Evolution and structure of two ADP‐ribosylation enterotoxins, Escherichia coli heat‐labile toxin and cholera toxin

Abstract

Nucleotide sequence comparisons of the heat‐labile enterotoxin (LTh) genes of E. coli pathogenic for humans with cholera toxin (CT) genes suggest that the two toxin genes have evolved from a common ancestry by a series of single selective base changes, while conserving the catalytic fragment A1 (ADP‐ribose transferase). Based on the local hydrophilicity profiles of LTh and CT peptides, a transmembrane segment appears to be present in A1 in both toxins.