Mitochondrial membrane transport proteins are proteins which exist in the membranes of mitochondria and which serve to transport molecules and other factors such as ions into or out of the organelles.
The mitochondrial sodium/calcium exchanger, which carries Ca2+ ions out of the matrix in exchange for Na+ ions. These transport proteins serve to maintain the proper electrical and chemical gradients in mitochondria by keeping ions and other factors in the right balance between the inside and outside of mitochondria.