title: Guanidination and nitroguanidination of staphylococcal enterotoxin B.
abstract: Guanidination of the free amino groups of staphylococcal enterotoxin B with 3,5-dimethyl-1-guanylpyrazole converted 31-32 of 33 epsilon-amino groups and 30% of the N-terminal residue. This product, although markedly reduced in solubility, suffered no gross change in conformation and retained full biological activity. A derivative prepared by reaction with O-methylisourea with only one lysyl residue unaltered lost most of its emetic activity. Nitroguanidination with 3,5-dimethyl-1-nitroguanylpyrazole converted up to 28 of the epsilon-amino groups and essentially all of the N-terminus. This material was greatly reduced in ability to produce emesis and like the O-methylisourea prepared guanidinated enterotoxin, gave only a line of partial identity in double diffusion. The loss of activity is attributed to unfolding and it is concluded that the free amino groups of enterotoxin B do not critically participate in either its antigenic determinants or its active center for emesis.
authors.affiliation: Biological Sciences Laboratories, Fort Detrick, Frederick, Md. 21701, USA.
authors.forename: L
authors.initials: L
authors.lastname: Spero
authors.forename: H M
authors.initials: HM
authors.lastname: Jacoby
authors.forename: J E
authors.initials: JE
authors.lastname: Dalidowicz
authors.forename: S J
authors.initials: SJ
authors.lastname: Silverman
mesh_terms: D000345:Affinity Labels; D000578:Amidines; D000818:Animals; D004768:Enterotoxins / Q000737:chemistry* / Q000633:toxicity; D018698:Glutamic Acid / Q000737:chemistry; D005779:Immunodiffusion; D007202:Indicators and Reagents; D007700:Kinetics; D007928:Lethal Dose 50; D008782:Methylurea Compounds; D013211:Staphylococcus aureus; D018089:Superantigens / Q000737:chemistry
chemical_list: D000345:Affinity Labels; D000578:Amidines; D004768:Enterotoxins; D007202:Indicators and Reagents; D008782:Methylurea Compounds; D018089:Superantigens; C005993:3,5-dimethylpyrazole-1-carboxamidine; C002249:O-methylisourea; C031818:enterotoxin B, staphylococcal; D018698:Glutamic Acid