Key regulator of mitochondrial calcium uniporter (MCU) required for calcium entry into mitochondrion (PubMed:23178883, PubMed:26445506, PubMed:27184846, PubMed:26976564). 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). Interacts (via coiled coil regions) with MCU; the interaction is direct (PubMed:23178883, PubMed:26341627, PubMed:27184846, PubMed:26976564). Interacts with SMDT1/EMRE; the interaction is direct (PubMed:27184846). Interacts with PPIF (PubMed:26976564). Ubiquitously expressed. Belongs to the CCDC90 family. A paper reported that MCUR1 has an indirect role as a regulator of mitochondrial calcium uniporter (MCU) and is involved in cytochrome c oxidase (COX) assembly instead (PubMed:25565209). Subsequent publications however confirmed the function of MCUR1 as a regulator of MCU (PubMed:26445506, PubMed:27184846).