BCL2L15 is a 163 amino acid protein and novel member of the Bcl-2 family that contains both BH2 and BH3 regions, but not BH1, BH4 or a C-terminal hydrophobic membrane anchor. Like Bcl-GL, Bfk does not bind to any Bcl-2 family members, even though its BH3 motif can mediate association with prosurvival proteins. Bfk localizes to cytoplasm, but unlike Bcl-GL, Bfk does not associate with organelles. Existing as four alternatively spliced isoforms, the pro-apoptotic isoforms of Bfk may help to protect against the development of human gastrointestinal malignancy. Bfk is found at low levels in stomach, ovary, bone marrow and spleen, but Bfk is highly expressed in mammary gland during pregnancy, suggesting that Bfk may play a role in mammary development. Bfk appears to be a cytosolic protein whose gene maps to chromosome 1p13.2. Chromosome 1 is the largest human chromosome spanning about 260 million base pairs and making up 8% of the human genome.