The chain composition of tetanus toxin.

Although tetanus toxins from cell and culture filtrate appear indistinguishable by several criteria, only the filtrate toxin can be cleaved into two chains by disulfide scission. These chains approximate molecular weights of 95,000 and 55,000. Determinations of sulfhydryl groups and total half-cystine residues for both the cell and filtrate toxins gave values of approximately six and nine, respectively and in filtrate toxin the half-cystine residues are found evenly distributed between the two chains.