butyrophilin subfamily member A1 and A2 (BTN1A and BTN2A)
This domain, consisting of the distinct N-terminal PRY subdomain followed by the SPRY subdomain, is found at the C-terminus of butyrophilin family 1A and 2A (BTN1A and BTN2A). BTNs belong to receptor glycoproteins of immunoglobulin (Ig) superfamily, characterized by the presence of extracellular Ig-like domains (IgV and/or IgC). BTN1A plays a role in the secretion, formation and stabilization of milk fat globules. The B30.2 domain of BTN1A1 binds the enzyme xanthine oxidoreductase (XOR) in order to participate in milk fat globule secretion; this interaction may lead to the production of reactive oxygen species, which have immunomodulatory and antimicrobial functions. Duplication events have led to three paralogs of BTN2A in primates: BTN2A1, BTN2A2, and BTN2A3. In humans, only BTN2A1 has been functionally characterized; it has been detected on epithelial cells and leukocytes, and identified as a novel ligand of dendritic cell-specific ICAM-3 grabbing nonintegrin (DCSIGN), a C-type lectin receptor that acts as an internalization receptor for HIV-1, HCV, and other pathogens. BTN2A2 mRNA has been shown to be expressed in circulating human immune cells.
Jiyao W et al.(2023). "The conserved domain database in 2023.",