Porins

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Porins
Porins
Schematic representation of a sucrose- specific porin from Salmonella : side view (parallel to the membrane) of the β-barrel structure with the anti-parallel β-pleated sheets in the ribbon model for the monomer.
Mass / length primary structure 300-420 amino acids
Transporter classification
TCDB 1.B
designation Β barrel porins
Occurrence
Parent taxon Mitochondria, plastids, bacteria
Exceptions some gram-positive bacteria

Surface model of the same protein as a biologically active homotrimer.

Porins are pore-forming , unspecific transmembrane proteins in the outer membrane of gram-negative bacteria , chloroplasts and mitochondria . They are used for the exchange of substances through the membrane.

They were discovered and named by Hiroshi Nikaidō .

The construction principle of all porins is the same: They consist of a chain of 300-420 amino acids that is folded into a 16- or 18-stranded anti-parallel β-barrel (one strand corresponds to a β-sheet ). The wall of the pore is very thin; it is only as strong as an amino acid. Inside the porin there is a constriction with some ionizable amino acids, at which the permeability of the pore is determined.

If one examines the porins of different types, one finds that they are similar in a number of structural features. This indicates homology and can be used as evidence that the porins are very conservative proteins that have changed little in the course of evolution .

Mitochondrial porin (Ø ~ 4 nm) lies in the outer mitochondrial membrane and enables the free diffusion of molecules up to about 5000 Da . It is also known as VDAC (voltage-dependent anion channel), as it allows the controlled passage of anionic molecules such as chloride , phosphate or nucleotides .

Individual evidence

  1. ↑ Forst, D. et al. (1998): Structure of the sucrose-specific porin ScrY from Salmonella typhimurium and its complex with sucrose. In: Nat. Struct. Biol. Vol. 5, pp. 37-46. PMID 9437428 PDB  1A0S
  2. ^ Phillip E. Klebba: The porinologist . In: Journal of Bacteriology . Vol. 187, No. December 24 , 2005, pp. 8232-8236 , doi : 10.1128 / JB.187.24.8232-8236.2005 , PMID 16321927 .
  3. ↑ Vander Heiden MG, Li XX, Gottleib E, Hill RB, Thompson CB, Colombini M: Bcl-xL promotes the open configuration of the voltage-dependent anion channel and metabolite passage through the outer mitochondrial membrane . In: J. Biol. Chem. . 276, No. 22, June 2001, pp. 19414-9. doi : 10.1074 / jbc.M101590200 . PMID 11259441 .

literature

  • Hiroshi Nikaido (2003): Molecular Basis of Bacterial Outer Membrane Permeability Revisited. In: Microbiol. Mol. Biol. Rev. Vol. 67, pp. 593-656. PMID 14665678