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Mitochondrial membrane transport proteins, also known as mitochondrial carrier proteins, are proteins which exist in the membranes of mitochondria. They serve to transport [2] molecules and other factors, such as ions, into or out of the organelles. Mitochondria contain both an inner and outer membrane, separated by the inter-membrane space, or ...
The translocase of the outer membrane (TOM) is a complex of proteins found in the outer mitochondrial membrane of the mitochondria. It allows movement of proteins through this barrier and into the intermembrane space of the mitochondrion. Most of the proteins needed for mitochondrial function are encoded by the nucleus of the cell.
In enzymology, the complex is described as an mitochondrial protein-transporting ATPase (EC 7.4.2.3), or more systematically ATP phosphohydrolase (mitochondrial protein-importing), as the TIM part requires ATP hydrolysis to work. Only 13 proteins necessary for a mitochondrion are actually coded in mitochondrial DNA.
Many MC proteins preferentially catalyze the exchange of one solute for another ().A variety of these 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 and facilitate the transport of inorganic ions, nucleotides, amino acids, keto acids and cofactors across the membrane.
The sorting and assembly machinery is required for the assembly of beta barrel proteins, this includes proteins such as the Tom40 import pore and porin.. Like all mitochondrial proteins, beta barrel proteins are transported into the intermembrane space of mitochondria via the translocase of the outer membrane.
Tim9 and Tim10 make up the group of essential small Tim proteins that assist in transport of hydrophobic precursors across the intermembrane space in mammalian cells. Both Tim9 and Tim10 form a hexamer, the Tim9-Tim10 complex, that when associated, functions as a chaperone to assist translocation of preproteins from the outer mitochondrial membrane to the translocase of the inner membrane.
The carrier preprotein is then inserted into the inner mitochondrial membrane in a potential-dependent fashion. [10] The membrane potential is necessary for both insertion of the precursor into the carrier translocase and lateral release of the protein into the lipid phase of the inner mitochondrial membrane, which completes protein translocation.
ATFS-1 has a nuclear localization sequence that allows it to be imported into the nucleus as well as an N-terminal mitochondrial targeting sequence (MTS) that allows for import into the mitochondria. [12] In healthy cells, ATFS-1 is preferentially targeted to the mitochondrial matrix where it is degraded by the Lon protease.