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PMID:1370823

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Citation

Sugawara, E and Nikaido, H (1992) Pore-forming activity of OmpA protein of Escherichia coli. J. Biol. Chem. 267:2507-11

Abstract

Escherichia coli outer membrane protein OmpA was purified to homogeneity, as a monomer, from a K12 derivative deficient in both OmpF and OmpC porins. When proteoliposomes reconstituted from the purified OmpA, phospholipids, and lithium dodecyl sulfate were tested for permeability to small molecules by osmotic swelling, it was found that OmpA produced apparently nonspecific diffusion channels that allowed the penetration of various solutes. The pore-forming activity was destroyed by the heat denaturation of the OmpA protein, and the use of an OmpA-deficient mutant showed that the activity was not caused by copurifying contaminants. The size of the OmpA channel, estimated by comparison of diffusion rates of solutes of different sizes, was rather similar to that of E. coli OmpF and OmpC porins, i.e. about 1 nm in diameter. The rate of penetration of L-arabinose caused by a given amount of OmpA protein, however, was about a hundredfold lower than the rate produced by the same amount of E. coli OmpF porin. The addition of large amounts of lithium dodecyl sulfate to the reconstitution mixture increased the permeability through the OmpA channel, apparently by facilitating the correct insertion of OmpA into the bilayer.

Links

PubMed

Keywords

Arabinose/metabolism; Bacterial Outer Membrane Proteins/isolation & purification; Bacterial Outer Membrane Proteins/pharmacology; Biological Transport; Cell Membrane/metabolism; Diffusion; Electrophoresis, Polyacrylamide Gel; Escherichia coli/metabolism; Ion Channels; Phospholipids/metabolism; Protein Denaturation; Proteolipids; Sodium Dodecyl Sulfate/metabolism

Significance

Annotations

Gene product Qualifier GO Term Evidence Code with/from Aspect Extension Notes Status

ECOLI:OMPA

part_of

GO:0046930: pore complex

ECO:0000314: direct assay evidence used in manual assertion

C

Seeded From UniProt

complete

ECOLI:OMPA

enables

GO:0015288: porin activity

ECO:0000314: direct assay evidence used in manual assertion

F

Seeded From UniProt

complete

ECOLX:E0WA88

GO:0009279: cell outer membrane

ECO:0000315:

C

Furthermore, the experiment using the OmpA-deficient mutant HN742 (Fig. 6) showed conclusively that the channel formation was caused by OmpA, denaturation of OmpA essentially abolished the solute diffusion process and that nonporin proteins such as bovine serum albumin could not facilitate the solute diffusion across the membrane.

complete
CACAO 4099


See also

References

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