Mitochondrial proton/calcium antiporter that mediates proton-dependent calcium efflux from mitochondrion (By similarity). Crucial for the maintenance of mitochondrial tubular networks and for the assembly of the supercomplexes of the respiratory chain (By similarity). Required for the maintenance of the tubular shape and cristae organization (By similarity). In contrast to SLC8B1/NCLX, does not constitute the major factor for mitochondrial calcium extrusion (By similarity). Inhibited by ruthenium red or its derivative Ru360. Homohexamer (By similarity). Interacts with BCS1L (By similarity). Belongs to the LETM1 family.