title: The carboxyl tail forms a discrete functional domain that blocks closure of the yeast K+ channel.
abstract: Non-targeted mutagenesis studies of the yeast K(+) channel, TOK1, have led to identification of functional domains common to other cation channels as well as those so far not found in other channels. Among the latter is the ability of the carboxyl tail to prevent channel closure. Here, we show that the tail can fulfill this function in trans. Coexpression of the carboxyl tail with the tail-deleted channel core restores normal channel behavior A Ser/Thr-rich region at its amino end and an acidic stretch at its carboxyl end delineate the minimal region required for tail function. This region of 160 aa apparently forms a discrete functional domain. Interaction of this domain with the channel core is strong, being recalcitrant to removal from excised membrane patches by both high salt and reducing agents. Although the use of a cytoplasmic domain to regulate channel is common among animal channels, by using it as a "foot-in-the-door" to maintain open state appears unique to TOK1, the first fungal K(+) channel studied in depth.
authors.affiliation: Laboratory of Molecular Biology, University of Wisconsin, Madison, WI 53706, USA. shloukin@facstaff.wisc.edu
authors.forename: Stephen H
authors.initials: SH
authors.lastname: Loukin
authors.forename: Junyu
authors.initials: J
authors.lastname: Lin
authors.forename: Umair
authors.initials: U
authors.lastname: Athar
authors.forename: Christopher
authors.initials: C
authors.lastname: Palmer
authors.forename: Yoshiro
authors.initials: Y
authors.lastname: Saimi
mesh_terms: D000595:Amino Acid Sequence; D002118:Calcium / Q000378:metabolism; D003593:Cytoplasm / Q000378:metabolism; D004247:DNA / Q000378:metabolism; D019281:Dimerization; D004594:Electrophysiology; D017353:Gene Deletion; D008954:Models, Biological; D008969:Molecular Sequence Data; D016296:Mutagenesis; D010766:Phosphorylation; D010957:Plasmids / Q000378:metabolism; D015221:Potassium Channels / Q000737:chemistry* / Q000378:metabolism*; D017434:Protein Structure, Tertiary; D012313:RNA / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000235:genetics; D029701:Saccharomyces cerevisiae Proteins; D017386:Sequence Homology, Amino Acid
chemical_list: D015221:Potassium Channels; D029701:Saccharomyces cerevisiae Proteins; C095220:TOK1 protein, S cerevisiae; D012313:RNA; D004247:DNA; D002118:Calcium