Interaction ofVicia gramineaAnti-N Lectin with Cell Surface Glycoproteins from Erythrocytes with Rare Blood Group Antigens

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Abstract
Erythrocyte receptors for V. graminea (Vg) anti-N lectin were investigated after 125I-labeling of the purified lectin and binding to membrane components separated by dodecyl sulfate polyacrylamide gel electrophoresis. GP.alpha. (synonym glycophorin A or MN glycoprotein) and GP.delta. (synonym glycophorin B or Ss glycoprotein) are the main Vg receptors of native human blood group NN and MN erythrocytes whereas Vg lectin only binds to GP.delta. from MM red cells. The glycoprotein of 28 kDa [kilodaltons] present in Mi-III erythrocytes (a presumed variant of GP.delta.) carries Vg receptors. Both binding studies and agglutination experiments with this lectin suggest that the .delta.MiIII gene might produce more glycoprotein molecules than the normal .delta. gene. Binding of Vg lectin to hybrid glycoproteins [from MiV, St(at) and Dantu(+) donors] produced by unequal crossing-over between .alpha. and .delta. genes, may occur if the molecules exhibit N activity. The lectin does not bind to sialic acid- and glactose-deficient glycoproteins from Tn erythrocytes and no binding could be detected in the region of GP.delta. of erythrocytes from S-s-U-individuals. Addition of N-acetylgalactosamine residues to the alkali-labile oligosaccharides attached to GP.alpha. and GP.delta., as found in Cad erythrocytes, decrease the binding capacity for Vg lectin. The absence of Vg lectin binding sites on native GP.alpha. molecule from MgMg and McM erythrocytes, which carry well defined variants of this glycoprotein, supports the view that the binding site of the lectin on native glycoproteins is located at the N-terminal end of glycoprotein (GP.alpha. and GP.delta.) with N specificity (N-terminus = Leu).

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