title: Membrane anchoring and interaction between transmembrane domains are crucial for K+ channel function.
abstract: The small viral channel Kcv is a Kir-like K(+) channel of only 94 amino acids. With this simple structure, the tetramer of Kcv represents the pore module of all complex K(+) channels. To examine the structural contribution of the transmembrane domains (TMDs) to channel function, we performed Ala scanning mutagenesis of the two domains and tested the functionality of the mutants in a yeast complementation assay. The data reveal, in combination with computational models, that the upper halves of both TMDs, which face toward the external medium, are rather rigid, whereas the inner parts are more flexible. The rigidity of the outer TMD is conferred by a number of essential aromatic amino acids that face the membrane and probably anchor this domain in the bilayer. The inner TMD is intimately connected with the rigid part of the outer TMD via π···π interactions between a pair of aromatic amino acids. This structural principle is conserved within the viral K(+) channels and also present in Kir2.2, implying a general importance of this architecture for K(+) channel function.
authors.affiliation: Institute of Botany, Technische Universität Darmstadt, Darmstadt, Germany.
authors.forename: Manuela
authors.initials: M
authors.lastname: Gebhardt
authors.forename: Franziska
authors.initials: F
authors.lastname: Hoffgaard
authors.forename: Kay
authors.initials: K
authors.lastname: Hamacher
authors.forename: Stefan M
authors.initials: SM
authors.lastname: Kast
authors.forename: Anna
authors.initials: A
authors.lastname: Moroni
authors.forename: Gerhard
authors.initials: G
authors.lastname: Thiel
mesh_terms: D019943:Amino Acid Substitution; D000818:Animals; D005816:Genetic Complementation Test; D006801:Humans; D008051:Lipid Bilayers / Q000737:chemistry / Q000378:metabolism; D008958:Models, Molecular; D020125:Mutation, Missense; D015221:Potassium Channels / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D017434:Protein Structure, Tertiary; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism; D013329:Structure-Activity Relationship; D014764:Viral Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism
chemical_list: D008051:Lipid Bilayers; D015221:Potassium Channels; D014764:Viral Proteins