Mitochondrial membrane transport protein

[5][6] The TOM complex, part of the TOM/TIM supercomplex, is essential for the translocase of almost all mitochondrial proteins which consists of at least 7 different subunits.

Tom40 has a large pore diameter of 22Å that can allow the accommodation of partially folded protein structure[19] The inner wall of Tom40 has a charged region that allows interaction with hydrophilic precursor proteins while the hydrophobic precursor of ADP/ATP carrier can be crosslinked with the hydrophobic region of Tom40.

[20] The SAM Complex is essential for sorting and assembling beta-barrel proteins from the intermembrane space side into the outer membrane.

[22][25][26] Sam50 belongs to the conserved Omp85 protein family which can be characterized by a 16-stranded β-barrel and by a different number of polypeptide transport-associated (POTRA) domains.

VDAC plays a crucial role in facilitating energy metabolism by transporting ADP and ATP in and out of the outer membrane.

VDAC operation is voltage-dependent in which it closes at high voltage and can partially open towards slightly reduced anion selectivity.

Both subunits are necessary for stabilizing partner proteins and for outer membrane protein biogenesis[38] The inner mitochondrial membrane is a structure that surrounds the mitochondrial matrix, characterized by many folds and compartments that form crista and is the site of oxidative phosphorylation and ATP synthesis.

[3][39] The high concentration of cardiolipin, a type of lipid and about 20% of the inner membrane composition, makes it impermeable to most molecules.

Specialized transporters arranged in specific configurations are required to regulate the diffusion of molecules across the membrane.

Cytochrome c is and electron carrier protein that travels between complex III and IV, and triggers apoptosis if it leaves the cristae.

[42][43] 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.

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 consists of 6 transmembrane α-helices, but lacks the 7 amino acid loop 12 found in ADP, ATP translocase.

[39] 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.

Mutations to transporters within the inner mitochondrial membrane mostly affect high-energy tissues due to the disruption of oxidative phosphorylation.

This mitochondrial response translates into a shift towards glycolysis and lactate production that can cause tumor formation and proliferation of the tissues.