The enzymes are predominantly in the matrix, requiring that substrates be transported across the mitochondrial inner membrane. The transport is catalysed by a superfamily of proteins, which show strong sequence homology across the whole spectrum of the eukaryote world, but no obvious prokaryote precursor. Transport of metabolites will be covered in greater detail later. Ion transport catalysed by ionophores . Characterization of the mechanisms of ionophores played a crucial role in our understanding of the proton gradient, and its role in chemiosmotic coupling.
Transport is by a carrier mechanism.
As a consequence, the electrochemical potential for the transported species is equal across the membrane, and the equilibrium condition applies. The mechanism of valinomycin will be discussed further in the context of transport. Nigericin catalyses the neutral exchange of monovalent cations across biological membranes, with a broad specificity. The mechanism of nigericin is discussed in greater detail here. The gramicidin pore is much studied, and will be discussed in greater detail later in the context of transport.