Synthetic collagen-like domain derived from the macrophage scavenger receptor binds acetylated low-density lipoprotein in vitro.

The bovine macrophage scavenger receptor is a 70 kDa membrane protein that is trimerized on the macrophage cell surface. The receptor binds modified low-density lipoproteins (LDL). The core binding site is located within 22 residues at the C-terminus of the collagen-like domain of the receptor. The Lys residue at position 337 plays an important role in ligand binding. Here, the collagen-like domain was constructed using a peptide architecture technique, in which three collagenous peptide chains were crosslinked at their N-termini. The crosslinked peptide showed a collagen-like structure by circular dichroism and existed mainly in a monomeric triple helical form as shown by gel exclusion chromatography. The triple-stranded peptide was demonstrated to bind acetylated LDL (Ac-LDL) using regions derived from Gly323 to Lys340 of the natural bovine scavenger receptor. However, a single-stranded peptide with the same amino acid sequence did not bind Ac-LDL. Furthermore, a triple-stranded mutated peptide in which Lys corresponding to Lys337 in the mother protein was substituted with Ala showed no binding activity to Ac-LDL. These results, taken together, indicate that the synthetic collagen-like peptide has a similar structure to the binding site in the scavenger receptor, and support the view that the collagen-like domain of the natural scavenger receptor recognizes Ac-LDL.