The function of CRLS1 (cardiolipin synthase 1, ENSG00000088766) is as follows. Catalyzes the synthesis of cardiolipin (CL) (diphosphatidylglycerol) by specifically transferring a phosphatidyl group from CDP-diacylglycerol to phosphatidylglycerol (PG) (PubMed:16547353, PubMed:16678169, PubMed:16716149, PubMed:35147173). CL is a key phospholipid in mitochondrial membranes and plays important roles in maintaining the functional integrity and dynamics of mitochondria under both optimal and stress conditions (PubMed:35147173). {ECO:0000269|PubMed:16547353, ECO:0000269|PubMed:16678169, ECO:0000269|PubMed:16716149, ECO:0000269|PubMed:35147173}.