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Structure and function of C-terminal catalytic region of Pasteurella multocida toxin

Pasteurella multocida toxin (PMT) is one of the virulence factors responsible for pathogenesis in some Pasteurellosis. We determined the crystal structure of the C-terminal region of PMT (C-PMT), which carries an intracellularly active moiety. The overall structure of C-PMT displays a Trojan horse structure, composed of three domains arranged in feet, body and head subunits with each linker loops, which were designated C1, C2, and C3 domains from the N- to C-terminus, respectively.

The C1 domain showing marked similarity in steric structure to the N-terminal domain of Clostridium difficile toxin B, was found to lead the toxin molecule to the plasma membrane. We found in the C3 domain the Cys-His-Asp catalytic triad that is organized only when the Cys is released from a disulfide bond. The steric alignment of the triad corresponded well to that of papain or other enzymes carrying the Cys-His-Asp triad. Our results indicate that PMT is an enzyme toxin carrying the cysteine protease-like catalytic triad dependent on the redox state, and functions oncytoplasmic face of the plasma membrane of target cells.

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Correspondence to Kengo Kitadokoro.

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Open Access This article is published under license to BioMed Central Ltd. This is an Open Access article is distributed under the terms of the Creative Commons Attribution 2.0 International License (, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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Kitadokoro, K., Kamitani, S., Fukui, A. et al. Structure and function of C-terminal catalytic region of Pasteurella multocida toxin. BMC Proc 2 (Suppl 1), P32 (2008).

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