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Crystal structure of the enzymatic component C2-I of the C2-toxin from Clostridium botulinum at pH 6.1
Structural highlights
FunctionEvolutionary Conservation Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf. Publication Abstract from PubMedC2 toxin from Clostridium botulinum is composed of the enzyme component C2-I, which ADP-ribosylates actin, and the binding and translocation component C2-II, responsible for the interaction with eukaryotic cell receptors and the following endocytosis. Three C2-I crystal structures at resolutions of up to 1.75 A are presented together with a crystal structure of C2-II at an appreciably lower resolution and a model of the prepore formed by fragment C2-IIa. The C2-I structure was determined at pH 3.0 and at pH 6.1. The structural differences are small, indicating that C2-I does not unfold, even at a pH value as low as 3.0. The ADP-ribosyl transferase activity of C2-I was determined for alpha and beta/gamma-actin and related to that of Iota toxin and of mutant S361R of C2-I that introduced the arginine observed in Iota toxin. The substantial activity differences between alpha and beta/gamma-actin cannot be explained by the protein structures currently available. The structure of the transport component C2-II at pH 4.3 was established by molecular replacement using a model of the protective antigen of anthrax toxin at pH 6.0. The C-terminal receptor-binding domain of C2-II could not be located but was present in the crystals. It may be mobile. The relative orientation and positions of the four other domains of C2-II do not differ much from those of the protective antigen, indicating that no large conformational changes occur between pH 4.3 and pH 6.0. A model of the C2-IIa prepore structure was constructed based on the corresponding assembly of the protective antigen. It revealed a surprisingly large number of asparagine residues lining the pore. The interaction between C2-I and C2-IIa and the translocation of C2-I into the target cell are discussed. Structure and action of the binary C2 toxin from Clostridium botulinum.,Schleberger C, Hochmann H, Barth H, Aktories K, Schulz GE J Mol Biol. 2006 Dec 8;364(4):705-15. Epub 2006 Sep 5. PMID:17027031[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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