RRC ID 68517
Author Ishii TM, Takano M, Ohmori H.
Title Determinants of activation kinetics in mammalian hyperpolarization-activated cation channels.
Journal J Physiol
Abstract 1. The structural basis for the different activation kinetics of hyperpolarization-activated cyclic nucleotide-gated (HCN) channels was investigated with the whole-cell patch clamp technique by using HCN1, HCN4, chimeric channels and mutants in a mammalian expression system (COS-7). 2. The activation time constant of HCN4 was about 40-fold longer than that of HCN1 when compared at -100 mV. 3. In chimeras between HCN1 and HCN4, the region of the S1 transmembrane domain and the exoplasmic S1-S2 linker markedly affected the activation kinetics. The cytoplasmic region between S6 and the cyclic nucleotide-binding domain (CNBD) also significantly affected the activation kinetics. 4. The S1 domain and S1-S2 linker of HCN1 differ from those of HCN4 at eight amino acid residues, and each single point mutation of them changed the activation kinetics less than 2-fold. However, the effects of those mutations were additive and the substitution of the whole S1 and S1-S2 region of HCN1 by that of HCN4 resulted in a 10- to 20-fold slowing. 5. The results indicate that S1 and S1-S2, and S6-CNBD are the crucial components for the activation gating of HCN channels.
Volume 537(Pt 1)
Pages 93-100
Published 2001-11-15
DOI 10.1111/j.1469-7793.2001.0093k.x
PII PHY_12629
PMID 11711564
PMC PMC2278938
MeSH Animals COS Cells Cations / metabolism* Chimera Cyclic Nucleotide-Gated Cation Channels Electrophysiology Hyperpolarization-Activated Cyclic Nucleotide-Gated Channels Ion Channels / genetics Ion Channels / physiology* Kinetics Mice Muscle Proteins* Nerve Tissue Proteins* Point Mutation Potassium Channels Protein Structure, Tertiary / physiology Rabbits Time Factors
Human and Animal Cells COS-7(RCB0539)