Key regulator of mitochondrial calcium uniporter (MCU) required for calcium entry into mitochondrion (PubMed:23178883, PubMed:26445506, PubMed:26976564, PubMed:27184846). Plays a direct role in uniporter-mediated calcium uptake via a direct interaction with MCU (PubMed:23178883). Probably involved in the assembly of the membrane components of the uniporter complex (uniplex) (PubMed:27184846). {ECO:0000269|PubMed:23178883, ECO:0000269|PubMed:26445506, ECO:0000269|PubMed:26976564, ECO:0000269|PubMed:27184846}. This is the function of Ensembl gene identifier ENSG00000050393 (MCUR1, mitochondrial calcium uniporter regulator 1).