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- Title
Glycan-dependent cell adhesion mechanism of Tc toxins.
- Authors
Roderer, Daniel; Bröcker, Felix; Sitsel, Oleg; Kaplonek, Paulina; Leidreiter, Franziska; Seeberger, Peter H.; Raunser, Stefan
- Abstract
Toxin complex (Tc) toxins are virulence factors of pathogenic bacteria. Tcs are composed of three subunits: TcA, TcB and TcC. TcA facilitates receptor–toxin interaction and membrane permeation, TcB and TcC form a toxin-encapsulating cocoon. While the mechanisms of holotoxin assembly and pore formation have been described, little is known about receptor binding of TcAs. Here, we identify heparins/heparan sulfates and Lewis antigens as receptors for different TcAs from insect and human pathogens. Glycan array screening reveals that all tested TcAs bind negatively charged heparins. Cryo-EM structures of Morganella morganii TcdA4 and Xenorhabdus nematophila XptA1 reveal that heparins/heparan sulfates unexpectedly bind to different regions of the shell domain, including receptor-binding domains. In addition, Photorhabdus luminescens TcdA1 binds to Lewis antigens with micromolar affinity. Here, the glycan interacts with the receptor-binding domain D of the toxin. Our results suggest a glycan dependent association mechanism of Tc toxins on the host cell surface. Although Tc toxins are a major class of bacterial toxin translocation systems, little is known about their receptor binding. Here, the authors identify heparins/heparan sulfates and Lewis antigens as receptors for different Tc toxins, determine cryo-EM structures of three toxin-glycan complexes and propose a two-step cell adhesion mechanism for Tc toxins.
- Subjects
BACTERIAL toxins; GLYCANS; TOXINS; ANTIGEN receptors; PHOTORHABDUS luminescens; HEPARAN sulfate; INSECT pathogens
- Publication
Nature Communications, 2020, Vol 11, Issue 1, p1
- ISSN
2041-1723
- Publication type
Article
- DOI
10.1038/s41467-020-16536-7