Human erythrocyte membrane glycoproteins were solubilized and recovered in the aqueous phase after extraction of red cell ghosts with a mixture of chloroform and methanol. The major glycoprotein, the so-called MN glycoprotein, was prepared from this phase by gel filtration on Sepharose 4B columns in 6 M guanidine hydrochloride. By SDS-acrylamide gel electrophoresis the MN glycoproteins from the three major genetic types, MM, MN, and NN, were found to be relatively free from minor glycoprotein contaminants. The carbohydrate and amino acid composition did not reveal significant differences between the three MN genotypes. The specific activities of the purified glycoproteins were determined for inhibition of agglutinating anti-M and anti-N rabbit antisera and for inhibition of myxovirus hemagglutination. It was, furthermore, established that the purified MN glycoproteins contain a receptor for Phaseolus vulgaris phytohemagglutination. The red cell MN glycoprotein inhibits partially lymphocyte stimulation induced by unfractionated Phaseolus vulgaris phytohemagglutinin; the red cell MN glycoprotein does not influence the lymphocyte stimulation induced by purified Phaseolus vulgaris mitogen.

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