Involved in the modulation of the mitochondrial apoptotic pathway by ensuring the accumulation of cardiolipin (CL) in mitochondrial membranes. In vitro, the TRIAP1:PRELID1 complex mediates the transfer of phosphatidic acid (PA) between liposomes and probably functions as a PA transporter across the mitochondrion intermembrane space to provide PA for CL synthesis in the inner membrane. Likewise, the TRIAP1:PRELID3A complex mediates the transfer of phosphatidic acid (PA) between liposomes (in vitro) and probably functions as a PA transporter across the mitochondrion intermembrane space (in vivo). Mediates cell survival by inhibiting activation of caspase-9 which prevents induction of apoptosis. a 1,2-diacyl-sn-glycero-3-phosphate(in) = a 1,2-diacyl-sn-glycero-3-phosphate(out) Monomer. Interacts with APAF1 and HSP70. Forms a complex with PRELID1 in the mitochondrion intermembrane space. Interacts with PRELID3A. Belongs to the TRIAP1/MDM35 family.