Increased salt concentration promotes competitive block of OmpF channel by protons
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Other documents of the author: Alcaraz, Antonio; García Giménez, Elena; Aguilella, Vicente; Queralt-Martín, María
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comunitat-uji-handle2:10234/2507
comunitat-uji-handle3:10234/6973
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Title
Increased salt concentration promotes competitive block of OmpF channel by protonsDate
2012-11Publisher
ElsevierType
info:eu-repo/semantics/articleVersion
info:eu-repo/semantics/publishedVersionSubject
Abstract
Porins are channel-forming proteins that are located in the outer membranes (OM) of Gram-negative bacteria
and allow the influx of hydrophilic nutrients and the extrusion of waste products. The fine regulation of ... [+]
Porins are channel-forming proteins that are located in the outer membranes (OM) of Gram-negative bacteria
and allow the influx of hydrophilic nutrients and the extrusion of waste products. The fine regulation of the
ion transport through these wide channels could play an important role in the survival of the bacteria in acidic
media. We investigate here the mechanism responsible for the pH sensitivity of the trimeric porin OmpF,
of Escherichia coli. Planar lipid bilayer electrophysiology and site-directed mutagenesis were used to
study the effect of pH on the ion conductive properties of the OmpF channel in its fully open, “nongated”
conformation. At low pH we observe a large drop in the OmpF open channel conductance that is accompanied
by a substantial increase of the current noise. These channel features are strongly dependent on the salt
concentration and we propose that they are originated by competitive binding of cations and protons occurring
in the narrow central constriction of the channel. This subtlemechanismreveals to be capital for the channel
function because it not only drives the channel sensitivity to pH but is also indispensable for the particularly
efficient permeation mechanism of the channel at physiological conditions (~neutral pH). [-]
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Biochimica et Biophysica Acta (Biomembranes), v. 1818, issue 11 (November 2012)Rights
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