title: A conserved domain of previously unknown function in Gap1 mediates protein-protein interaction and is required for biogenesis of a serine-rich streptococcal adhesin.
abstract: Fap1-like serine-rich proteins are a new family of bacterial adhesins found in a variety of streptococci and staphylococci that have been implicated in bacterial pathogenesis. A gene cluster encoding glycosyltransferases and accessory Sec components is required for Fap1 glycosylation and biogenesis in Streptococcus parasanguinis. Here we report that the glycosylation-associated protein, Gap1, contributes to glycosylation and biogenesis of Fap1 by interacting with another glycosylation-associated protein, Gap3. Gap1 shares structural homology with glycosyltransferases. The gap1 mutant, like the gap3 mutant, produced an aberrantly glycosylated Fap1 precursor and failed to produce mature Fap1, suggesting that Gap1 and Gap3 might function in concert in the Fap1 glycosylation and biogenesis. Indeed, Gap1 interacted with Gap3 in vitro and in vivo. A Gap1 N-terminal motif, within a highly conserved domain of unknown function (DUF1975) identified in many bacterial glycosyltransferases, was required for the Gap1-Gap3 interaction. Deletion of one, four and nine amino acids within the conserved motif gradually inhibited the Gap1-Gap3 interaction and diminished production of mature Fap1 and concurrently increased production of the Fap1 precursor. Consequently, bacterial adhesion to an in vitro tooth model was also reduced. These data demonstrate that the Gap1-Gap3 interaction is required for Fap1 biogenesis and Fap1-dependent bacterial adhesion.
authors.affiliation: Department of Pediatric Dentistry, Schools of Dentistry and Medicine, University of Alabama, Birmingham, AL 35294, USA.
authors.forename: Yirong
authors.initials: Y
authors.lastname: Li
authors.forename: Yabing
authors.initials: Y
authors.lastname: Chen
authors.forename: Xiang
authors.initials: X
authors.lastname: Huang
authors.forename: Meixian
authors.initials: M
authors.lastname: Zhou
authors.forename: Ren
authors.initials: R
authors.lastname: Wu
authors.forename: Shengli
authors.initials: S
authors.lastname: Dong
authors.forename: David G
authors.initials: DG
authors.lastname: Pritchard
authors.forename: Paula
authors.initials: P
authors.lastname: Fives-Taylor
authors.forename: Hui
authors.initials: H
authors.lastname: Wu
mesh_terms: D018829:Adhesins, Bacterial / Q000235:genetics / Q000378:metabolism*; D000595:Amino Acid Sequence; D001422:Bacterial Adhesion; D017124:Conserved Sequence; D036781:Fimbriae Proteins / Q000235:genetics / Q000378:metabolism*; D017353:Gene Deletion; D015964:Gene Expression Regulation, Bacterial; D005798:Genes, Bacterial; D005816:Genetic Complementation Test; D006031:Glycosylation; D005810:Multigene Family; D016254:Mutagenesis, Insertional; D009154:Mutation; D010641:Phenotype; D054730:Protein Interaction Domains and Motifs; D025941:Protein Interaction Mapping; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D016415:Sequence Alignment; D013291:Streptococcus / Q000235:genetics* / Q000378:metabolism; D020798:Two-Hybrid System Techniques
chemical_list: D018829:Adhesins, Bacterial; D011993:Recombinant Fusion Proteins; C403708:fap1 protein, Streptococcus; D036781:Fimbriae Proteins