title: Demonstration of physical proximity between the N terminus and the S4-S5 linker of the human ether-a-go-go-related gene (hERG) potassium channel.
abstract: Potassium channels encoded by the human ether-à-go-go-related gene (hERG) contribute to cardiac repolarization as a result of their characteristic gating properties. The hERG channel N terminus acts as a crucial determinant in gating. It is also known that the S4-S5 linker couples the voltage-sensing machinery to the channel gate. Moreover, this linker has been repeatedly proposed as an interaction site for the distal portion of the N terminus controlling channel gating, but direct evidence for such an interaction is still lacking. In this study, we used disulfide bond formation between pairs of engineered cysteines to demonstrate the close proximity between the beginning of the N terminus and the S4-S5 linker. Currents from channels with introduced cysteines were rapidly and strongly attenuated by an oxidizing agent, this effect being maximal for cysteine pairs located around amino acids 3 and 542 of the hERG sequence. The state-dependent modification of the double-mutant channels, but not the single-cysteine mutants, and the ability to readily reverse modification with the reducing agent dithiothreitol indicate that a disulfide bond is formed under oxidizing conditions, locking the channels in a non-conducting state. We conclude that physical interactions between the N-terminal-most segment of the N terminus and the S4-S5 linker constitute an essential component of the hERG gating machinery, thus providing a molecular basis for previous data and indicating an important contribution of these cytoplasmic domains in controlling its unusual gating and hence determining its physiological role in setting the electrical behavior of cardiac and other cell types.
authors.affiliation: Department of Biochemistry and Molecular Biology, University of Oviedo, 33006 Oviedo, Spain.
authors.forename: Pilar
authors.initials: P
authors.lastname: de la Peña
authors.forename: Carlos
authors.initials: C
authors.lastname: Alonso-Ron
authors.forename: Angeles
authors.initials: A
authors.lastname: Machín
authors.forename: Jorge
authors.initials: J
authors.lastname: Fernández-Trillo
authors.forename: Luis
authors.initials: L
authors.lastname: Carretero
authors.forename: Pedro
authors.initials: P
authors.lastname: Domínguez
authors.forename: Francisco
authors.initials: F
authors.lastname: Barros
mesh_terms: D019943:Amino Acid Substitution; D000818:Animals; D000072237:ERG1 Potassium Channel; D051638:Ether-A-Go-Go Potassium Channels / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D015640:Ion Channel Gating / Q000502:physiology*; D020125:Mutation, Missense; D017434:Protein Structure, Tertiary; D014982:Xenopus laevis
chemical_list: D000072237:ERG1 Potassium Channel; D051638:Ether-A-Go-Go Potassium Channels; C000606913:KCNH2 protein, human