|
|
|
|
|
|
|
||
From the Department of Molecular and Cellular Physiology, and Howard Hughes Medical Institute, Stanford University, Stanford
California 94305
In this and the following paper we have examined the kinetic and steady-state properties of macroscopic mslo Ca-activated K+ currents in order to interpret these currents in terms of the gating behavior of the mslo
channel. To do so, however, it was necessary to first find conditions by which we could separate the effects that
changes in Ca2+ concentration or membrane voltage have on channel permeation from the effects these stimuli
have on channel gating. In this study we investigate three phenomena which are unrelated to gating but are manifest in macroscopic current records: a saturation of single channel current at high voltage, a rapid voltage-dependent Ca2+ block, and a slow voltage-dependent Ba2+ block. Where possible methods are described by which these
phenomena can be separated from the effects that changes in Ca2+ concentration and membrane voltage have on
channel gating. Where this is not possible, some assessment of the impact these effects have on gating parameters
determined from macroscopic current measurements is provided. We have also found that without considering the effects of Ca2+ and voltage on channel permeation and block, macroscopic current measurements suggest
that mslo channels do not reach the same maximum open probability at all Ca2+ concentrations. Taking into account permeation and blocking effects, however, we find that this is not the case. The maximum open probability of the mslo channel is the same or very similar over a Ca2+ concentration range spanning three orders of magnitude indicating that over this range the internal Ca2+ concentration does not limit the ability of the channel to be activated by voltage.
CiteULike 
Complore 
Connotea 
Del.icio.us 
Digg 
Reddit 
Technorati What's this?
This article has been cited by other articles:
|
|
 |
|
  I. Schroeder and U.-P. Hansen Saturation and Microsecond Gating of Current Indicate Depletion-induced Instability of the MaxiK Selectivity Filter J. Gen. Physiol., July 1, 2007; 130(1): 83 - 97. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
Y. Li, I. Berke, L. Chen, and Y. Jiang Gating and Inward Rectifying Properties of the MthK K+ Channel with and without the Gating Ring J. Gen. Physiol., January 29, 2007; 129(2): 109 - 120. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
B. Wang and R. Brenner An S6 Mutation in BK Channels Reveals {beta}1 Subunit Effects on Intrinsic and Voltage-dependent Gating J. Gen. Physiol., December 1, 2006; 128(6): 731 - 744. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
H. Zeng, T. M. Weiger, H. Fei, and I. B. Levitan Mechanisms of Two Modulatory Actions of the Channel-binding Protein Slob on the Drosophila Slowpoke Calcium-dependent Potassium Channel J. Gen. Physiol., November 1, 2006; 128(5): 583 - 591. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
W. Li and R. W. Aldrich State-dependent Block of BK Channels by Synthesized Shaker Ball Peptides J. Gen. Physiol., October 1, 2006; 128(4): 423 - 441. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
C. M. Wilkens and R. W. Aldrich State-independent Block of BK Channels by an Intracellular Quaternary Ammonium J. Gen. Physiol., August 28, 2006; 128(3): 347 - 364. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
B. Wang, B. S. Rothberg, and R. Brenner Mechanism of {beta}4 Subunit Modulation of BK Channels J. Gen. Physiol., March 27, 2006; 127(4): 449 - 465. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
L. Hu, H. Yang, J. Shi, and J. Cui Effects of Multiple Metal Binding Sites on Calcium and Magnesium-dependent Activation of BK Channels J. Gen. Physiol., December 27, 2005; 127(1): 35 - 50. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
L. Bao and D. H. Cox Gating and Ionic Currents Reveal How the BKCa Channel's Ca2+ Sensitivity Is Enhanced by its {beta}1 Subunit J. Gen. Physiol., September 26, 2005; 126(4): 393 - 412. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
T. I. Brelidze and K. L. Magleby Probing the Geometry of the Inner Vestibule of BK Channels with Sugars J. Gen. Physiol., July 25, 2005; 126(2): 105 - 121. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
G. Zhang and F. T. Horrigan Cysteine Modification Alters Voltage- and Ca2+-dependent Gating of Large Conductance (BK) Potassium Channels J. Gen. Physiol., January 31, 2005; 125(2): 213 - 236. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
W. Li and R. W. Aldrich Unique Inner Pore Properties of BK Channels Revealed by Quaternary Ammonium Block J. Gen. Physiol., June 28, 2004; 124(1): 43 - 57. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
T. I. Brelidze and K. L. Magleby Protons Block BK Channels by Competitive Inhibition with K+ and Contribute to the Limits of Unitary Currents at High Voltages J. Gen. Physiol., February 23, 2004; 123(3): 305 - 319. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
F. T. Horrigan and R. W. Aldrich Coupling between Voltage Sensor Activation, Ca2+ Binding and Channel Opening in Large Conductance (BK) Potassium Channels J. Gen. Physiol., August 26, 2002; 120(3): 267 - 305. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 R. Brenner, T. J. Jegla, A. Wickenden, Y. Liu, and R. W. Aldrich Cloning and Functional Characterization of Novel Large Conductance Calcium-activated Potassium Channel beta Subunits, hKCNMB3 and hKCNMB4 J. Biol. Chem., February 25, 2000; 275(9): 6453 - 6461. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
L. Diaz, P. Meera, J. Amigo, E. Stefani, O. Alvarez, L. Toro, and R. Latorre Role of the S4 Segment in a Voltage-dependent Calcium-sensitive Potassium (hSlo) Channel J. Biol. Chem., December 4, 1998; 273(49): 32430 - 32436. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 D. A. Sullivan, M. H. Holmqvist, and I. B. Levitan Characterization of Gating and Peptide Block of mSlo, a Cloned Calcium-Dependent Potassium Channel J Neurophysiol, December 1, 1997; 78(6): 2937 - 2950. [Abstract] [Full Text] [PDF]
|
|
|
|
