1acc
From Proteopedia
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ANTHRAX PROTECTIVE ANTIGEN
Overview
Protective antigen (PA) is the central component of the three-part protein, toxin secreted by Bacillus anthracis, the organism responsible for, anthrax. After proteolytic activation on the host cell surface, PA forms a, membrane-inserting heptamer that translocates the toxic enzymes, oedema, factor and lethal factor, into the cytosol. PA, which has a relative, molecular mass of 83,000 (M(r) 83K), can also translocate heterologous, proteins, and is being evaluated for use as a general protein delivery, system. Here we report the crystal structure of monomeric PA at 2.1 A, resolution and the water-soluble heptamer at 4.5 A resolution. The monomer, is organized mainly into antiparallel beta-sheets and has four domains: an, amino-terminal domain (domain 1) containing two calcium ions and the, cleavage site for activating proteases; a heptamerization domain (domain, 2) containing a large flexible loop implicated in membrane insertion; a, small domain of unknown function (domain 3); and a carboxy-terminal, receptor-binding domain (domain 4). Removal of a 20K amino-terminal, fragment from domain 1 allows the assembly of the heptamer, a ring-shaped, structure with a negatively charged lumen, and exposes a large hydrophobic, surface for binding the toxic enzymes. We propose a model of pH-dependent, membrane insertion involving the formation of a porin-like, membrane-spanning beta-barrel.
About this Structure
1ACC is a Single protein structure of sequence from Bacillus anthracis with CA as ligand. The following page contains interesting information on the relation of 1ACC with [Anthrax Toxin]. Full crystallographic information is available from OCA.
Reference
Crystal structure of the anthrax toxin protective antigen., Petosa C, Collier RJ, Klimpel KR, Leppla SH, Liddington RC, Nature. 1997 Feb 27;385(6619):833-8. PMID:9039918
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