Refined Crystallographic Structure of Pseudomonas aeruginosa Exotoxin A and its Implications for the Molecular Mechanism of Toxicity

摘要: Exotoxin A of Pseudomonas aeruginosa asserts its cellular toxicity through ADP-ribosylation translation elongation factor 2, predicated on binding to specific cell surface receptors and intracellular trafficking via a complex pathway that ultimately results in translocation an enzymatic activity into the cytoplasm. In early work, crystallographic structure exotoxin was determined 3.0 resolution, revealing tertiary fold having three distinct structural domains; subsequent work has shown domains are individually responsible for receptor (domain I), transmembrane targeting II), ADP-ribosyl transferase III) activities, respectively. Here, we report structures wild-type W281A mutant toxin proteins at pH 8.0, refined with data 1.62 1.45 The models clarify several ionic interactions within I II may modulate obligatory conformational change is induced by low pH. Proteolytic cleavage furin also toxicity; protein substantially more susceptible than toxin. sites W281 toxins similar; however, significantly higher B-factors around site, suggesting greater susceptibility due increased local disorder/flexibility rather differences static structure. Comparison full-length toxin, which lacks activity, domain alone reveals salt bridge between Arg467 catalytic Glu348 restrains substrate cleft conformation precludes NAD+ binding. provide precise design interpretation further studies mechanism intoxication.