Evolutionary diversity of the mitochondrial calcium uniporter

Abstract

Calcium uptake into mitochondria occurs via a recently identified ion channel called the uniporter. Here, we characterize the phylogenomic distribution of the uniporter's membrane-spanning pore subunit (MCU) and regulatory partner (MICU1). Homologs of both components tend to co-occur in all major branches of eukaryotic life, but both have been lost along certain protozoan and fungal lineages. Several bacterial genomes also contain putative MCU homologs that may represent prokaryotic calcium channels. The analyses indicate that the uniporter may have been an early feature of mitochondria.

Fig. 1

(A) Distribution of MCU (black) and MICU1 (red) homologs across 138 eukaryotes; a detailed version is available in fig. S1. (B) Protein domain architecture of selected MCU homologs, including mitochondrial targeting sequence (MTS, white rectangle), coiled-coil domain (coil), transmembrane domain (TM, shaded rectangle), and the “DIME” motif. L, Leu; T, Thr; P, Pro; V, Val; W, Trp. (C) Genomic organization of MICU1 and MCU across vertebrate genomes.