Characterisation of the binding sites for Escherichia coli heat-labile toxin type I in intestinal brush borders

Biochim Biophys Acta. 1991 Oct 10;1075(2):154-61. doi: 10.1016/0304-4165(91)90246-d.


Intestinal brush borders from Wistar rats contained a total of 20-30-times more binding sites for Escherichia coli heat-labile enterotoxin (LT-1) than for cholera toxin (CT). The results suggest that LT-1 binds to sites in addition to ganglioside GM1, the binding site for CT. Brush border proteins were separated by SDS-PAGE, blotted to nitrocellulose and the filters incubated with 125I-labeled toxins. [125I]LT-1 was shown to bind to a series of brush border galactoproteins ranging in size from 130-140 kDa. Binding was inhibited by unlabeled LT-1 (but not CT), and by ricin and free galactose. A number of brush border enzymes are large glycoproteins which can be solubilised by papain. The papain-solubilised sucrase-isomaltase complex was purified by affinity chromatography and shown to bind LT-1, as did the proteins in fractions enriched in maltase activity. However, such brush border galactoproteins do not account for all of the additional LT-1 binding sites. Thus, brush borders prepared from 1-15-day-old rabbits contained many more binding sites for LT-1 than CT despite the absence of any sucrase-isomaltase activity, and no [125I]LT-1 binding proteins could be detected by blotting. There was a marked variation in the number of LT-1 binding sites in different strains of rat, and between different species.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Bacterial Toxins / chemistry*
  • Binding Sites
  • Cholera Toxin / chemistry
  • Dogs
  • Enterotoxins / chemistry*
  • Escherichia coli / chemistry*
  • Escherichia coli Proteins*
  • Glycoproteins / chemistry
  • Humans
  • Intestine, Small / enzymology
  • Intestine, Small / ultrastructure
  • Microvilli / chemistry*
  • Microvilli / enzymology
  • Rats
  • Rats, Inbred Strains
  • Species Specificity
  • Sucrase-Isomaltase Complex / isolation & purification


  • Bacterial Toxins
  • Enterotoxins
  • Escherichia coli Proteins
  • Glycoproteins
  • galactoproteins
  • Cholera Toxin
  • heat-labile enterotoxin, E coli
  • Sucrase-Isomaltase Complex