β-barrel proteins are present in the outer membrane of Gram-negative bacteria and of organel- les of endosymbiotic origin, i.e. mitochondria and chloroplasts where they perform a variety of functions. Mitochondrial β-barrel proteins are important for protein import, metabolite transport and the organelle morphology and distribution. They also seem to play a crucial role in mitochondria evolution. Quite recently a specific pathway for the insertion of β-barrel proteins was identified in both mitochondria and Gram-negative bacteria and was proved to be conserved during evolution.

The primary role in the course of protein import into mitochondria play channels allow translocation of proteins through the mitochondrial membrane and their incorporation into the area of the membranes. In the outer mitochondrial membrane import channel is located TOM complex (translocase of the outer membrane of the) channel and participating in the folding of proteins with complex structure keg b TOB (the topogenesis of mitochondrial outer membrane?-Barrel proteins). In turn, in the intima of the two channels are located on a separate substrate specificity.

Ion channel is the basic solution in the exchange of molecules through the outer mitochondrial membrane. It plays a vital role in the transport of metabolites and protein import. The article discusses the basic properties of the outer membrane channels and their participation in the physiology of mitochondria. The existence of a number of factors governing the functional state of the outer membrane channel indicates that the molecular weight is only one of the factors influencing the passage of molecules through the membrane.