Chimeric hERG Channels Containing a Tetramerization Domain are Functional and Stable

Biochemical and detailed structural information of human ether-a-go-go-related gene (hERG) potassium channels are scarce but are a prerequisite to understand the unwanted interactions of hERG with drugs and the effect of mutations that lead to long QT syndrome. Despite the huge interest in hERG, to our knowledge, procedures that provide a purified, functional, and tetrameric hERG channel are not available. Here, we describe hybrid hERG molecules, termed chimeric hERG channels, in which the N-terminal Per-Arnt-Sim (PAS) domain is deleted and the C-terminal C-linker as well as the cyclic nucleotide binding domain (CNBD) portion is replaced by an artificial tetramerization domain. These chimeric hERG channels can be overexpressed in HEK cells, solubilized in detergent, and purified as tetramers. When expressed in Xenopus laevis oocytes, the chimeric channels exhibit efficient trafficking to the cell surface, whereas a hERG construct lacking the PAS and C-linker/CNBD domains is retained in the cytoplasm. The chimeric hERG channels retain essential hERG functions such as voltage-dependent gating and inhibition by astemizole and the scorpion toxin BeKm-1. The chimeric channels are thus powerful tools for helping to understand the contribution of the cytoplasmic hERG domains to the gating process and are suitable for in vitro biochemical and structural studies.