P., Wu, H. (2008). A Conserved C-Terminal 13-Amino-Acid Motif of Gap1 Is Required for Gap1 Function and Necessary for the Biogenesis of a Serine-Rich Glycoprotein of Streptococcus parasanguinis. Infect. Immun. 76: 5624-5631 [Abstract] [Full Text]