STRUCTURE OF TETANUS TOXIN - N-TERMINAL AMINO-ACID ANALYSIS OF THE 2 MOLECULAR-FORMS OF TETANUS TOXIN AND ITS COMPOSITE CHAINS

N-Terminal amino acid analysis of the intracellular form of tetanus toxin revealed proline as the single terminal residue present in significant quantities. In agreement with new concepts on the structure of tetanus toxin, a second N-terminal amino acid (leucine) was exposed upon conversion to the extracellular form of the toxin molecule. These results were corroborated by analysis of the separate polypeptide chains of the extracellular toxin, and it is concluded that the light chain polypeptide constitutes the N-terminal region of the single chain toxin molecule originally synthesized by the bacterial cell. Treatment of the intracellular tetanus toxin with trypsin in vitro resulted in the exposure of amino acids in addition to those found after conversion to the extracellular form effected by the bacterial protease during fermentation. © 1979.