Postnatal changes in lectin binding to microvillus membranes from rat intestine.

The intestinal microvillus membrane of suckling rats has a large number of unsubstituted and sialyl-substituted sites for 125I-labeled peanut agglutinin in glycopeptides, indicating that the membrane surface is rich in beta, D-Gal(1 leads to 3)D-GalNAc residues. The membrane loses all the unsubstituted and about half of the sialyl-substituted PNA-reactive sites during weaning. Simultaneously, there occur increases in the bindings of 125I-labeled soybean lectin and 125I-Ricinus communis toxin to unsubstituted sites in glycopeptides. This indicates appearance of new terminal nonreducing D-GalNAc and D-Gal in glycopeptides in the mature membranes. The developmental loss of PNA reactive sites from the microvillus membrane in rat intestine is probably related to D-GalNAc substitution in O-glycans of mucin-type glycoproteins, and to steric hindrance arising in the course of glycosylation.