The elemental and amino acid composition of crystalline Clostridium botulinum type A toxin.

The isolation of Clostridium botulinurn type A toxin in crystalline form (1, 2) has led to an interest in its chemical composition. An apparently complete analysis of the pure crystalline toxin is presented in this paper. Preliminary studies have indicated that the toxin is a protein with an isoelectric point of pH 5.6, possessing the properties of a globulin (l-3). It is free from carbohydrate, halogens, iron, manganese, and magnesium. In addition to carbon, hydrogen, oxygen, nitrogen, and sulfur it contains a small amount of phosphorus and a negligible amount of ash. Nineteen amino acids have been found. The criteria of purity for the crystalline toxin used in this work are as follows: (1) Ultracentrifugation (4) and electrophoretic studies (1, 2) showed the toxin to be a homogeneous substance. (2) Separately prepared batches of toxin produced under similar cultural conditions showed constant values for the fourteen amino acids determined as an aid in studies of the constancy of composition. (3) Serologically, the toxin acts as a single substance in the toxin-antitoxin reaction. The material used for these studies was prepared by the method of Lamanna and coworkers (1).