Essential Role of Histidine Peptides in Tetanus Toxin Production

SUMMARY A pancreatic digest of casein, the key material in a defined medium for the production of tetanus toxin, has been separated by means of reversible resin columns into three main fractions: (1) an acidic fraction, (2) a neutral fraction, and (3) a basic fraction. The part,icipation of the basic fraction in the production of toxin has now been elucidated. By means of silver precipitation it has been separated into three subfractions; free arginine and lysine will substitute for the corresponding two subfractions, and the essential component in the histidine fract,ion has been identified as histidine in peptide linkage. Synthetic histidine peptides can be successfully sub- stituted for the naturally occurring material, and differences in their effect on toxin production have been observed. Glycyl-L-histidine and a-amino- n-butyryl-L-histidine mere the most active of those tested. Carnosine or acetylhistidine will substitute, but good toxin is produced only when large amounts of these substances are used. Free L-histidine is without effect on toxin production but will support growth of the organism. Preliminary experiments on the remaining unknown components in the acidic and neu- tral fractions indicate that they also may be pept.ide in nature.