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Biophys J, February 2000, p. 761-772, Vol. 78, No. 2

Complex Voltage-Dependent Behavior of Single Unliganded Calcium-Sensitive Potassium Channels

Gargi Talukder and Richard W. Aldrich

Department of Molecular and Cellular Physiology, Howard Hughes Medical Institute, Stanford University School of Medicine, Stanford, California 94305 USA

The study and characterization of unliganded openings is of central significance for the elucidation of gating mechanisms for allosteric ligand-gated ion channels. Unliganded openings have been reported for many channel types, but their low open probability can make it difficult to study their kinetics in detail. Because the large conductance calcium-activated potassium channel mSlo is sensitive to both intracellular calcium and to membrane potential, we have been able to obtain stable unliganded single-channel recordings of mSlo with relatively high opening probability. We have found that the single-channel gating behavior of mSlo is complex, with multiple open and closed states, even when no ligand is present. Our results rule out a Monod-Wyman-Changeux allosteric mechanism with a central voltage-dependent concerted step, and they support the existence of quaternary states with less than the full number of voltage sensors activated, as has been suggested by previous work involving measurements of gating currents.

Biophys J, February 2000, p. 761-772, Vol. 78, No. 2
© 2000 by the Biophysical Society   0006-3495/00/02/761/12  $2.00


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