Functional Identification of Conserved Residues Involved in Lactobacillus rhamnosus Strain GG Sortase Specificity and Pilus Biogenesis

F.P. Douillard, P. Rasinkangas, I. von Ossowski, J. Reunanen, A. Palva, W.M. de Vos

Research output: Contribution to journalArticleAcademicpeer-review

13 Citations (Scopus)

Abstract

In Gram-positive bacteria, sortase-dependent pili mediate the adhesion of bacteria to host epithelial cells and play a pivotal role in colonization, host signaling, and biofilm formation. Lactobacillus rhamnosus strain GG, a well known probiotic bacterium, also displays on its cell surface mucus-binding pilus structures, along with other LPXTG surface proteins, which are processed by sortases upon specific recognition of a highly conserved LPXTG motif. Bioinformatic analysis of all predicted LPXTG proteins encoded by the L. rhamnosus GG genome revealed a remarkable conservation of glycine residues juxtaposed to the canonical LPXTG motif. Here, we investigated and defined the role of this so-called triple glycine (TG) motif in determining sortase specificity during the pilus assembly and anchoring. Mutagenesis of the TG motif resulted in a lack or an alteration of the L. rhamnosus GG pilus structures, indicating that the TG motif is critical in pilus assembly and that they govern the pilin-specific and housekeeping sortase specificity. This allowed us to propose a regulatory model of the L. rhamnosus GG pilus biogenesis. Remarkably, the TG motif was identified in multiple pilus gene clusters of other Gram-positive bacteria, suggesting that similar signaling mechanisms occur in other, mainly pathogenic, species.
Original languageEnglish
Pages (from-to)15764-15775
JournalJournal of Biological Chemistry
Volume289
Issue number22
DOIs
Publication statusPublished - 2014

Keywords

  • complete genome sequence
  • gram-positive bacteria
  • enterococcus-faecium isolate
  • group-b streptococcus
  • lactic-acid bacteria
  • lactococcus-lactis
  • corynebacterium-diphtheriae
  • bacillus-anthracis
  • pilin subunit
  • reveals pili

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