Molecular Biochemistry I

K+ Channels

Reading:

Textbook Reading: Biochemistry, 3rd Edition, by Voet & Voet, Chapter 20 (especially p. 735-738).

Some recent articles (optional reading): 
Y. Jiang, A. Lee, J. Chen, V. Ruta, M. Cadene, B. T. Chait & R. MacKinnon (2003) "X-ray structure of a voltage-dependent K+ channel," Nature 423: 33-41.
R. MacKinnon (2003) "Potassium channels," FEBS Lett. 555: 62-65.
G. V. Miloshevsky & P. C. Jordan (2004) "Permeation in ion channels: the interplay of structure and theory," Trends in Neurosci. 27: 308-314.
B. Roux (2005) "Ion conduction and selectivity in K+ channels," Annu. Rev. Biophys. Biomol. Struct. 34: 153-171.
S. B. Long, E. B. Campbell & R. MacKinnon (2005) "Crystal structure of a mammalian voltage-dependent Shaker family K+ channel," Science 309: 897-902.
S. B. Long, E. B. Campbell & R. MacKinnon (2005) "Voltage sensor of Kv1.2: structural basis of electromechanical coupling," Science 309: 903-908.
S. H. Loukin, M. M.-C. Kuo, X.-L. Zhou, W. J. Haynes, C. Kung & Y. Saimi (2005) "Microbial K+ Channels," J. Gen. Physiol. 125: 521-527.
F. Tombola, M. M. Pathak & E. Y. Isacoff (2006) "How does voltage open an ion channel?" Annu. Rev. Cell Dev. Biol. 22: 23-52.
H. T. Kurata & D. Fedida (2006) "A structural interpretation of voltage-gated potassium channel inactivation," Progr. Biophys. Molec. Biol. 92: 185-208.
S. B. Long, X. Tao, E. B. Campbell & R. MacKinnon (2007) "Atomic structure of a voltage-dependent K+ channel in a lipid membrane-like environment," Nature: 450: 376-382.

Potential Test Question:

a. A consensus sequence is part of the primary structure of all K+ channels. On the diagram of the bacterial KcsA K+ channel at right, indicate the location of the consensus sequence. Describe the structure and role of the consensus sequence domain, and the nature of its interaction with K+. Why is the energy barrier for entry of K+ into the channel low?
b. Indicate on the diagram the location of the channel gate. Is this the closed or open conformation of the channel? Based on your knowledge of other solved K+ channel structures (e.g., that of the
MthK channel in the presence of Ca++), describe the conformation change that occurs during channel gating. What residue in one of the transmembrane a-helices is essential to this conformational change in the MthK channel, and what is its role?

Copyright 1998-2008 by Joyce J. Diwan. All rights reserved.

Lecture notes on
Potassium Channels

Interactive Quiz on   

K+ Channels       
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