|
|
|
|
|
|
|
||
Address correspondence to Gea-Ny Tseng, Dept. of Physiology, Virginia Commonwealth University, 1101 E. Marshall St., Richmond, VA 23298. Fax: (804)828-7382. email: gtseng{at}hsc.vcu.edu
The hERG channel has a relatively slow activation process but an extremely fast and voltage-sensitive inactivation process. Direct measurement of hERG's gating current (Piper, D.R., A. Varghese, M.C. Sanguinetti, and M. Tristani-Firouzi. 2003. PNAS. 100:10534–10539) reveals two kinetic components of gating charge transfer that may originate from two channel domains. This study is designed to address three questions: (1) which of the six positive charges in hERG's major voltage sensor, S4, are responsible for gating charge transfer during activation, (2) whether a negative charge in the cytoplasmic half of S2 (D466) also contributes to gating charge transfer, and (3) whether S4 serves as the sole voltage sensor for hERG inactivation. We individually mutate S4's positive charges and D466 to cysteine, and examine (a) effects of mutations on the number of equivalent gating charges transferred during activation (za) and inactivation (zi), and (b) sidedness and state dependence of accessibility of introduced cysteine side chains to a membrane-impermeable thiol-modifying reagent (MTSET). Neutralizing the outer three positive charges in S4 and D466 in S2 reduces za, and cysteine side chains introduced into these positions experience state-dependent changes in MTSET accessibility. On the other hand, neutralizing the inner three positive charges in S4 does not affect za. None of the charge mutations affect zi. We propose that the scheme of gating charge transfer during hERG's activation process is similar to that described for the Shaker channel, although hERG has less gating charge in its S4 than in Shaker. Furthermore, channel domain other than S4 contributes to gating charge involved in hERG's inactivation process.
Key Words: voltage-gated K+ channel • ion channel gating • mutagenesis • Xenopus oocyte • voltage sensor
Abbreviation used in this paper: WT, wild type.
CiteULike 
Complore 
Connotea 
Del.icio.us 
Digg 
Reddit 
Technorati What's this?
This article has been cited by other articles:
|
|
 |
|
  T. L. Klassen, M. L. O'Mara, M. Redstone, A. N. Spencer, and W. J. Gallin Non-linear intramolecular interactions and voltage sensitivity of a KV1 family potassium channel from Polyorchis penicillatus (Eschscholtz 1829) J. Exp. Biol., November 1, 2008; 211(21): 3442 - 3453. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 G. Panaghie, K. Purtell, K.-K. Tai, and G. W. Abbott Voltage-Dependent C-Type Inactivation in a Constitutively Open K+ Channel Biophys. J., September 15, 2008; 95(6): 2759 - 2778. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
C. Alonso-Ron, P. de la Pena, P. Miranda, P. Dominguez, and F. Barros Thermodynamic and Kinetic Properties of Amino-Terminal and S4-S5 Loop HERG Channel Mutants under Steady-State Conditions Biophys. J., May 15, 2008; 94(10): 3893 - 3911. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 J. I. Vandenberg, A. Varghese, Y. Lu, J. A. Bursill, M. P. Mahaut-Smith, and C. L.-H. Huang Temperature dependence of human ether-a-go-go-related gene K+ currents Am J Physiol Cell Physiol, July 1, 2006; 291(1): C165 - C175. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 Z. Ma, X. J. Lou, and F. T. Horrigan Role of Charged Residues in the S1-S4 Voltage Sensor of BK Channels J. Gen. Physiol., February 27, 2006; 127(3): 309 - 328. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 R. N. Subbiah, M. Kondo, T. J. Campbell, and J. I. Vandenberg Tryptophan scanning mutagenesis of the HERG K+ channel: the S4 domain is loosely packed and likely to be lipid exposed J. Physiol., December 1, 2005; 569(2): 367 - 379. [Abstract] [Full Text] [PDF]
|
|
|
|
