Determinants of activation kinetics in mammalian hyperpolarization-activated cation channels

作者：Ishii TM; Takano M; Ohmori H^*

来源：The Journal of Physiology, 2001, 537(1): 93-100.

DOI：10.1111/j.1469-7793.2001.0093k.x

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 HCN 1, 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 St 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 St and S1-S2, and S6-CNBD are the crucial components for the activation gating of HCN channels.

• 出版日期2001-11-15