MSR1 also known as macrophage scavenger receptor types I and II, belong to the class A macrophage scavenger receptors, which include three different types (1, 2, 3) generated by alternative splicing. These receptors or isoforms are macrophage-specific trimeric integral membrane glycoproteins and have been implicated in many macrophage-associated physiological and pathological processes including atherosclerosis, Alzheimer's disease, and host defense. Recombinant human MSR1, fused to His-tag at N-terminus, was expressed in E.coli.