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¹ Dipartimento di Biologia and Istituto di Biofisica-Consiglio Nazionale delle Ricerche, Università degli Studi di Milano, 20133 Milan, Italy
² Department of Structural Biology, University of Kiel, 24098 Kiel, Germany
³ Institute of Botany, Darmstadt University of Technology, 64287 Darmstadt, Germany

Correspondence to Anna Moroni: anna.moroni{at}unimi.it

Kcv from the chlorella virus PBCV-1 is a viral protein that forms a tetrameric, functional K⁺ channel in heterologous systems. Kcv can serve as a model system to study and manipulate basic properties of the K⁺ channel pore because its minimalistic structure (94 amino acids) produces basic features of ion channels, such as selectivity, gating, and sensitivity to blockers. We present a characterization of Kcv properties at the single-channel level. In symmetric 100 mM K⁺, single-channel conductance is 114 ± 11 pS. Two different voltage-dependent mechanisms are responsible for the gating of Kcv. "Fast" gating, analyzed by β distributions, is responsible for the negative slope conductance in the single-channel current–voltage curve at extreme potentials, like in MaxiK potassium channels, and can be explained by depletion-aggravated instability of the filter region. The presence of a "slow" gating is revealed by the very low (in the order of 1–4%) mean open probability that is voltage dependent and underlies the time-dependent component of the macroscopic current.

Abbreviations: TM, transmembrane

© 2009 Abenavoli et al.
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