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 (PubMed:23931759). 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) (PubMed:26071602). Mediates cell survival by inhibiting activation of caspase-9 which prevents induction of apoptosis (PubMed:15735003). {ECO:0000269|PubMed:15735003, ECO:0000269|PubMed:23931759, ECO:0000269|PubMed:26071602}. This is the function of Ensembl gene identifier ENSG00000170855 (TRIAP1, TP53 regulated inhibitor of apoptosis 1).