IDENTIFICATION OF A BAND-3 BINDING-SITE NEAR THE N-TERMINUS OF ERYTHROCYTE-MEMBRANE PROTEIN-4.2

Protein 4.2 (P4.2) is a major component of the erythrocyte plasma membrane accounting for approx. 5 % of total membrane protein. The major membrane binding site for P4.2 is contained within the cytoplasmic domain of band 3 (cdb3), although the precise location of the cdb3 binding site is not known. To identify the cdb3 binding site, we used synthetic P4.2 peptides (15-mers) that spanned the entire 721-amino-acid large isoform of P4.2, and determined the binding of these peptides to cdb3 in an in vitro binding assay. One peptide, P8 (L(61)FVRRGQPFTIILYF), bound strongly to cdb3 and four others bound less strongly (P22, L(271)LNKRRGSVPILRQW; P27, G(346)EGQRGRIWIFQTST; P41, L(556)WRKKLHLTLSANLE; P48, I(661)HRERSYRFRSVWPE). These peptides have in common a cluster of two or three basic amino acid residues (arginine or lysine), in a region without nearby acidic residues.