Colicin occlusion of OmpF and TolC channels: outer membrane translocons for colicin import.
Biophys J
; 87(6): 3901-11, 2004 Dec.
Article
em En
| MEDLINE
| ID: mdl-15465872
ABSTRACT
The interaction of colicins with target cells is a paradigm for protein import. To enter cells, bactericidal colicins parasitize Escherichia coli outer membrane receptors whose physiological purpose is the import of essential metabolites. Colicins E1 and E3 initially bind to the BtuB receptor, whose beta-barrel pore is occluded by an N-terminal globular "plug". The x-ray structure of a complex of BtuB with the coiled-coil BtuB-binding domain of colicin E3 did not reveal displacement of the BtuB plug that would allow passage of the colicin (Kurisu, G., S. D. Zakharov, M. V. Zhalnina, S. Bano, V. Y. Eroukova, T. I. Rokitskaya, Y. N. Antonenko, M. C. Wiener, and W. A. Cramer. 2003. Nat. Struct. Biol. 10948-954). This correlates with the inability of BtuB to form ion channels in planar bilayers, shown in this work, suggesting that an additional outer membrane protein(s) is required for colicin import across the outer membrane. The identity and interaction properties of this OMP were analyzed in planar bilayer experiments.OmpF and TolC channels in planar bilayers were occluded by colicins E3 and E1, respectively, from the trans-side of the membrane. Occlusion was dependent upon a cis-negative transmembrane potential. A positive potential reversibly opened OmpF and TolC channels. Colicin N, which uses only OmpF for entry, occludes OmpF in planar bilayers with the same orientation constraints as colicins E1 and E3. The OmpF recognition sites of colicins E3 and N, and the TolC recognition site of colicin E1, were found to reside in the N-terminal translocation domains. These data are considered in the context of a two-receptor translocon model for colicin entry into cells.
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Coleções:
01-internacional
Base de dados:
MEDLINE
Assunto principal:
Proteínas da Membrana Bacteriana Externa
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Ativação do Canal Iônico
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Receptores de Peptídeos
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Porinas
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Colicinas
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Transporte Proteico
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Proteínas de Escherichia coli
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Bicamadas Lipídicas
Idioma:
En
Ano de publicação:
2004
Tipo de documento:
Article