Porins in prokaryotes and eukaryotes: common themes and variations.
Gram-negative bacteria and mitochondria are both covered by two distinct biological membranes. These membrane systems have been maintained during the course of evolution from an early evolutionary precursor. Both outer membranes accommodate channels of the porin family, which are designed for the uptake and exchange of metabolites, including ions and small molecules, such as nucleosides or sugars. In bacteria, the structure of the outer membrane porin protein family of β-barrels is generally characterized by an even number of β-strands; usually 14, 16 or 18 strands are observed forming the bacterial porin barrel wall. In contrast, the recent structures of the mitochondrial porin, also known as VDAC (voltage-dependent anion channel), show an uneven number of 19 β-strands, but a similar molecular architecture. Despite the lack of a clear evolutionary link between these protein families, their common principles and differences in assembly, architecture and function are summarized in the present review.
Zeth
Kornelius
K
Max Planck Institute of Developmental Biology, Department Protein Evolution, Spemannstr. 35, D-72076 Tübingen, Germany. kornelius.zeth@tuebingen.mpg.de
Thein
Marcus
M
D001426:Bacterial Proteins / Q000737:chemistry* / Q000378:metabolism; D056890:Eukaryota / Q000378:metabolism; D008928:Mitochondria / Q000378:metabolism; D008954:Models, Biological; D018272:Porins / Q000737:chemistry* / Q000378:metabolism; D011487:Protein Conformation; D050995:Voltage-Dependent Anion Channel 1 / Q000737:chemistry / Q000378:metabolism; D050994:Voltage-Dependent Anion Channels / Q000737:chemistry* / Q000378:metabolism
D001426:Bacterial Proteins; D018272:Porins; D050994:Voltage-Dependent Anion Channels; D050995:Voltage-Dependent Anion Channel 1