Binding of a high reactive heparin to human apolipoprotein E: identification of two heparin-binding domains

Ligand-blotting and dot-blotting procedures were used to investigate the binding of [125I]-heparin to apolipoprotein E, its thrombin fragments E22 (residues 1-191) and E12 (residues 192-299), and to nine apolipoprotein E synthetic fragments. E22 and E12 bound [125I] heparin indicating multiple heparin-binding domains. Synthetic peptides of apoE corresponding to residues 129-169, 139-169, and 144-169, but not 148-169, bound [125I] heparin suggesting that residues 144-147 (Leu-Arg-Lys-Arg) in E22 are important for binding. Peptide 202-243 and 211-243 but not 219-243 bound [125I] heparin suggesting that residues 211-218 (Gly-Glu-Arg-Leu-Arg-Ala-Arg-Met) comprise a portion of the E12 heparin-binding domain.