Butyrophilin Like Protein 3 (BTNL3)

Butyrophilin is a major immunoglobulin-like protein found in the membrane layer surrounding the milk fat-secreting droplet of mammary epithelial cells. By screening a colon mucosa cDNA library enriched for full-length cDNAs, Shibui et al. (1999) isolated a cDNA encoding BTNL3, which they termed COLF4100. The deduced 433-amino acid transmembrane protein is 42% identical to RO52 (SSA1) and 40% identical to RFP, a DNA-binding protein, with most homology for both in the C terminus.

BTNL3 is 37% identical to BTN1A1. RT-PCR analysis revealed strongest expression of BTNL3 in small intestine, colon, testis, and leukocytes; expression was not detected by Northern blot analysis.