Biophysical Journal 61: 736-749 (1992)
© 1992 the Biophysical Society

This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Tyerman, S D Articles by Findlay, G P Search for Related Content PubMed PubMed Citation Articles by Tyerman, S D Articles by Findlay, G P

Multiple conductances in the large K+ channel from Chara corallina shown by a transient analysis method.

School of Biological Sciences, Flinders University of South Australia, Bedford Park.

ABSTRACT

The large conductance K+ channel in the tonoplast of Chara corallina has subconductance states (substates). We describe a method that detects substates by monitoring the time derivative of channel current. Substates near to the full conductance tend to have long durations and high probabilities, while those of smaller amplitude occur with less probability and short duration. The substate pattern is similar in cell-attached, inside-out and outside-out patches over a range of temperatures. The pattern changes at high Ca2+ concentration (10 mol m-3) on the cytoplasmic face of inside-out patches. One substate at approximately 50% of the full conductance is characterized by a high frequency of transitions from the full conductance level. This midstate conductance is not a constant proportion of the full conductance but changes as a function of membrane potential difference (p.d.) showing strong inward rectification. We suggest that the channel is a single pore that can change conformation and/or charge profile to give different conductances. The mean durations of the full conductance level and the midstate decrease as the membrane p.d. becomes more negative. Programs for analysis of channel kinetics based on an half-amplitude detection criterion are shown to be unsuitable for analysis of the K+ channel.

This article has been cited by other articles:

				G. Obermeyer and S. D. Tyerman NH4+ Currents across the Peribacteroid Membrane of Soybean. Macroscopic and Microscopic Properties, Inhibition by Mg2+, and Temperature Dependence Indicate a SubpicoSiemens Channel Finely Regulated by Divalent Cations Plant Physiology, October 1, 2005; 139(2): 1015 - 1029. [Abstract] [Full Text] [PDF]

				F. Qin Restoration of Single-Channel Currents Using the Segmental k-Means Method Based on Hidden Markov Modeling Biophys. J., March 1, 2004; 86(3): 1488 - 1501. [Abstract] [Full Text] [PDF]

				S.-H. Chung, T. W. Allen, and S. Kuyucak Modeling Diverse Range of Potassium Channels with Brownian Dynamics Biophys. J., July 1, 2002; 83(1): 263 - 277. [Abstract] [Full Text] [PDF]

				W.-H. Zhang, M. Skerrett, N. A. Walker, J. W. Patrick, and S. D. Tyerman Nonselective Currents and Channels in Plasma Membranes of Protoplasts from Coats of Developing Seeds of Bean Plant Physiology, February 1, 2002; 128(2): 388 - 399. [Abstract] [Full Text] [PDF]

				M. Root and R MacKinnon Two identical noninteracting sites in an ion channel revealed by proton transfer Science, September 23, 1994; 265(5180): 1852 - 1856. [Abstract] [PDF]