Dimeric form of diphtheria toxin: purification and characterization. Biochemistry 1986 May 06;25(9):2425-30
Date
05/06/1986Pubmed ID
3718959DOI
10.1021/bi00357a019Scopus ID
2-s2.0-0022511852 (requires institutional sign-in at Scopus site) 44 CitationsAbstract
Many preparations of diphtheria toxin were found to contain dimeric and multimeric toxin forms. The monomeric and dimeric forms were fractionated to greater than 98% purity, and their properties were compared. Dimeric toxin slowly dissociated to native monomers in solution at neutral pH and could be rapidly dissociated with dimethyl sulfoxide. In cell culture assays and rabbit skin tests, the dimer exhibited no significant toxic activity, except for that attributable to trace contamination by monomer, or partial dissociation to monomer during the incubation period. In guinea pig lethality tests, however, toxic activity varied depending upon the dose. At least 7-fold greater amounts of dimer than monomer (161 ng vs. 22 ng, respectively) were required to cause death at 18 h, whereas similar weights of the two toxin forms (22 ng) caused death at 120 h. This variability probably reflected slow dissociation of dimer to monomer in the animal. The dimer was unable to bind toxin receptors on the surface of susceptible cells, whereas it retained full activity in the ADP-ribosyltransferase, NAD-glycohydrolase, or ligand-binding assays. Thus, the lack of toxicity of the dimeric toxin may have resulted from distortion or occlusion of the receptor binding site on the B moiety. We propose that the dimer contains two monomeric units bound by hydrophobic interactions and that the points of contact involve regions of the B moieties that are normally buried in the native monomer.
Author List
Carroll SF, Barbieri JT, Collier RJAuthor
Joseph T. Barbieri PhD Professor in the Microbiology and Immunology department at Medical College of WisconsinMESH terms used to index this publication - Major topics in bold
AnimalsCarbon Radioisotopes
Chromatography, High Pressure Liquid
Diphtheria Antitoxin
Diphtheria Toxin
Guinea Pigs
Macromolecular Substances
NAD
Phosphorus Radioisotopes