Conserved C-terminal residues within the lectin-like domain of LOX-1 are essential for oxidized low-density-lipoprotein binding

Lectin-like oxidized low-density-lipoprotein (oxLDL) receptor-1 (LOX-I) is a cell-surface endocytosis receptor for atherogenic oxLDL, which is highly expressed in endothelial cells. Recent studies suggest that it may play significant roles in atherogenesis. LOX-I is a type-II membrane protein that structurally belongs to the C-type lectin family molecules. This study was designed to characterize the specific domain on LOX-I that recognizes oxLDL, Truncation of the lectin domain of LOX-1 abrogated oxLDL-binding activity, Deletion of the utmost C-terminal ten amino acid residues (261-270) was enough to disrupt the oxLDL-binding activity. Substitutions of Lys-262 and/or Lys-263 with Ala additively attenuated the activity. Serial-deletion analysis showed that residues up to 265 are required for the expression of minimal binding activity, although deletion of the C-terminal three residues (268-270) still retained full binding activity. Consistently, these alterations in LOX-I impaired the recognition by a functionally blocking monoclonal antibody for LOX-I, These data demonstrated the distinct role of the lectin domain as the functional domain recognizing LOX-1 ligand. The conserved C-terminal residues of lectin-like domain are essential for binding oxLDL. Particularly, the basic amino acid pair is important for the binding.