Crystal structure of basal pilin SpaE reveals the molecular basis of its incorporation in the lactobacillar SpaFED pilus

Abhin Kumar Megta, Arjun K. Mishra, Airi Palva, Ingemar von Ossowski, Vengadesan Krishnan*

*Corresponding author for this work

Research output: Contribution to journalArticleScientificpeer-review

Abstract

For some Gram-positive genera and species, the long-extended and adhesive sortase-dependent pilus plays an essential role during host colonization, biofilm formation, and immune modulation. Lactobacillus rhounnosus GG is a gut-adapted commensal strain that harbors the operonic genes for the SpaCBA and SpaFED pili, both being comprised of three different protein subunits termed the backbone, tip, and basal pilins. Crystal structures of the backbone pilins (SpaA and SpaD) have recently been solved, and here we describe the high-resolution (1.5 angstrom) structural determination of the SpaE basal pilin. SpaE consists of two immunoglobulin-like CnaB domains, with each displaying a spontaneously formed internal isopeptide bond, though apparently slow forming in the N-terminal domain. Remarkably, SpaE contains an atypically lengthy unstructured C-terminal tail, along with an YPKN pilin motif peptide, which is normally reserved for backbone subunits. Based on our analysis of the crystal structure data, we provide a molecular model for the basal positioning of the SpaE pilin within the SpaFED pilus.

Original languageEnglish
Pages (from-to)74-84
Number of pages11
JournalJournal of Structural Biology
Volume207
Issue number1
DOIs
Publication statusPublished - 1 Jul 2019
MoE publication typeA1 Journal article-refereed

Keywords

  • Adhesion
  • Probiotics
  • Basal pilin
  • Host-microbe interaction
  • Sortase-dependent pili
  • Pilus anchoring
  • GRAM-POSITIVE BACTERIA
  • RAY-DIFFRACTION ANALYSIS
  • RHAMNOSUS GG
  • CORYNEBACTERIUM-DIPHTHERIAE
  • INTRAMOLECULAR ISOPEPTIDE
  • CRYSTALLOGRAPHIC ANALYSIS
  • STABILIZING ISOPEPTIDE
  • PYOGENES PILUS
  • SPACBA PILUS
  • PROTEIN

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