title: Tuning the tetraethylammonium sensitivity of potassium channel Kcv by subunit combination.
abstract: Tetraethylammonium (TEA) is a potassium (K(+)) channel inhibitor that has been extensively used as a molecular probe to explore the structure of channels' ion pathway. In this study, we identified that Leu70 of the virus-encoded potassium channel Kcv is a key amino acid that plays an important role in regulating the channel's TEA sensitivity. Site-directed mutagenesis of Leu70 can change the TEA sensitivity by 1,000-fold from ∼100 µM to ∼100 mM. Because no compelling trends exist to explain this amino acid's specific interaction with TEA, the role of Leu70 at the binding site is likely to ensure an optimal conformation of the extracellular mouth that confers high TEA affinity. We further assembled the subunits of mutant and wt-Kcv into a series of heterotetramers. The differences in these heterochannels suggest that all of the four subunits in a Kcv channel additively participate in the TEA binding, and each of the four residues at the binding site independently contributes an equal binding energy. We therefore can present a series of mutant/wild-type tetramer combinations that can probe TEA over three orders of magnitude in concentration. This study may give insight into the mechanism for the interaction between the potassium channel and its inhibitor.
authors.affiliation: Department of Biological Engineering, University of Missouri, Columbia, MO 65211, USA.
authors.forename: Qiulin
authors.initials: Q
authors.lastname: Tan
authors.forename: Brandon
authors.initials: B
authors.lastname: Ritzo
authors.forename: Kai
authors.initials: K
authors.lastname: Tian
authors.forename: Li-Qun
authors.initials: LQ
authors.lastname: Gu
mesh_terms: D000595:Amino Acid Sequence; D004305:Dose-Response Relationship, Drug; D015640:Ion Channel Gating / Q000187:drug effects* / Q000502:physiology*; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D015221:Potassium Channels / Q000737:chemistry / Q000502:physiology*; D021122:Protein Subunits; D013329:Structure-Activity Relationship; D019789:Tetraethylammonium / Q000008:administration & dosage*; D014764:Viral Proteins / Q000037:antagonists & inhibitors* / Q000737:chemistry / Q000502:physiology*
chemical_list: C405463:Kcv potassium channel, Chlorella virus; D015221:Potassium Channels; D021122:Protein Subunits; D014764:Viral Proteins; D019789:Tetraethylammonium