Mitochondrial Porins, Eukaryotic

Abstract

The mitochondrial outer membrane contains a channel that is responsible for the passage of hydrophilic metabolites across the membrane. The channel-forming protein known for many organisms, called mitochondrial porin or VDAC (voltage-dependent anion-selective channel), has a length of about 280 amino acids. The genomes of eukaryotic organisms contain several porin isoforms of not well-defined function. The primary structure of mitochondrial or eukaryotic porins is not particularly hydrophobic and secondary structure predictions suggest that a β-barrel cylinder typical for the secondary structure of bacterial porins also forms the mitochondrial channel. Kinases involved in mitochondrial metabolism such as hexokinase or glycerokinase bind to porin and play an important role in compartment formation in mitochondria. Mitochondrial porins are voltage-gated and switch into ion-permeable substates at voltages higher than 20 to 30 mV. The open channel has a small preference for anion over cations of the same aqueous mobility. The closed states are cation selective and impermeable for ATP and ADP. Mitochondrial porins seem to be involved in apoptosis and the release of cytochrome c. There exists emerging evidence that the cytoplasmic membrane of eukaryotic cells also contains porins of the eukaryotic porin family with a role in cellular metabolism that is not yet understood. Keywords: β-Barrel Cylinder; Mitochondria; Mitochondrial (Eukaryotic Porin); Mitochondrial Inner Membrane; Mitochondrial Outer Membrane; Peripheral Kinases; Porin Family; VDAC