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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). While porins all share a common fold, the detailed makeup and the shape of the inside of the barrel (the channel) determines which molecules pass through the porin and which are retained.



The function on a porin depends on the size and lining of the channel.

Maltoporin (LamB) facilitates the diffusion of maltodextrin across the membrane[1].

Chitoporin (Chitp) facilitates the diffusion of chitooligosaccharides across the outer membrane of some bacteria[2].

Voltage-Dependent Anion Channel (VDAC) are ion channel Omps found in outer mitochondrial membrane[3]. In Pseudomonas aeruginosa the porin gene products are named OprD, OprE, OprK, OprP, etc. and OpdC, OpdH, etc.

For discussion of specific porins, see


E. coli OmpC is a trimeric transmembrane protein with a porin fold (PDB code 2j1n)

Drag the structure with the mouse to rotate


The scene showing channels as pseudoatoms is from a page (User:Eric_Martz/Sandbox_19) made by Eric Martz. Eric also helped creating the surface rendition of the channels (technical details here: Image:Tunnels.jvxl).


  1. 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
  2. Suginta W, Chumjan W, Mahendran KR, Schulte A, Winterhalter M. Chitoporin from Vibrio harveyi, a channel with exceptional sugar specificity. J Biol Chem. 2013 Apr 19;288(16):11038-46. PMID:23447539 doi:10.1074/jbc.M113.454108
  3. 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
  4. 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
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