NMR Structural Study of the Domains of the KCNH Channels and its Insight into Channel Gating

Abstract

The voltage-gated potassium channels (KCNH) include EAG (Ether-a-go-go), ERG (EAG-related gene) and ELK (EAG-like) channels. The gating of KCNH channels is regulated by membrane potentials and these channels play important roles in cardiac repolarizaton, neuronal excitability, cellular proliferation and tumor cells. KCNH channels contain an N-terminal region formed mainly by the Per-Arnt-Sim (PAS) domain and N-cap region, six transmembrane segments (S1-S6) and a C-terminal region containing a cyclic-nucleotide-binding homology domain (CNBHD). The first four transmembrane segments (S1-S4) form the voltage-sensor domain (VSD) that is important for sensing the changes of membrane potential across the membrane a pore domain. The S5 and S6 segments form the pore domain that is responsible for the ion transport across the membrane. We are using NMR spectroscopy to explore the structures of different domains of KCNH channels such as hERG. The structures of the PAS domains of hERG and KCNH channel from Zebrafish were determined using NMR spectroscopy. To investigate the interaction between the PAS domain and the CNBHD, the solution structure of the CNBHD was also invested by NMR. Solution structure of the CNBHD of Zebrafish showed its similarity to X-ray structure. Further binding study suggested that the C-linker region of the channel might be important for interaction with PAS domain. We also carried out some NMR study on the transmembrane segments of the hERG channel, which might provide insight into gating of the KCNH channels.