QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text Full Text (PDF) Data Supplement All Versions of this Article: mol.107.042085v1 73/6/1643    most recent Submit a response Alert me when this article is cited Alert me when eLetters are posted Alert me if a correction is posted Services Related articles in MolPharm 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 Myokai, T. Articles by Oiki, S. Search for Related Content PubMed PubMed Citation Articles by Myokai, T. Articles by Oiki, S.

Topological Mapping of the Asymmetric Drug Binding to the Human Ether-à-go-go-Related Gene Product (HERG) Potassium Channel by Use of Tandem Dimers

Department of Molecular Physiology and Biophysics, Faculty of Medical Sciences, University of Fukui, Fukui, Japan (T.M., H.S., S.O.); and Pharmaceutical Research Division, Takeda Pharmaceutical Company Limited, Osaka, Japan (T.M., S.R.)

The human ether-à-go-go related gene product (HERG) channel is essential for electrical activity of heart cells, and block of this channel by many drugs leads to lethal arrhythmias. Tyr₆₅₂ and Phe₆₅₆ of the sixth transmembrane helix are candidates for the drug binding site. In the tetrameric HERG channel, a drug with asymmetric structure should interact unevenly with multiple residues from different subunits. To elucidate the topology of the drug-binding site, we constructed tandem dimers of HERG channels and the aromatic Tyr₆₅₂ and Phe₆₅₆ residues were replaced by alanine singly or doubly. Eight types of HERG channels, including homotetrameric mutants, having different numbers and arrangements of aromatic residues at the blocking site, were studied. Effects of cisapride on channels expressed in Xenopus laevis oocytes were examined electrophysiologically. The inhibition constants (K_i) were increased significantly as the diagonal Tyr₆₅₂ were deleted, whereas those for the diagonal Phe₆₅₆-deleted mutant were not changed. These results suggest that Tyr₆₅₂ residues from adjacent subunits contributed to the binding. Two types of double mutants of tandem dimers showed significantly distinct affinities, suggesting that the coexistence of Tyr₆₅₂ and Phe₆₅₆ on a subunit in diagonal position is crucial to having a high affinity. Thermodynamic double-mutant cycle analyses revealed interactions between Tyr₆₅₂ and Phe₆₅₆ upon binding. The kinetics and voltage-dependence of blocking suggested transitions of the binding site from low to high affinity. These approaches using a set of mutant HERG channels gave a dynamic picture of the spatial arrangements of residues that contribute to the drug-channel interaction.

Address correspondence to: Shigetoshi Oiki, Department of Molecular Physiology and Biophysics, Faculty of Medical Sciences, University of Fukui, 23-3 Matsuokashimoaizuki, Eiheiji-cho, Yoshida-gun, Fukui 910-1193, Japan. E-mail: oiki-fki{at}umin.ac.jp

Related articles in MolPharm:

Refining Insights into High-Affinity Drug Binding to the Human Ether-à-go-go-Related Gene Potassium Channel

Jules C. Hancox and Andrew F. James
MolPharm 2008 73: 1592-1595. [Abstract] [Full Text]  

This article has been cited by other articles:

				M. J. Perrin, P. W. Kuchel, T. J. Campbell, and J. I. Vandenberg Drug Binding to the Inactivated State Is Necessary but Not Sufficient for High-Affinity Binding to Human Ether-a-go-go-Related Gene Channels Mol. Pharmacol., November 1, 2008; 74(5): 1443 - 1452. [Abstract] [Full Text] [PDF]

				J. C. Hancox and A. F. James Refining Insights into High-Affinity Drug Binding to the Human Ether-a-go-go-Related Gene Potassium Channel Mol. Pharmacol., June 1, 2008; 73(6): 1592 - 1595. [Abstract] [Full Text] [PDF]