Purification and amino acid composition of type E botulinum neurotoxin

Abstract

The procedure we have adopted to purify type E botulinum neurotoxin (mol. wt. approximately 147,000) from bacterial cultures consistently yields a pure protein (a single band in polyacrylamide gel electrophoresis in the presence of sodium dodecylsulfate). Our procedure is a modification of one of the five published procedures. Other procedures have failed to yield pure neurotoxin. To develop reliable data on the amino acid composition, three batches of the neurotoxin were analyzed, each batch isolated from a separate neurotoxin producing culture. The best estimate of the number of amino acid residues per neurotoxin molecule was: Asp240 Thr75 Ser98 Glu118 Pro45 Gly58 Ala40 Val62 CyS7 Met17 Ile123 Leu107 Tyr70 Phe62 Lys97 His15 Arg34 Trp16.