6KLX

Pore structure of Iota toxin binding component (Ib)

Summary for 6KLX

• Entry DOI: 10.2210/pdb6klx/pdb
• EMDB information: 0721
• Descriptor: Iota toxin component Ib, CALCIUM ION (2 entities in total)
• Functional Keywords: bacterial binary toxin, protein translocation channel, adp-ribosylation, toxin
• Biological source: Clostridium perfringens
• Total number of polymer chains: 7
• Total formula weight: 521212.83

Authors

Yoshida, T.,Yamada, T.,Kawamoto, A.,Mitsuoka, K.,Iwasaki, K.,Tsuge, H. (deposition date: 2019-07-30, release date: 2020-01-15, Last modification date: 2024-03-27)

Primary citation

Yamada, T.,Yoshida, T.,Kawamoto, A.,Mitsuoka, K.,Iwasaki, K.,Tsuge, H.
Cryo-EM structures reveal translocational unfolding in the clostridial binary iota toxin complex.
Nat.Struct.Mol.Biol., 27:288-296, 2020

PubMed 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.

PubMed: 32123390
DOI: 10.1038/s41594-020-0388-6

Experimental method

ELECTRON MICROSCOPY (2.9 Å)