title: Interrogation of the intersubunit interface of the open Hv1 proton channel with a probe of allosteric coupling.
abstract: The Hv1 voltage-gated proton channel is a dimeric complex consisting of two voltage-sensing domains (VSDs), each containing a gated proton permeation pathway. Dimerization is controlled by a cytoplasmic coiled-coil domain. The transitions from the closed to the open state in the two VSDs are known to occur cooperatively; however, the underlying mechanism is poorly understood. Intersubunit interfaces play a critical role in allosteric processes; but, such interfaces have not been determined in the open Hv1 channel. Here we show that 2-guanidinothiazole derivatives block the two Hv1 VSDs in a cooperative way, and use one of the compounds as a probe of allosteric coupling between open subunits. We find that the extracellular ends of the first transmembrane segments of the VSDs form the intersubunit interface that mediates coupling between binding sites, while the coiled-coil domain does not directly participate in the process. We also find strong evidence that the channel's proton selectivity filter controls blocker binding cooperativity.
authors.affiliation: Department of Physiology and Biophysics, University of California, Irvine, CA 92697, USA.
authors.forename: Liang
authors.initials: L
authors.lastname: Hong
authors.affiliation: Department of Pharmacology, University of California, Davis, CA 95616, USA.
authors.forename: Vikrant
authors.initials: V
authors.lastname: Singh
authors.affiliation: Department of Pharmacology, University of California, Davis, CA 95616, USA.
authors.forename: Heike
authors.initials: H
authors.lastname: Wulff
authors.affiliation: Department of Physiology and Biophysics, University of California, Irvine, CA 92697, USA.
authors.forename: Francesco
authors.initials: F
authors.lastname: Tombola
mesh_terms: D000494:Allosteric Regulation; D001665:Binding Sites; D019281:Dimerization; D006801:Humans; D007473:Ion Channels / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism; D016297:Mutagenesis, Site-Directed; D020836:Protein Structure, Quaternary; D017434:Protein Structure, Tertiary; D021122:Protein Subunits / Q000737:chemistry / Q000378:metabolism; D013844:Thiazoles / Q000737:chemistry* / Q000378:metabolism
chemical_list: C510235:HVCN1 protein, human; D007473:Ion Channels; D021122:Protein Subunits; D013844:Thiazoles