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 memb rane accounting for approx. 5 % of total membrane protein. The major m embrane binding site for P4.2 is contained within the cytoplasmic doma in of band 3 (cdb3), although the precise location of the cdb3 binding site is not known. To identify the cdb3 binding site, we used synthet ic P4.2 peptides (15-mers) that spanned the entire 721-amino-acid larg e isoform of P4.2, and determined the binding of these peptides to cdb 3 in an in vitro binding assay. One peptide, P8 (L(61)FVRRGQPFTIILYF), bound strongly to cdb3 and four others bound less strongly (P22, L(27 1)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 r egion without nearby acidic residues.