Anomalous proton selectivity in a large channel: Colicin A

Stephen L. Slatin, Alan Finkelstein, Paul K. Kienker

Research output: Contribution to journalArticle

8 Citations (Scopus)

Abstract

Some of the bactericidal proteins known as colicins exert their toxic action by forming a large, nonselective channel in the inner membrane of target bacteria. The structure of this channel is unknown. It conducts large ions but has a much smaller conductance than would be expected for a channel of its deduced size. Here we report that the colicin channel, particularly the colicin A channel, is selective for protons over other cations (and anions) by many orders of magnitude. This was deduced from measurements of reversal potentials in pH gradients across planar lipid bilayers containing these channels. For example, in symmetric 0.1 M KCl with a pH 5/pH 8 gradient across the membrane, the reversal potential of colicin A is -21 mV, rather than 0. Such a result would be unremarkable for a narrow channel but is beyond explanation by current understanding of permeation for a channel of its diameter. For this reason, we re-examined the issue of the diameter of the channel lumen and confirmed that the lumen is indeed "too large" (∼10 Å) to select for protons by the amount that we measure. We are thus compelled to propose that an unorthodox mechanism is at work in this protein.

Original languageEnglish (US)
Pages (from-to)1778-1788
Number of pages11
JournalBiochemistry
Volume47
Issue number6
DOIs
StatePublished - Feb 12 2008

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Colicins
Protons
Proton-Motive Force
Membranes
Toxic Actions
Lipid bilayers
Lipid Bilayers
Heavy ions
Permeation
Membrane Potentials
Anions
Cations
Bacteria
Proteins
Ions

ASJC Scopus subject areas

  • Biochemistry

Cite this

Slatin, S. L., Finkelstein, A., & Kienker, P. K. (2008). Anomalous proton selectivity in a large channel: Colicin A. Biochemistry, 47(6), 1778-1788. https://doi.org/10.1021/bi701900x

Anomalous proton selectivity in a large channel : Colicin A. / Slatin, Stephen L.; Finkelstein, Alan; Kienker, Paul K.

In: Biochemistry, Vol. 47, No. 6, 12.02.2008, p. 1778-1788.

Research output: Contribution to journalArticle

Slatin, SL, Finkelstein, A & Kienker, PK 2008, 'Anomalous proton selectivity in a large channel: Colicin A', Biochemistry, vol. 47, no. 6, pp. 1778-1788. https://doi.org/10.1021/bi701900x
Slatin SL, Finkelstein A, Kienker PK. Anomalous proton selectivity in a large channel: Colicin A. Biochemistry. 2008 Feb 12;47(6):1778-1788. https://doi.org/10.1021/bi701900x
Slatin, Stephen L. ; Finkelstein, Alan ; Kienker, Paul K. / Anomalous proton selectivity in a large channel : Colicin A. In: Biochemistry. 2008 ; Vol. 47, No. 6. pp. 1778-1788.
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