New procedures for glycophorin A purification with high yield and high purity

Glycophorin A (GPA) is the major glycoprotein of the human erythrocyte membrane. It is known to form, in SDS gels as well as in a membrane environment, homodimers, and also heterodimers with the homologous molecule Glycophorin B (GPB). It is shown in this report that the propensity of GPA to dimerize with GPB precludes satisfactory preparation with high yield of pure GPA using classical techniques including SEC and RPLC. It was demonstrated using multiple angle light scattering that GPA is eluted from RPLC columns as dimers. A convenient procedure was devised which allowed us to get pure GPA with high yield. This procedure consists of selectively blocking GPA-GPB heterodimer formation by selective modification of Cysteine 50 of GPB before RPLC.