Mapping a heparin binding site on ErbB-3 epidermal growth factor receptor

Signaling via the ErbB-family of receptors plays an important role in mamma lian development and oncogenesis. Here we show that the ErbB-3 receptor, bu t not other members of this receptor family, binds to immobilized heparin a nd can be dissociated only at a high ionic strength comparable to that requ ired for fibroblast growth factor receptors. Competition-binding analysis s uggests that this interaction is specific and requires highly sulfated spec ies of heparan sulfate. Primary sequence analysis of ErbB-3 identified a ba sic amino acid cluster (KHNRPRR472)-K-466 localized to the proximal, cystei ne-rich extracellular ligand binding domain of the receptor, with charge de nsity and distribution compatible with, but different to, known linear hepa rin binding motifs. Site-directed mutagenesis, replacing this sequence with the corresponding residues from ErbB-1, resulted in complete loss of hepar in binding activity of the chimeric receptor. Finally, antibodies directed to the putative heparin binding peptide, efficiently bind the native recept or suggesting a novel target for blocking heparin mediated ErbB-3 interacti ons. (C) 2001 Academic Press.