1ikp
From Proteopedia
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Pseudomonas Aeruginosa Exotoxin A, P201Q, W281A mutant
Overview
Exotoxin A of Pseudomonas aeruginosa asserts its cellular toxicity through, ADP-ribosylation of translation elongation factor 2, predicated on binding, to specific cell surface receptors and intracellular trafficking via a, complex pathway that ultimately results in translocation of an enzymatic, activity into the cytoplasm. In early work, the crystallographic structure, of exotoxin A was determined to 3.0 A resolution, revealing a tertiary, fold having three distinct structural domains; subsequent work has shown, that the domains are individually responsible for the receptor binding, (domain I), transmembrane targeting (domain II), and ADP-ribosyl, transferase (domain III) activities, respectively. Here, we report the, structures of wild-type and W281A mutant toxin proteins at pH 8.0, refined, with data to 1.62 A and 1.45 A resolution, respectively. The refined, models clarify several ionic interactions within structural domains I and, II that may modulate an obligatory conformational change that is induced, by low pH. Proteolytic cleavage by furin is also obligatory for toxicity;, the W281A mutant protein is substantially more susceptible to cleavage, than the wild-type toxin. The tertiary structures of the furin cleavage, sites of the wild-type and W281 mutant toxins are similar; however, the, mutant toxin has significantly higher B-factors around the cleavage site, suggesting that the greater susceptibility to furin cleavage is due to, increased local disorder/flexibility at the site, rather than to, differences in static tertiary structure. Comparison of the refined, structures of full-length toxin, which lacks ADP-ribosyl transferase, activity, to that of the enzymatic domain alone reveals a salt bridge, between Arg467 of the catalytic domain and Glu348 of domain II that, restrains the substrate binding cleft in a conformation that precludes, NAD+ binding. The refined structures of exotoxin A provide precise models, for the design and interpretation of further studies of the mechanism of, intoxication.
About this Structure
1IKP is a Single protein structure of sequence from Pseudomonas aeruginosa with CL and NA as ligands. Full crystallographic information is available from OCA.
Reference
Refined crystallographic structure of Pseudomonas aeruginosa exotoxin A and its implications for the molecular mechanism of toxicity., Wedekind JE, Trame CB, Dorywalska M, Koehl P, Raschke TM, McKee M, FitzGerald D, Collier RJ, McKay DB, J Mol Biol. 2001 Dec 7;314(4):823-37. PMID:11734000
Page seeded by OCA on Tue Nov 20 17:28:34 2007
