Mitochondrial proton/calcium antiporter that mediates proton-dependent calcium efflux from mitochondrion (PubMed:19797662). Crucial for the maintenance of mitochondrial tubular networks and for the assembly of the supercomplexes of the respiratory chain (PubMed:18628306). Required for the maintenance of the tubular shape and cristae organization (PubMed:18628306). In contrast to SLC8B1/NCLX, does not constitute the major factor for mitochondrial calcium extrusion (PubMed:24898248). Inhibited by ruthenium red or its derivative Ru360. Homohexamer (By similarity). Can form 2 complexes: a major (300 kDa) and a minor complex (500-600 kDa) (PubMed:18628306). Interacts with BCS1L (PubMed:18628306). May be due to intron retention. May be due to intron retention. Belongs to the LETM1 family. Incomplete prediction of CDS at the C-terminus.