Butyrophilin is the major protein associated with fat droplets in the milk. This gene is a member of the BTN2 subfamily of genes, which encode proteins belonging to the butyrophilin protein family. The gene is located in a cluster on chromosome 6, consisting of seven genes belonging to the expanding B7/butyrophilin-like group, a subset of the immunoglobulin gene superfamily. The encoded protein is a type 1 receptor glycoprotein involved in lipid, fatty-acid and sterol metabolism. Several alternatively spliced transcript variants of this gene have been described, but the full-length nature of some variants has not been determined.
Rhodes DA, Stammers M, Malcherek G, Beck S, Trowsdale J (February 2001). "The cluster of BTN genes in the extended major histocompatibility complex". Genomics. 71 (3): 351–62. doi:10.1006/geno.2000.6406. PMID11170752.