Escherichia coli outer membrane transport protein

While gramicidin and other channel formers can show high transport rates, they do not show the high selectivity that characterizes natural channels. There is much interest at present in a class of proteins called porins, which form natural pores in the outer membranes of Gram-negative bacteria. Several different porin proteins have been isolated from Escherichia coli. These form water-filled channels of various sizes in membranes. Thus the proteins OmpC and OmpF seem to be cation-specific channels while other proteins give larger diameter channels that seem to be specific for anions.34,35... 

Ruiz, N., Cronenberg, L.S., Kahne, D., Silhavy, TJ. Identification of two inner-membrane proteins required for the transport of lipopolysaccharide to the outer membrane of Escherichia coli. Proc Natl Acad Sci USA 105 (2008) 5537-5542. 

Sperandeo, P., Lau, F.K., Carpentieri, A., De Castro, C., Molinaro, A., Deho, G., Silhavy, T.J., Polissi, A. Functional analysis of the protein machinery required for transport of lipopolysac-charide to the outer membrane of Escherichia coli. J Bacteriol 190 (2008) 4460 1469. 

The Gram-negative bacterium Escherichia coli is a versatile host and can be used both as a whole cell for biosensor purpose, if the sensing protein is made accessible to the pollutant by exposure on the bacterium surface, and as a factory to yield amounts of protein biomediator to be purified and assembled in a biosensor. The overetqtressed proteins in E. coli, depending on their target signals, can be transported to the outer cell and secreted in the cultivation medium or localised in distinct cell compartments. We intend as the outer cell of E. coli the extracellular space and the cell envelope, which consists of the outer membrane, the periplasm space and the cytoplasmic membrane. 

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