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    In Situ Electrochemical and PM-IRRAS Studies of Colicin El Ion Channels in the Floating Bilayer Lipid Membrane

    Year: 2019

    Journal: Langmuir, Volume 35, JUN 25, page 8452–8459

    Authors: Su, ZhangFei; Ho, Derek; Merrill, A. Rod; Lipkowski, Jacek

    Organizations: Natural Sciences and Engineering Research Council of Canada (NSERC)Natural Sciences and Engineering Research Council of Canada (NSERC) [RG-03958, RG-40001]

    Colicin E1 is a channel-forming bacteriocin produced by certain Escherichia coli cells in an effort to reduce competition from other bacterial strains. The colicin E1 channel domain was incorporated into a 1,2-diphytanoyl-sn-glycero-3-phosphocholine floating bilayer situated on a 1-thio-beta-D-glucose-modified gold (111) surface. The electrochemical properties of the colicin E1 channel in the floating bilayer were measured by electrochemical impedance spectroscopy; the configuration and orientation of colicin E1 in the bilayer were determined by polarization-modulation-infrared-reflection absorption spectroscopy. The EIS and IR results indicate that colicin E1 adopts a closed-channel state at the positive transmembrane potential, leading to high membrane resistance and a large tilt angle of alpha-helices. When the transmembrane potential becomes negative, colicin E1 begins to insert into the lipid bilayer, corresponding to low membrane resistance and a low tilt angle of alpha-helices. The insertion of colicin E1 into the lipid bilayer is driven by the negative transmembrane potential, and the ion-channel open and closed states are potential reversible. The data in this report provide new insights into the voltage-gated mechanism of colicin E1 ion channels in phospholipid bilayers and illustrate that the floating bilayer lipid membrane at the metal electrode surface is a robust platform to study membrane-active proteins and peptides in a quasi-natural environment.
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