Essential regulatory subunit of the mitochondrial calcium uniporter complex (uniplex), a complex that mediates calcium uptake into mitochondria (PubMed:24231807, PubMed:26774479, PubMed:27099988). Required to bridge the calcium-sensing proteins MICU1 and MICU2 with the calcium-conducting subunit MCU (PubMed:24231807). Plays a central role in regulating the uniplex complex response to intracellular calcium signaling (PubMed:27099988). Acts by mediating activation of MCU and retention of MICU1 to the MCU pore, in order to ensure tight regulation of the uniplex complex and appropriate responses to intracellular calcium signaling (PubMed:27099988).
