PRY/SPRY domain of butyrophilin 3 (BTN3), includes BTN3A1, BTN3A2, BTN3A3 as well as BTN-like 3 (BTNL3); BTN3A also known as CD277
This domain, consisting of the distinct N-terminal PRY subdomain followed by the SPRY subdomain, is found at the C-terminus of butyrophilin family 3A (BTN3A); duplication events have led to three paralogs in primates: BTN3A1, BTN3A2, and BTN3A3. BTNs belong to receptor glycoproteins of immunoglobulin (Ig) superfamily, characterized by the presence of extracellular Ig-like domains (IgV and/or IgC). BTN3 transcripts are ubiquitously present in all immune cells (T cells, B cells, NK cells, monocytes, dendritic cells, and hematopoietic precursors) with different expression levels; BTN3A1 and BTN3A2 are expressed mainly by CD4+ and CD8+ T cells, BTN3A2 is the major form expressed in NK cells, and BTN3A3 is poorly expressed in these immune cells. The PRY/SPRY domain of the BTN3A1 isoform mediates phosphoantigen (pAg)-induced activation by binding directly to the pAg.
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