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.
Publication types
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Research Support, Non-U.S. Gov't
MeSH terms
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ADP Ribose Transferases / chemistry*
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ADP Ribose Transferases / genetics
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ADP Ribose Transferases / metabolism
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Amino Acid Sequence
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Antigens, Bacterial / chemistry*
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Antigens, Bacterial / genetics
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Antigens, Bacterial / metabolism
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Bacterial Toxins / chemistry*
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Bacterial Toxins / genetics
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Bacterial Toxins / metabolism
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Binding Sites
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Cloning, Molecular
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Clostridium perfringens / chemistry*
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Clostridium perfringens / genetics
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Clostridium perfringens / metabolism
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Clostridium perfringens / pathogenicity
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Cryoelectron Microscopy
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Crystallography, X-Ray
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Escherichia coli / genetics
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Escherichia coli / metabolism
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Gene Expression
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Genetic Vectors / chemistry
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Genetic Vectors / metabolism
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Models, Molecular
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Protein Binding
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Protein Conformation, alpha-Helical
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Protein Conformation, beta-Strand
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Protein Interaction Domains and Motifs
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Protein Multimerization
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Protein Subunits / chemistry*
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Protein Subunits / genetics
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Protein Subunits / metabolism
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Protein Transport
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Recombinant Proteins / chemistry
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Recombinant Proteins / genetics
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Recombinant Proteins / metabolism
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Sequence Alignment
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Sequence Homology, Amino Acid
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Substrate Specificity
Substances
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Antigens, Bacterial
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Bacterial Toxins
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Protein Subunits
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Recombinant Proteins
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anthrax toxin
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iota toxin, Clostridium perfringens
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ADP Ribose Transferases