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Intrinsically Disordered Protein Threads Through the Bacterial Outer-Membrane Porin OmpF

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Science  28 Jun 2013:
Vol. 340, Issue 6140, pp. 1570-1574
DOI: 10.1126/science.1237864

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Threading Through

Protein antibiotics (bacteriocins) are frequently deployed by Gram-negative bacteria to combat competitors, a trait common in pathogens such as Escherichia coli, Yersinia pestis, Pseudomonas aeruginosa, Xanthomonas campestris, and Klebsiella pneumonia. As a result, bacteriocins are being developed as species-specific antibacterials. Bacteriocins must establish a translocon at the bacterial outer membrane in order to translocate into cells. Working in E. coli, Housden et al. (p. 1570) describe how the deoxyribonuclease, colicin E9, crosses the bacterial cell membrane by threading through a porin.

Abstract

Porins are β-barrel outer-membrane proteins through which small solutes and metabolites diffuse that are also exploited during cell death. We have studied how the bacteriocin colicin E9 (ColE9) assembles a cytotoxic translocon at the surface of Escherichia coli that incorporates the trimeric porin OmpF. Formation of the translocon involved ColE9’s unstructured N-terminal domain threading in opposite directions through two OmpF subunits, capturing its target TolB on the other side of the membrane in a fixed orientation that triggers colicin import. Thus, an intrinsically disordered protein can tunnel through the narrow pores of an oligomeric porin to deliver an epitope signal to the cell to initiate cell death.

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