Structure and assembly of the S-layer in C. difficile

Paola Lanzoni-Mangutchi,Robert P Fagan,Filipa Vaz,Jason Wilson,Oishik Banerji,Neil F Fairweather,Kamel El Omari,Joseph A Kirk,Arnaud Baslé,Armin Wagner,Gillian R Douce,Shauna O’Beirne,Paula S Salgado,Per A Bullough,Anna Barwinska-Sendra

doi:10.1038/s41467-022-28196-w

Abstract

Many bacteria and archaea possess a two-dimensional protein array, or S-layer, that covers the cell surface and plays crucial roles in cell physiology. Here, we report the crystal structure of SlpA, the main S-layer protein of the bacterial pathogen Clostridioides difficile, and use electron microscopy to study S-layer organisation and assembly. The SlpA crystal lattice mimics S-layer assembly in the cell, through tiling of triangular prisms above the cell wall, interlocked by distinct ridges facing the environment. Strikingly, the array is very compact, with pores of only ~10 Å in diameter, compared to other S-layers (30–100 Å). The surface-exposed flexible ridges are partially dispensable for overall structure and assembly, although a mutant lacking this region becomes susceptible to lysozyme, an important molecule in host defence. Thus, our work gives insights into S-layer organisation and provides a basis for development of C. difficile-specific therapeutics.

Highlights

Many bacteria and archaea possess a two-dimensional protein array, or S-layer, that covers the cell surface and plays crucial roles in cell physiology
All the S-layer proteins studied in detail have a two-domain organisation, where the assembly domain is responsible for the formation of the paracrystalline layer, and the anchoring domain allows attachment of the S-layer to the cell wall[1]
In C. difficile, the S-layer largely consists of a major S-layer protein, SlpA (Fig. 1a), which assembles into a paracrystalline array enveloping the cell

Summary

Introduction

Many bacteria and archaea possess a two-dimensional protein array, or S-layer, that covers the cell surface and plays crucial roles in cell physiology. We report the crystal structure of SlpA, the main S-layer protein of the bacterial pathogen Clostridioides difficile, and use electron microscopy to study S-layer organisation and assembly. C. difficile infection (CDI) causes substantial morbidity and mortality with severe disease characterised by intestinal inflammation, resulting in extensive damage to the colon[7]. This pathology has largely been attributed to the action of potent toxins that disrupt the cytoskeletal structure and the tight junctions of target cells causing rounding and death[8]. In C. difficile, the S-layer largely consists of a major S-layer protein, SlpA (Fig. 1a), which assembles into a paracrystalline array enveloping the cell. The uniqueness of S-layers across different bacteria makes these arrays attractive targets for speciesspecific therapeutic interventions, provided sufficient structural and functional data are available

Methods

Results

Conclusion