Charged collagen structure mediates the recognition of negatively charged macromolecules by macrophage scavenger receptors.

Macrophage scavenger receptors mediate the recognition of a wide range of negatively charged macromolecules including modified low density lipoproteins (LDL). Truncated bovine receptors lacking residues 330-342, which include the conserved lysine cluster of a collagen-like domain, were unable to degrade modified LDL in spite of their expression on the cell surface. Substitution of lysine 337 into alanine abolished the acetyl-LDL degradation and binding at 37 degrees C, but did not abolish the 4 degrees C binding. In contrast, substitution of more than 2 lysines in this region are needed to abolish the oxidized LDL degradation and 37 degrees C binding. Based on computational modeling of this domain, we propose that a "charged collagen" structure containing a lysine cluster forms a positively charged groove which specifically interacts with negatively charged ligands.