Activator of apoptosis harakiri is a protein in humans that is encoded by HRK gene. Activator of apoptosis Hrk regulates apoptosis through interaction with death-repressor proteins Bcl-2 and Bcl-X(L). The HRK protein lacks significant homology to other BCL2 family members except for an 8-amino acid region that was similar to the BCL2 homology domain-3 (BH3) motif of BIK. HRK interacts with BCL2 and BCLXL via the BH3 domain, but not with the death-promoting BCL2-related proteins BAX, BAK, or BCLXS. HRK localizes to membranes of intracellular organelles in a pattern similar to that previously reported for BCL2 and BCLXL.