title: Analysis of tryptophan-rich region in Clostridium septicum alpha-toxin involved with binding to glycosylphosphatidylinositol-anchored proteins.
abstract: Clostridium septicum alpha-toxin has a unique tryptophan-rich region ((302)NGYSEWDWKWV(312)) that consists of 11 amino acid residues near the C-terminus. Using mutant toxins, the contribution of individual amino acids in the tryptophan-rich region to cytotoxicity and binding to glycosylphosphatidylinositol (GPI)-anchored proteins was examined. For retention of maximum cytotoxic activity, W307 and W311 are essential residues and residue 309 has to be hydrophobic and possess an aromatic side chain, such as tryptophan or phenylalanine. When residue 308, which lies between tryptophans (W307 and W309) is changed from an acidic to a basic amino acid, the cytotoxic activity of the mutant is reduced to less than that of the wild type. It was shown by a toxin overlay assay that the cytotoxic activity of each mutant toxin correlates closely with affinity to GPI-anchored proteins. These findings indicate that the WDW_W sequence in the tryptophan-rich region plays an important role in the cytotoxic mechanism of alpha-toxin, especially in the binding to GPI-anchored proteins as cell receptors.
authors.affiliation: Laboratory of Veterinary Epidemiology, Department of Veterinary Science, Graduate School of Life and Environmental Sciences, Osaka Prefecture University, 1-58 Rinku Orai-kita, Izumisano, Osaka, 598-8531, Japan. mukamoto@vet.osakafu‐u.ac.jp
authors.forename: Masafumi
authors.initials: M
authors.lastname: Mukamoto
authors.forename: Ryota
authors.initials: R
authors.lastname: Kimura
authors.forename: Mudenda B
authors.initials: MB
authors.lastname: Hang'ombe
authors.forename: Tomoko
authors.initials: T
authors.lastname: Kohda
authors.forename: Shunji
authors.initials: S
authors.lastname: Kozaki
mesh_terms: D000818:Animals; D001427:Bacterial Toxins / Q000235:genetics / Q000378:metabolism* / Q000633:toxicity*; D002470:Cell Survival / Q000187:drug effects; D002522:Chlorocebus aethiops; D052557:Clostridium septicum / Q000235:genetics / Q000378:metabolism*; D004252:DNA Mutational Analysis; D017261:Glycosylphosphatidylinositols / Q000378:metabolism*; D050505:Mutant Proteins / Q000235:genetics / Q000378:metabolism / Q000633:toxicity; D011485:Protein Binding; D011506:Proteins / Q000378:metabolism*; D014364:Tryptophan / Q000235:genetics / Q000378:metabolism*; D014709:Vero Cells
chemical_list: D001427:Bacterial Toxins; D017261:Glycosylphosphatidylinositols; D050505:Mutant Proteins; D011506:Proteins; C064270:hemolytic toxin, Clostridium septicum; D014364:Tryptophan