title: Amino acid sequence homology between the enzymic domains of diphtheria toxin and Pseudomonas aeruginosa exotoxin A.
abstract: Despite similarities in their enzymic properties, diphtheria toxin (DT) and exotoxin A (ETA) of Pseudomonas aeruginosa have major differences in structure and action: consequently, the question of possible evolutionary relatedness of these two proteins remains unanswered. Here we report the existence of significant amino acid sequence homology between the enzymic domain of DT and that of ETA. Major segments of sequence may be aligned with high percentages of identity and of conservative substitutions. The homologous stretches in ETA form much of the active-site cleft in the X-ray crystallographic structure. This evidence implies that these domains, at least, have diverged from a common ancestral protein and that active-site residues have been strongly conserved.
mesh_terms: D036002:ADP Ribose Transferases; D000595:Amino Acid Sequence; D001427:Bacterial Toxins; D004167:Diphtheria Toxin / Q000235:genetics*; D005098:Exotoxins / Q000235:genetics*; D008958:Models, Molecular; D008969:Molecular Sequence Data; D011487:Protein Conformation; D011550:Pseudomonas aeruginosa / Q000235:genetics*; D012689:Sequence Homology, Nucleic Acid; D037521:Virulence Factors; D000097668:Pseudomonas aeruginosa Exotoxin A
chemical_list: D036002:ADP Ribose Transferases; D001427:Bacterial Toxins; D004167:Diphtheria Toxin; D005098:Exotoxins; D037521:Virulence Factors; D000097668:Pseudomonas aeruginosa Exotoxin A