INTERACTION OF PROTEIN-4.1 WITH THE RED-CELL MEMBRANE - EFFECTS OF PHOSPHORYLATION BY PROTEIN-KINASE-C

Phosphorylation with endogenous protein kinase C causes the membrane s keletal protein, band 4.1, to lose its capacity to attach to one of tw o classes of high-affinity binding sites on the red cell membrane. The se sites are the ones eliminated by proteolysis in situ of glycophorin C; the surviving type of site is located in a C-terminal peptide of t he glycophorin C, retained on the membrane after proteolysis, which is also the site of attachment of p55. A synthetic peptide, comprising t he 28 C-terminal residues of glycophorin C, also binds protein 4.1. Ph osphorylation of the intact cells, stimulated by phorbol ester, approx imately halves the retention of glycophorin C in the membrane cytoskel etons prepared from these cells and reduces the affinity of extracellu lar glycophorin C epitopes for their antibody. (C) 1995 Academic Press , Inc.