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Science. 2005 Jul 29;309(5735):777-81.

A phenylalanine clamp catalyzes protein translocation through the anthrax toxin pore.

Author information

  • 1Department of Microbiology and Molecular Genetics, Harvard Medical School, 200 Longwood Avenue, Boston, MA 02115, USA.

Abstract

The protective antigen component of anthrax toxin forms a homoheptameric pore in the endosomal membrane, creating a narrow passageway for the enzymatic components of the toxin to enter the cytosol. We found that, during conversion of the heptameric precursor to the pore, the seven phenylalanine-427 residues converged within the lumen, generating a radially symmetric heptad of solvent-exposed aromatic rings. This "phi-clamp" structure was required for protein translocation and comprised the major conductance-blocking site for hydrophobic drugs and model cations. We conclude that the phi clamp serves a chaperone-like function, interacting with hydrophobic sequences presented by the protein substrate as it unfolds during translocation.

PMID:
16051798
[PubMed - indexed for MEDLINE]
PMCID:
PMC1815389
Free PMC Article
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