Diameter of diffusion channel formed by OmpA [outer membrane protein A]

Range ~10 Å
Organism Bacteria Escherichia coli
Reference Arora A, Rinehart D, Szabo G, Tamm LK. Refolded outer membrane protein A of Escherichia coli forms ion channels with two conductance states in planar lipid bilayers. J Biol Chem. 2000 Jan 21 275(3):1594-600. p.1594 right column bottom paragraphPubMed ID10636850
Primary Source [9] Sugawara E, Nikaido H. Pore-forming activity of OmpA protein of Escherichia coli. J Biol Chem. 1992 Feb 5 267(4):2507-11. [10] Sugawara E, Nikaido H. OmpA protein of Escherichia coli outer membrane occurs in open and closed channel forms. J Biol Chem. 1994 Jul 8 269(27):17981-7.PubMed ID1370823, 7517935
Method Osmotic swelling experiments with reconstituted OmpA proteoliposomes
Comments P.1594 right column bottom paragraph:"OmpA has also been reported to form channels or pores in lipid bilayers, although this aspect of the protein is somewhat controversial. Saint et al. (ref 8) measured single channel conductance events in “solvent-free” planar bilayers on the order of 180 pS at 100 mV and in 0.25 m KCl. Based on osmotic swelling experiments with reconstituted OmpA proteoliposomes, Sugawara and Nikaido (primary sources) concluded that OmpA forms a diffusion channel of about 10 Å in diameter. However, only 2–3% of all OmpA molecules were in the open conformation in their preparation, and vesicles containing open channels could be separated from closed channel vesicles by density gradient centrifugation."
Entered by Uri M
ID 112276