The protein domain architecture of the class A scavenger receptors. Structures are scaled based on the length of each domain. The cytoplasmic and transmembrane domains were determined using TMHMM software; α-helical domains were determined using the JUFO Server and PSIPRED. The boundaries of the collagenous, SRCR, and C-type lectin domains were determined using NCBI’s CDD. Heptad coiled-coil motifs of the α-helical domains were identified based on the definition put forth in [3, 4]. Domain boundaries are supported by Additional file 1: Table S2.