The extracellular juncture domains in the intimin passenger adopt a constitutively extended conformation inducing restraints to its sphere of action

Julia Weikum,Line Vejby Jægerum,Katsutoshi Hori,J Preben Morth,Shogo Yoshimoto,Alina Kulakova,Pernille Harris,Jack C Leo,Marie Skepö,Monika Schütz,Giulio Tesei

doi:10.1038/s41598-020-77706-7

Abstract

Enterohemorrhagic and enteropathogenic Escherichia coli are among the most important food-borne pathogens, posing a global health threat. The virulence factor intimin is essential for the attachment of pathogenic E. coli to the intestinal host cell. Intimin consists of four extracellular bacterial immunoglobulin-like (Big) domains, D00–D2, extending into the fifth lectin subdomain (D3) that binds to the Tir-receptor on the host cell. Here, we present the crystal structures of the elusive D00–D0 domains at 1.5 Å and D0–D1 at 1.8 Å resolution, which confirms that the passenger of intimin has five distinct domains. We describe that D00–D0 exhibits a higher degree of rigidity and D00 likely functions as a juncture domain at the outer membrane-extracellular medium interface. We conclude that D00 is a unique Big domain with a specific topology likely found in a broad range of other inverse autotransporters. The accumulated data allows us to model the complete passenger of intimin and propose functionality to the Big domains, D00–D0–D1, extending directly from the membrane.

Highlights

Enterohemorrhagic and enteropathogenic Escherichia coli are among the most important foodborne pathogens, posing a global health threat
The intimin passenger forms a rod-like extension consisting of four tandem bacterial immunoglobulin-like (Big) domains capped by a C-terminal C-type lectin-like domain (D3)
Crystal structure of the E. coli intimin subdomains D00–D0 exhibits an elongated conformation while D0–D1 shows a bent structure

Summary

Introduction

Enterohemorrhagic and enteropathogenic Escherichia coli are among the most important foodborne pathogens, posing a global health threat. Intimin consists of four extracellular bacterial immunoglobulin-like (Big) domains, D00–D2, extending into the fifth lectin subdomain (D3) that binds to the Tir-receptor on the host cell. Intimin is a 94 kDa outer membrane protein, essential for the intimate attachment of bacterial cells to the host cell surface, followed by actin pedestal formation[8]. The intimin passenger forms a rod-like extension consisting of four tandem bacterial immunoglobulin-like (Big) domains (subdomains D00–D0–D1–D2) capped by a C-terminal C-type lectin-like domain (D3). This architecture is similar to other inverse autotransporters, such as Yersinia pseudotuberculosis invasin[17]. D00 represents the first subdomain upon excretion, and its folding was hypothesized to provide the driving force for extracting the remaining Bigdomain in the intimin p assenger[16,19]

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Conclusion