The 'ins' and 'outs' of mitochondrial membrane channels.
The outer membrane of the mitochondrion contains thousands of copies of a pore-forming protein called VDAC or porin. Considerable progress has been made towards elucidating the molecular structure of this channel. Moreover, mounting evidence that the permeability of VDAC may be regulated is challenging the textbook notion of the outer membrane as a simple sieve. Numerous other channel activities have been detected by electrophysiol approaches in both the outer and inner mitochondrial membranes. The inner-membrane channels do not appear to be open under normal physiological conditions and so should not dissipate energy-transducing ion gradients. The biological functions of the different classes of mitochondrial channels are uncertain, but several possibilities (including protein translocation) are being explored.
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Wadsworth Center for Laboratories and Research, New York State Department of Health, Albany 12201-0509.
D001425:Bacterial Outer Membrane Proteins / Q000378:metabolism / Q000648:ultrastructure; D002463:Cell Membrane Permeability / Q000502:physiology; D006801:Humans; D007473:Ion Channels / Q000502:physiology*; D008564:Membrane Potentials / Q000502:physiology; D008928:Mitochondria / Q000502:physiology*; D009492:Neurospora crassa / Q000648:ultrastructure; D018272:Porins
D001425:Bacterial Outer Membrane Proteins; D007473:Ion Channels; D018272:Porins