title: Arrangement of disulfide bridges and positions of sulfhydryl groups in tetanus toxin.
abstract: Tetanus toxin is a 151-kDa protein. The complete amino acid sequence is known. The mature toxin is made up of two peptide chains and contains 10 half-cystine residues. Treatment with 4-vinylpyridine in the presence of 6 M guanidine converted six of them into S-pyridylethyl cysteine residues as determined by amino acid analysis. When alkylation was preceded by mercaptolysis, all 10 half-cystine residues were recovered in the S-pyridylethylated form. It was therefore concluded that the toxin contains six sulfhydryl groups and two disulfide bonds. The positions of the residues carrying sulfhydryl groups and of those involved in disulfide bridges were determined by labelling of the toxin alternatively with 4-vinylpyridine or with 4-dimethylaminoazobenzene-4'-iodoacetamide (DABIA), directly or after mercaptolysis. The toxin derivatives were cleaved with cyanogen bromide and the elution patterns in reversed-phase HPLC compared. The chromatography components were identified by N-terminal amino acid sequence and amino acid composition. In the chromatography of the non-mercaptolysed, DABIA-treated sample four chromophore-carrying components were detected which could be demonstrated by N-terminal sequence analysis to correspond to six half-cystine-containing cyanogen bromide fragments. In the mercaptolysed, DABIA-treated sample three additional chromophore-carrying components were present, corresponding to two previously disulfide-linked cyanogen bromide fragments and one fragment which had contained an internal disulfide bridge. The HPLC patterns showed characteristic differences as the DABIA-labelled fragments were considerably more hydrophobic than the corresponding vinylpyridine-labelled fragments. It was established that the half-cystine residues in positions 26, 185, 198, 311, 868, and 1300 are present in the sulfhydryl form, that those in positions 438 and 466 are disulfide-bridged, thereby connecting the light and heavy chains of the toxin, and that those in positions 1076 and 1092 are disulfide-bridged, thereby giving rise to a loop in the heavy chain. During the progress of the investigations about 20% of the amino acid sequence previously predicted from DNA analysis was confirmed by protein-chemical methods.
authors.affiliation: Max-Planck-Institut für Biochemie, Martinsried bei München, Federal Republic of Germany.
authors.forename: K
authors.initials: K
authors.lastname: Krieglstein
authors.forename: A
authors.initials: A
authors.lastname: Henschen
authors.forename: U
authors.initials: U
authors.lastname: Weller
authors.forename: E
authors.initials: E
authors.lastname: Habermann
mesh_terms: D000595:Amino Acid Sequence; D000596:Amino Acids / Q000032:analysis; D002851:Chromatography, High Pressure Liquid; D003488:Cyanogen Bromide; D003545:Cysteine; D003553:Cystine; D004220:Disulfides / Q000032:analysis*; D007202:Indicators and Reagents; D008969:Molecular Sequence Data; D010446:Peptide Fragments / Q000302:isolation & purification; D011725:Pyridines; D013438:Sulfhydryl Compounds / Q000032:analysis*; D013744:Tetanus Toxin / Q000032:analysis*; D004124:p-Dimethylaminoazobenzene / Q000031:analogs & derivatives
chemical_list: D000596:Amino Acids; D004220:Disulfides; D007202:Indicators and Reagents; D010446:Peptide Fragments; D011725:Pyridines; D013438:Sulfhydryl Compounds; D013744:Tetanus Toxin; D003553:Cystine; C038560:4-dimethylaminoazobenzene-4'-iodoacetamide; D004124:p-Dimethylaminoazobenzene; C029351:4-vinylpyridine; D003545:Cysteine; D003488:Cyanogen Bromide