Revised amino acid sequence for a heat-stable enterotoxin produced by an Escherichia coli strain (18D) that is pathogenic for humans

Abstract

The amino acid sequence of heat-stable enterotoxin produced by enterotoxigenic Escherichia coli 18D has been revised. Amino acids originally assigned to positions 11 and 18, i.e., Tyr and Asn, respectively, were found to occupy positions 18 and 11, respectively. Thus all heat-stable enterotoxins composed of 18 amino acids sequenced to date from human, porcine, and bovine isolates of E. coli have identical primary structures, i.e., Asn-Thr-Phe-Tyr-Cys-Cys-Glu-Leu-Cys-Cys-Asn-Pro-Ala-Cys-Ala-Gly-Cys-Tyr. Furthermore, all 18- and 19-amino-acid heat-stable enterotoxins from E. coli share an almost identical core sequence, i.e., 14 of the 15 carboxy-terminal amino acid residues are identical.