The function of complexes between the outer mitochondrial membrane pore (VDAC) and the adenine nucleotide translocase in regulation of energy metabolism and apoptosis.
The outer mitochondrial membrane pore (VDAC) changes its structure either voltage-dependently in artificial membranes or physiologically by interaction with the adenine nucleotide translocase (ANT) in the c-conformation. This interaction creates contact sites and leads in addition to a specific organisation of cytochrome c in the VDAC-ANT complexes. The VDAC structure that is specific for contact sites generates a signal at the surface for several proteins in the cytosol to bind with high capacity, such as hexokinase, glycerol kinase and Bax. If the VDAC binding site is not occupied by hexokinase, the VDAC-ANT complex has two critical qualities: firstly, Bax gets access to cytochrome c and secondly the ANT is set in its c-conformation that easily changes conformation into an unspecific channel (uniporter) causing permeability transition. Activity of bound hexokinase protects against both, it hinders Bax binding and employs the ANT as anti-porter. The octamer of mitochondrial creatine kinase binds to VDAC from the inner surface of the outer membrane. This firstly restrains interaction between VDAC and ANT and secondly changes the VDAC structure into low affinity for hexokinase and Bax. Cytochrome c in the creatine kinase complex will be differently organised, not accessible to Bax and the ANT is run as anti-porter by the active creatine kinase octamer. However, when, for example, free radicals cause dissociation of the octamer, VDAC interacts with the ANT with the same results as described above: Bax-dependent cytochrome c release and risk of permeability transition pore opening.
Vyssokikh
Mikhail Y
MY
A.N. Belozersky Institute of Physico-Chemical Biology, Moscow State University, Moscow, Russia.
Brdiczka
Dieter
D
D000818:Animals; D017209:Apoptosis / Q000502:physiology*; D001665:Binding Sites; D002463:Cell Membrane Permeability; D003402:Creatine Kinase / Q000737:chemistry / Q000378:metabolism; D045304:Cytochromes c / Q000737:chemistry / Q000378:metabolism; D004734:Energy Metabolism / Q000502:physiology*; D005991:Glycerol Kinase / Q000378:metabolism; D006593:Hexokinase / Q000378:metabolism; D006801:Humans; D007425:Intracellular Membranes / Q000737:chemistry / Q000378:metabolism; D008928:Mitochondria / Q000737:chemistry / Q000378:metabolism* / Q000648:ultrastructure; D000226:Mitochondrial ADP, ATP Translocases / Q000737:chemistry / Q000378:metabolism*; D008958:Models, Molecular; D018272:Porins / Q000737:chemistry / Q000378:metabolism*; D011487:Protein Conformation; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D019253:Proto-Oncogene Proteins c-bcl-2; D050994:Voltage-Dependent Anion Channels; D051028:bcl-2-Associated X Protein
C494826:BAX protein, human; D018272:Porins; D011518:Proto-Oncogene Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D050994:Voltage-Dependent Anion Channels; D051028:bcl-2-Associated X Protein; D045304:Cytochromes c; D000226:Mitochondrial ADP, ATP Translocases; D006593:Hexokinase; D005991:Glycerol Kinase; D003402:Creatine Kinase