Abstract
Glycolipids were prepared from epithelial cells of the small intestine of a newborn calf and assayed for Escherichia coli K99 binding activity on thin-layer chromatograms and in microtiter wells. The bacteria did not bind to any of the non-acid glycolipids, while in the acid fraction several binding-positive glycolipids were detected. The acid glycolipids were isolated and characterized by mass spectrometry, proton NMR spectroscopy and other methods. The following gangliosides were identified, mainly from the epithelial cells from the upper part of the small intestine: NeuAcα2-3Galβ1-4G1cβ1-Cer (NeuAc-GM3), NeuGcα2-3Galβ1-4Glcβl-Cer (NeuGc-GM3), Ga1NAcβ1-4(NeuGca2-3)Galβ1-4G1cβ1-Cer (NeuGc-GM2), Galβl-3Ga1NAcβ1-4(NeuGcα2-3)Gal β1-4GIcβ1-Cer (NeuGc-GM1), and NeuGcα2-3Galβ1-3Ga1NAcf31-4(NeuGcα2-3)Galβ1-4G1cβ1-Cer (NeuGc-GDla). A positive binding was demonstrated to NeuGc-GM3, NeuGc-GM2, and NeuGc-GDla, while NeuAc-GM3 and NeuGc-GM1 were negative. The binding pattern differed somewhat for total acid glycolipids of epithelial cells from three different parts of the small intestine. Based on binding preferences of E. coli K99 to a number of glycolipids of various origins, in comparison with calculated minimum energy conformations, a binding epitope was delineated.
