Mar 4, 2020

Cryo-EM structures reveal translocational unfolding in the clostridial binary iota toxin complex

Nature Structural & Molecular Biology
Tomohito YamadaHideaki Tsuge

Abstract

The iota toxin produced by Clostridium perfringens type E is a binary toxin comprising two independent polypeptides: Ia, an ADP-ribosyltransferase, and Ib, which is involved in cell binding and translocation of Ia across the cell membrane. Here we report cryo-EM structures of the translocation channel Ib-pore and its complex with Ia. The high-resolution Ib-pore structure demonstrates a similar structural framework to that of the catalytic ϕ-clamp of the anthrax protective antigen pore. However, the Ia-bound Ib-pore structure shows a unique binding mode of Ia: one Ia binds to the Ib-pore, and the Ia amino-terminal domain forms multiple weak interactions with two additional Ib-pore constriction sites. Furthermore, Ib-binding induces tilting and partial unfolding of the Ia N-terminal α-helix, permitting its extension to the ϕ-clamp gate. This new mechanism of N-terminal unfolding is crucial for protein translocation.

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Mentioned in this Paper

Iota toxin, Clostridium perfringens
Plasma Membrane
Malignant Neoplasm of Ovary Stage Ia
EMILIN1 wt Allele
Polypeptides
Binding (Molecular Function)
PARP1 protein, human
Bacterial Toxins
ATP8a2 protein, mouse
Structure

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