Purification of the mitochondrial calcium uniporter from beef heart and characterization of its properties

A low-molecular-weight component (LMC) inducing selective transport of calcium across the bilayer lipid membrane has been isolated from mitochondria of bovine heart by the method developed in our laboratory, which excludes the use of detergents and proteolytic enzymes. It is shown that, in the presence of 10 mM CaCl₂, LMC forms conduction channels in the membrane in multiples of 5 pS. The specific inhibitor of the mitochondrial calcium uniporter, ruthenium red, closes Ca²⁺-induced channels formed in the membrane by LMC. In the absence of calcium or in the presence of potassium ions only, the component is incapable of forming channels of conduction. It is shown using nuclear magnetic resonance that LMC is a complex consisting of lipids, amino acids, and sugars with a molecular weight of 1–2 kDa.