The amino acids of Escherichia coli enterotoxin B subunit involved in binding to Bio-Gel A-5m or to the glycoprotein from mouse intestinal epithelial cells.
We determined whether Arg13, Met31, and Ser95 of the heat-labile enterotoxin B subunit (LT-B) might be involved in Lt-B binding to oligosaccharides, which did not bind to the B subunit of the cholera toxin (CT-B). Three LT-B mutants, R13H, M31L, and S95A were prepared by substituting three amino acid residues that differ in CT-B. These mutants formed a pentamer and exhibited the same binding ability to the GM1 ganglioside as native LT-B. Although these mutants did not bind to Bio-Gel A-5m, they did bind to the glycoprotein from mouse intestinal cells in the order R13H > M31L > S95A. These data suggest that Ser95, Met31, and Arg13 are important for LT-B binding to Bio-Gel A-5m, and that although Ser95 is also partially responsible for LT-B binding to the glycoprotein, Arg13 has no significant involvement in it.
Department of Microbiology, School of Medicine, Fujita Health University, Aichi, Japan.
H
H
Kawase
M
M
Kato
S
S
Imamura
T
T
Tsuji
A
A
Miyama
D000818:Animals; D002478:Cells, Cultured; D004591:Electrophoresis, Polyacrylamide Gel; D004768:Enterotoxins / Q000235:genetics* / Q000378:metabolism; D004847:Epithelial Cells; D004848:Epithelium / Q000737:chemistry; D004926:Escherichia coli / Q000235:genetics*; D005782:Gels / Q000378:metabolism; D006023:Glycoproteins / Q000378:metabolism; D007422:Intestines / Q000737:chemistry / Q000166:cytology; D007525:Isoelectric Focusing; D051379:Mice; D016297:Mutagenesis, Site-Directed; D009844:Oligosaccharides / Q000378:metabolism; D010957:Plasmids; D011485:Protein Binding / Q000235:genetics*
D004768:Enterotoxins; D005782:Gels; D006023:Glycoproteins; D009844:Oligosaccharides