Specificity of the sialic acid-binding lectin from the snail Cepaea hortensis.
The specificity of the sialic acid-binding lectin from the snail Cepaea hortensis, purified by affinity chromatography on fetuin-Sepharose, was studied by hemagglutination inhibition assay applying 32 sialic acid derivatives and 14 glycoproteins. 2-alpha-Methyl-9-O-acetyl-NeuAc was the most potent inhibitor, followed closely by 2-alpha-methyl-NeuAc and 2-alpha-benzyl-NeuAc. An axially orientated carboxyl group is a prerequisite for maximal lectin-sugar binding. Neither size nor polarity of the alpha-anomeric substituent significantly influenced inhibition potency. An intact sialic acid N-acetyl group is essential for optimal lectin-sugar interaction. The trihydroxypropyl side chain also is of great importance. However, a bulky hydrophobic substituent at the side chain like a 9-O-tosyl residue did not decrease binding to the lectin. The lectin did not distinguish between NeuAc alpha 2----3Gal beta 1----4Glc and NeuAc alpha 2----6Gal beta 1----4Glc. Among other sugars tested, only N-acetylglucosamine showed inhibition, although 50-fold less. The most potent glycoprotein inhibitors were those carrying O-chains only or preferentially, as ovine submaxillary mucin, bovine submaxillary mucin, and glycophorin A. Tamm-Horsfall protein was an exception being a strong inhibitor, although carrying only N-chains. Asialoglycoproteins were inactive. Glycoproteins containing the NeuAc alpha 2----3Gal sequence inhibited the lectin as well as those with NeuAc alpha 2----6GalNAc. From the results a model of the lectin's binding site for sialic acid is suggested.
Brossmer
R
R
Institute of Biochemistry II, University of Heidelberg, Federal Republic of Germany.
Wagner
M
M
Fischer
E
E
D000818:Animals; D006023:Glycoproteins / Q000378:metabolism; D006386:Hemagglutination Tests; D006801:Humans; D037102:Lectins / Q000378:metabolism*; D009844:Oligosaccharides / Q000378:metabolism; D063265:Sialic Acid Binding Immunoglobulin-like Lectins; D012794:Sialic Acids / Q000378:metabolism*; D012908:Snails; D013379:Substrate Specificity
D006023:Glycoproteins; D037102:Lectins; D009844:Oligosaccharides; D063265:Sialic Acid Binding Immunoglobulin-like Lectins; D012794:Sialic Acids