title: Sequence of heat-labile enterotoxin of Escherichia coli pathogenic for humans.
abstract: We determined the complete nucleotide sequence of the toxB gene (375 base pairs in length), which encodes the B subunit of heat-labile enterotoxin produced from Escherichia coli pathogenic for humans (hLT). The amino acid sequence of the B subunit of hLT was deduced from the nucleotide sequence. Consequently, it has become possible to study the homology between the B subunits of three similar toxins: hLT, LT produced from E. coli pathogenic for piglets (pLT), and cholera toxin (the latter two sequences have been reported by others). The three B subunits are all 103 amino acids in length. A comparison of the toxB gene and the eltB gene, which encodes the B subunit of pLT, showed a 98% homology at the nucleotide level and a 95% homology at the amino acid (of a precursor) level, indicating the possibility that the two genes share a common ancestor. With respect to the B-subunit sequences, the homologies between hLT and pLT, between hLT and cholera toxin, and between pLT and cholera toxin were 96, 81, and 79%, respectively. Several large common sequences are conserved by the three peptides. In contrast, no sequences are present in both pLT and cholera toxin but missing in hLT.
mesh_terms: D000595:Amino Acid Sequence; D001427:Bacterial Toxins; D001483:Base Sequence; D002772:Cholera Toxin / Q000235:genetics; D004768:Enterotoxins / Q000235:genetics*; D004926:Escherichia coli / Q000235:genetics*; D029968:Escherichia coli Proteins; D005798:Genes, Bacterial; D009876:Operon; D014176:Protein Biosynthesis
chemical_list: D001427:Bacterial Toxins; D004768:Enterotoxins; D029968:Escherichia coli Proteins; D002772:Cholera Toxin; C027538:heat-labile enterotoxin, E coli