Class A scavenger receptors contain an intracellular domain, a transmembrane region, a coiled-coil domain, a collagenous domain, and the SR cysteine-rich domain (reviewed in Areschoug and Gordon 2009, Bowdish and Gordon 2009). The coiled coil domains interact to form trimers. The collagenous domain (Rohrer et al. 1990, Acton et al. 1993) and/or the SR cysteine-rich domain (Brannstrom et al. 2002) bind ligands and determine the specificity of the receptor.