Structural highlights
Function
[TOXA_PSEAE] An NAD-dependent ADP-ribosyltransferase (ADPRT). Catalyzes the transfer of the ADP ribosyl moiety of oxidized NAD (NAD(+)) onto eukaryotic elongation factor 2 (eEF-2) thus arresting protein synthesis. Has an LD(50) of 65 ng/ml against the human lung epithelial cell line C38.[1]
Publication Abstract from PubMed
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.
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[2]
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.
See Also
References
- ↑ Jorgensen R, Purdy AE, Fieldhouse RJ, Kimber MS, Bartlett DH, Rod Merrill A. Cholix toxin, a novel ADP-ribosylating factor from vibrio cholerae. J Biol Chem. 2008 Feb 25;. PMID:18276581 doi:M710008200
- ↑ Wedekind JE, Trame CB, Dorywalska M, Koehl P, Raschke TM, McKee M, FitzGerald D, Collier RJ, McKay DB. Refined crystallographic structure of Pseudomonas aeruginosa exotoxin A and its implications for the molecular mechanism of toxicity. J Mol Biol. 2001 Dec 7;314(4):823-37. PMID:11734000 doi:10.1006/jmbi.2001.5195
