Involved in the modulation of the mitochondrial apoptotic pathway by ensuring the accumulation of cardiolipin (CL) in mitochondrial membranes. The triap1:prelid1 complex probably functions as a phosphatidic acid (PA) transporter across the mitochondrion intermembrane space to provide PA for cardiolipin 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 (By similarity). Required for pronephros development; probably involved at an early stage in the formation of pronephric components derived from the somatic layer (PubMed:18472403). a 1,2-diacyl-sn-glycero-3-phosphate(in) = a 1,2-diacyl-sn-glycero-3-phosphate(out) Monomer. Forms a complex with prelid1 in the mitochondrion intermembrane space. Interacts with prelid3a. Expressed in the developing pronephros. Belongs to the TRIAP1/MDM35 family.