Functional identification of conserved residues involved in Lactobacillus rhamnosus strain GG sortase specificity and pilus biogenesis

Francois P. Douillard*, Pia Rasinkangas, Ingemar von Ossowski, Justus Reunanen, Airi Palva, Willem M. de Vos

*Corresponding author for this work

Research output: Contribution to journalArticleScientificpeer-review

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
Number of pages12
JournalJournal of biological chemistry
Volume289
Issue number22
DOIs
Publication statusPublished - 30 May 2014
MoE publication typeA1 Journal article-refereed

Keywords

  • Bacterial Adhesion
  • Electron Microscopy (EM)
  • Protein Motif
  • Signaling
  • Site-directed Mutagenesis
  • 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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