22 is responsible for allowing other mitochondrial transporters to insert themselves into the inner membrane, whereas TIM23 reads proteins with an N-terminus precursor for import into the membrane or matrix. ADP, ATP translocase ADP, ATP translocase is responsible for regulating the movement of ADP and ATP in and out of the inner membrane. ATP is sorted into the cytosol, while ADP is sorted into the mitochondrial matrix to undergo oxidative phosphorylation. Due to the constant demand of ATP production, ADP, ATP translocases are in higher abundance than other transporters. ADP, ATP translocase is a small protein, ~30-33 kDa, composed of 6 transmembrane α-helices, that form 3 repeat domains for an overall funnel-like structure in the membrane. Towards the center of the funnel structure it has a 7 amino acid loop 12. It is structurally unique when compared to other proteins that interact with ATP in that it lacks adenosine monophosphate and requires at least two phosphate groups to allow for passage of the molecule. It's composed of 297 amino acid residues, with 18 of them being charged molecules. The ADP, ATP translocase is opened in the presence of Ca2+. Phosphate transport proteins Phosphate transport proteins are similar in structure and are both part of the same family of mitochondrial carriers. It consists of 6 transmembrane α-helices, but lacks the 7 amino acid loop 12 found in ADP, ATP translocase. Phosphate transport proteins are responsible for transport of phosphate across the inner membrane so it can be used in the phosphorylation of ADP. Mutations of mitochondrial membrane transporters Mutations of DNA coding for mitochondrial membrane transport proteins are linked to a wide range of diseases and disorders, such as cardiomyopathy, encephalopathy, muscular dystrophy, epilepsy, neuropathy, and fingernail dysplasia. Most mutations of mitochondrial membrane transporters are autosomal recessive. Mutations to transporters within the inner mitochondrial membrane mostly affect high-energy tissues due to the disruption of oxidative phosphorylation. For example, decreased mitochondrial function has been linked to heart failure and hypertrophy. This mitochondrial response translates into a shift towards glycolysis and lactate production that can cause tumor formation and proliferation of the tissues. Examples Examples of mitochondrial transport proteins include the following: The mitochondrial permeability transition pore, which opens in response to increased mitochondrial calcium (Ca2+) load and oxidative stress The mitochondrial calcium uniporter which transports calcium from the cytosol of the cell into the mitochondrial matrix The mitochondrial sodium/calcium exchanger, which carries