title: Mapping the enzymatic active site of Pseudomonas aeruginosa exotoxin A.
abstract: Pseudomonas aeruginosa exotoxin A is a representative of a class of enzymes, the mono-ADP-ribosyl transferases, which catalyze the covalent transfer of an ADP-ribose moiety of NAD+ to a target substrate. Availability of the three-dimensional structure of exotoxin A provides the opportunity for mapping substrate binding sites and suggesting which amino acid residues may be involved in catalysis. Data from several sources have been combined to develop a proposal for the NAD+ binding site of exotoxin A: the binding of NAD+ fragments adenosine, AMP, and ADP have been delineated crystallographically to 6.0, 6.0, and 2.7 A, respectively; significant sequence homology spanning 60 residues has been found between exotoxin A and diphtheria toxin, which has the identical enzymatic activity; iodination of exotoxin A, under conditions in which only tyrosine 481 is iodinated in the enzymatic domain, abolishes ADP-ribosyl transferase activity.
authors.affiliation: Department of Chemistry and Biochemistry, University of Colorado, Boulder 80309.
authors.forename: B J
authors.initials: BJ
authors.lastname: Brandhuber
authors.forename: V S
authors.initials: VS
authors.lastname: Allured
authors.forename: T G
authors.initials: TG
authors.lastname: Falbel
authors.forename: D B
authors.initials: DB
authors.lastname: McKay
mesh_terms: D036002:ADP Ribose Transferases; D000595:Amino Acid Sequence; D001427:Bacterial Toxins; D001665:Binding Sites; D003461:Crystallography; D004167:Diphtheria Toxin / Q000032:analysis; D005098:Exotoxins / Q000032:analysis*; D005583:Fourier Analysis; D007455:Iodine; D008024:Ligands; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009243:NAD / Q000378:metabolism; D010449:Peptide Mapping; D011550:Pseudomonas aeruginosa / Q000201:enzymology*; D013774:Tetranitromethane; D037521:Virulence Factors; D000097668:Pseudomonas aeruginosa Exotoxin A
chemical_list: D036002:ADP Ribose Transferases; D001427:Bacterial Toxins; D004167:Diphtheria Toxin; D005098:Exotoxins; D007455:Iodine; D008024:Ligands; D009243:NAD; D013774:Tetranitromethane; D037521:Virulence Factors; D000097668:Pseudomonas aeruginosa Exotoxin A