Mitochondrial carrier

Mitochondrial carriers are proteins from the solute carrier family which transfers molecules across the membranes of the mitochondria.

Function
A variety of substrate carrier proteins, which are involved in energy transfer, have been found in the inner membranes of mitochondria and other eukaryotic organelles such as the peroxisome. Such proteins include: ADP, ATP carrier protein (ADP/ATP translocase); 2-oxoglutarate/malate carrier protein; phosphate carrier protein; tricarboxylate transport protein (or citrate transport protein); Graves disease carrier protein; yeast mitochondrial proteins MRS3 and MRS4; yeast mitochondrial FAD carrier protein; and many others.

Structure
All mitochondrial carriers are encoded by nuclear genes. Most contain a primary structure exhibiting regions of 100 homologous amino acid repeats, the N and C termini face the intermembrane space and there are six definable transmembrane segments in each carrier. All carriers also contain a common sequence, referred to as the MCF motif, in each repeated region, with some variation in one or two signature sequences.

Amongst the members of the mitochondrial carrier family that have been identified, it is the ADP/ATP carrier (AAC) that is responsible for importing ADP into the mitochondria and exporting ATP out of the mitochondria and into the cytosol following synthesis. The AAC is an integral membrane protein that is synthesised lacking a cleavable presequence, but instead contains internal targeting information. It forms a dimer of two identical subunits and consists of a basket shaped structure with six transmembrane helices that are tilted with respect to the membrane, 3 of them kinked at the level of proline residues.

Substrates
Examples of transported compounds include:
 * citrate -
 * ornithine - ,
 * phosphate -, , ,
 * adenine nucleotide -, , ,
 * dicarboxylate -
 * oxoglutarate -
 * glutamate -

Examples
Human proteins containing this domain include:
 * HDMCP, LOC153328, MCART1, MCART2, MCART6, MTCH1, MTCH2
 * UCP1, UCP2, UCP3
 * SLC25A1, SLC25A3, SLC25A4, SLC25A5, SLC25A6, SLC25A10, SLC25A11, SLC25A12, SLC25A13, SLC25A14, SLC25A16, SLC25A17, SLC25A18, SLC25A19, SLC25A21, SLC25A22, SLC25A23, SLC25A24, SLC25A25, SLC25A26, SLC25A27, SLC25A28, SLC25A29, SLC25A30, SLC25A31, SLC25A32, SLC25A33, SLC25A34, SLC25A35, SLC25A36, SLC25A37, SLC25A38, SLC25A39, SLC25A40, SLC25A41, SLC25A42, SLC25A43, SLC25A44, SLC25A45, SLC25A46