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Open AccessArticle

Cooperativity and Steep Voltage Dependence in a Bacterial Channel

Department of Biology, University of Maryland, College Park, MD 20742, USA
Author to whom correspondence should be addressed.
Int. J. Mol. Sci. 2019, 20(18), 4501;
Received: 12 August 2019 / Revised: 2 September 2019 / Accepted: 4 September 2019 / Published: 11 September 2019
(This article belongs to the Collection Feature Papers in Molecular Biophysics)
This paper reports on the discovery of a novel three-membrane channel unit exhibiting very steep voltage dependence and strong cooperative behavior. It was reconstituted into planar phospholipid membranes formed by the monolayer method and studied under voltage-clamp conditions. The behavior of the novel channel-former, isolated from Escherichia coli, is consistent with a linearly organized three-channel unit displaying steep voltage-gating (a minimum of 14 charges in the voltage sensor) that rivals that of channels in mammalian excitable membranes. The channels also display strong cooperativity in that closure of the first channel permits the second to close and closure of the second channel permits closure of the third. All three have virtually the same conductance and selectivity, and yet the first and third close at positive potentials whereas the second closes at negative potentials. Thus, is it likely that the second channel-former is oriented in the membrane in a direction opposite to that of the other two. This novel structure is named “triplin.” The extraordinary behavior of triplin indicates that it must have important and as yet undefined physiological roles.
Keywords: Escherichia coli; planar membrane; pore; dipole; electrophysiology; voltage gating Escherichia coli; planar membrane; pore; dipole; electrophysiology; voltage gating
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MDPI and ACS Style

Lin, S.H.; Chang, K.-T.; Cherian, N.; Wu, B.; Phee, H.; Cho, C.; Colombini, M. Cooperativity and Steep Voltage Dependence in a Bacterial Channel. Int. J. Mol. Sci. 2019, 20, 4501.

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