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Publication Abstract from PubMed

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 varphi-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 alpha-helix, permitting its extension to the varphi-clamp gate. This new mechanism of N-terminal unfolding is crucial for protein translocation.

Cryo-EM structures reveal translocational unfolding in the clostridial binary iota toxin complex.,Yamada T, Yoshida T, Kawamoto A, Mitsuoka K, Iwasaki K, Tsuge H Nat Struct Mol Biol. 2020 Mar;27(3):288-296. doi: 10.1038/s41594-020-0388-6. Epub, 2020 Mar 2. PMID:32123390^[1]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.