Interaction of mistletoe toxic lectin- I with sialoglycoproteins

Journal/Book: Biochem. Biophys. Res. Com. 214 (2), 396-402. 1995;

Abstract: The binding properties of mistletoe toxic lectin-I (ML-I) with sialo-N-and O-glycans were investigated by quantitative precipitin andprecipitin inhibition assays. Human alpha 1-acid glycoprotein reactedstrongly with ML-I, precipitating over 82% of the lectin nitrogentested, while the precipitability of its asialo product decreased by30%. Native fetuin precipitated 50% of the ML-I added, and itsreactivity was reduced by 20% after desialylation. On the contrary, thepoor reactivity of rat sublingual sialoglycoprotein with ML-I increasedsubstantially after removal of sialic acid and completely precipitatedthe lectin added. The glycoprotein-lectin interactions were inhibited byNeuAc alpha 2--> 3/alpha 2--> 6Gal beta 1--> 4Glc and/or Gal beta 1--> 4Glc(NAc) residues. From the above results, it is concluded that ML-I isspecific for sialic acid. However, sialic acid of some O-glycans alsoacts as masking molecule as the precipitability of rat sublingual andbovine submandibular glycoproteins with ML-I increased afterdesialylation. Author.

Keyword(s): ALPHA-FETOPROTEINS

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