Function
Porin or Outer Membrane Proteins (Omps) act as channels which allow passive diffusion of sugars, ions and amino acids. They are beta barrel proteins which traverse the cell membrane. In E. coli they are named according to their genes: C, F, G, etc. (OmpC, OmpF, OmpG).
Voltage-Dependent Anion Channel (VDAC) are ion channel Omps found in outer mitochondrial membrane[1]. In Pseudomonas aeruginosa the porin gene products are named OprD, OprE, OprK, OprP, etc. and OpdC, OpdH, etc.
Maltoporin (LamB) facilitates the diffusion of maltodextrin across the membrane[2].
See more details in
Structure
One representative porin structure is the crystal structure osmoporin OmpC from Escherichia coli (2j1n). OmpC has three beta-barrels associated to form a tight trimer [3]. Porin is a transmembrane protein, as can be seen from the around the protein, this makes it possible to submerge in the lipid bilayer (hydrophobic amino acids are sandybrown, hydrophilic ones are cyan). As you can see the hole in the protein is made of mainly hydrophilic chains thus making it possible for the sugar to pass through (these scenes were created by Nádori Gergely).
3D structures of Porin
Porin 3D structures
- ↑ Shoshan-Barmatz V, Israelson A, Brdiczka D, Sheu SS. The voltage-dependent anion channel (VDAC): function in intracellular signalling, cell life and cell death. Curr Pharm Des. 2006;12(18):2249-70. PMID:16787253
- ↑ Van Gelder P, Dumas F, Bartoldus I, Saint N, Prilipov A, Winterhalter M, Wang Y, Philippsen A, Rosenbusch JP, Schirmer T. Sugar transport through maltoporin of Escherichia coli: role of the greasy slide. J Bacteriol. 2002 Jun;184(11):2994-9. PMID:12003940
- ↑ Basle A, Rummel G, Storici P, Rosenbusch JP, Schirmer T. Crystal structure of osmoporin OmpC from E. coli at 2.0 A. J Mol Biol. 2006 Oct 6;362(5):933-42. Epub 2006 Aug 3. PMID:16949612 doi:10.1016/j.jmb.2006.08.002