title: The role of histidine residues in the alpha toxin of Clostridium perfringens.
abstract: The alpha-toxin (phospholipase C) of Clostridium perfringens has been reported to contain catalytically essential zinc ions. We report here that histidine residues are essential for the co-ordination of these ion(s). Incubation of alpha toxin with diethylpyrocarbonate, a histidine modifying reagent, did not result in the loss of phospholipase C activity unless the protein was first incubated with EDTA, suggesting that zinc ions normally protect the susceptible histidine residues. When the amino acid sequences of three phospholipase C's were aligned, essential zinc binding histidine residues in the non-toxic B. cereus phospholipase C were found in similar positions in the toxic C. perfringens enzyme and the weakly toxic C. bifermentans phospholipase C.
authors.affiliation: Chemical Defence Establishment, Salisbury, Wilts, U.K.
authors.forename: R W
authors.initials: RW
authors.lastname: Titball
authors.forename: T
authors.initials: T
authors.lastname: Rubidge
mesh_terms: D000595:Amino Acid Sequence; D001427:Bacterial Toxins / Q000037:antagonists & inhibitors / Q000378:metabolism*; D002135:Calcium-Binding Proteins; D003016:Clostridium perfringens / Q000201:enzymology*; D004047:Diethyl Pyrocarbonate / Q000494:pharmacology; D004492:Edetic Acid / Q000494:pharmacology; D006639:Histidine / Q000378:metabolism*; D006898:Hydroxylamines / Q000494:pharmacology; D008969:Molecular Sequence Data; D012689:Sequence Homology, Nucleic Acid; D010738:Type C Phospholipases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D015032:Zinc / Q000378:metabolism*
chemical_list: D001427:Bacterial Toxins; D002135:Calcium-Binding Proteins; D006898:Hydroxylamines; D006639:Histidine; D004492:Edetic Acid; D010738:Type C Phospholipases; C040649:alpha toxin, Clostridium perfringens; D015032:Zinc; D004047:Diethyl Pyrocarbonate