title: Analysis of receptor-binding site in Escherichia coli enterotoxin.
abstract: Heat-labile enterotoxin produced by enterotoxigenic Escherichia coli and cholera enterotoxin are both composed of A and B subunits. The A subunit is an enzymatically active ADP-ribosylating subunit, while the B subunit, consisting of 103 amino acids, binds the toxin to a receptor, GM1-ganglioside, on the cell surface. A mutant isolated after treatment of E. coli producing heat-labile enterotoxin with N-methyl-N'-nitro-N-nitrosoguanidine produces a B subunit that is unable to bind to ganglioside. This subunit was purified and its primary amino acid sequence was determined. It differed from the native B subunit in only one amino acid at position 33; namely it had aspartate instead of glycine at position 33 from the N terminus. Thus glycine at position 33 from the N terminus of the B subunit is important for binding the B subunit to the ganglioside receptor.
mesh_terms: D000246:Adenosine Diphosphate Ribose / Q000378:metabolism; D000595:Amino Acid Sequence; D000596:Amino Acids / Q000032:analysis; D000818:Animals; D001427:Bacterial Toxins / Q000378:metabolism*; D002460:Cell Line; D002772:Cholera Toxin / Q000378:metabolism; D002851:Chromatography, High Pressure Liquid; D002918:Chymotrypsin / Q000378:metabolism; D002942:Circular Dichroism; D006224:Cricetinae; D003412:Cricetulus; D004768:Enterotoxins / Q000378:metabolism*; D004797:Enzyme-Linked Immunosorbent Assay; D004926:Escherichia coli / Q000235:genetics; D029968:Escherichia coli Proteins; D005260:Female; D005677:G(M1) Ganglioside / Q000378:metabolism*; D005732:Gangliosides / Q000378:metabolism*; D005779:Immunodiffusion; D007526:Isoelectric Point; D046911:Macromolecular Substances; D009154:Mutation; D010053:Ovary / Q000378:metabolism; D013056:Spectrophotometry, Ultraviolet; D013552:Swine
chemical_list: D000596:Amino Acids; D001427:Bacterial Toxins; D004768:Enterotoxins; D029968:Escherichia coli Proteins; D005732:Gangliosides; D046911:Macromolecular Substances; D000246:Adenosine Diphosphate Ribose; D005677:G(M1) Ganglioside; D002772:Cholera Toxin; C027538:heat-labile enterotoxin, E coli; D002918:Chymotrypsin