Salmonella Phage S16 Tail Fiber Adhesin Features a Rare Polyglycine Rich Domain for Host Recognition

Structure. 2018 Dec 4;26(12):1573-1582.e4. doi: 10.1016/j.str.2018.07.017. Epub 2018 Sep 20.

Abstract

The ability of phages to infect specific bacteria has led to their exploitation as bio-tools for bacterial remediation and detection. Many phages recognize bacterial hosts via adhesin tips of their long tail fibers (LTFs). Adhesin sequence plasticity modulates receptor specificity, and thus primarily defines a phage's host range. Here we present the crystal structure of an adhesin (gp38) attached to a trimeric β-helical tip (gp37) from the Salmonella phage S16 LTF. Gp38 contains rare polyglycine type II helices folded into a packed lattice, herein designated "PGII sandwich." Sequence variability within the domain is limited to surface-exposed helices and distal loops that form putative receptor-binding sites. In silico analyses revealed a prevalence of the adhesin architecture among T-even phages, excluding the archetypal T4 phage. Overall, S16 LTF provides a valuable model for understanding binding mechanisms of phage adhesins, and for engineering of phage adhesins with expandable or modulated host ranges.

Keywords: Salmonella; X-ray crystallography; bacteriophage; polyglycine sandwich; polyglycine type II helix.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Binding Sites
  • Computer Simulation
  • Crystallography, X-Ray
  • Hydrophobic and Hydrophilic Interactions
  • Models, Molecular
  • Peptides / chemistry
  • Peptides / metabolism*
  • Protein Conformation
  • Protein Domains
  • Salmonella Phages / chemistry
  • Salmonella Phages / metabolism*
  • Viral Tail Proteins / chemistry*
  • Viral Tail Proteins / metabolism*

Substances

  • Peptides
  • Viral Tail Proteins
  • polyglycine