Macrophage scavenger receptors (MSR) mediate the binding, internalization and processing of the wide range of negatively charged macromolecules. Functional receptors are trimers of two C-terminally different subunit containing 6 functional domains; cytoplasmic, transmembrane, spacer, alpha-helical coiled-coil, collagen-like, type specific domain. The C-terminal region of the collagen-like domain is essential for the ligand recognition of MSR. Human MSR gene consists of 11 exons, and two types of mRNAs are generated by alternative splicing from exon 8 to either exon 9 (type II) or to exons 10 and 11 (type I). Exon 1 encodes the 5' untranslated resion followed by a 12 kb intron which separates the transcription initiation site and the translation initiation site. Exon 2 encodes a cytoplasmic domain; Exon 3, a transmembrane domain; Exons 4 and 5, an alpha-helical coiled-coil; and exon 6 to 8, a collagen-like domain. The MSR gene consists of a mosaic of exons which encode the functional domains. The arrangement of exons helped determine the fine structural characteristics of functional domains.