title: KTN (RCK) domains regulate K+ channels and transporters by controlling the dimer-hinge conformation.
abstract: KTN (RCK) domains are nucleotide-binding folds that form the cytoplasmic regulatory complexes of various K+ channels and transporters. The mechanisms these proteins use to control their transmembrane pore-forming counterparts remains unclear despite numerous electrophysiological and structural studies. KTN (RCK) domains consistently crystallize as dimers within the asymmetric unit, forming a pronounced hinge between two Rossmann folds. We have previously proposed that modification of the hinge angle plays an important role in activating the associated membrane-integrated components of the channel or transporter. Here we report the structure of the C-terminal, KTN-bearing domain of the E. coli KefC K+ efflux system in association with the ancillary subunit, KefF, which is known to stabilize the conductive state. The structure of the complex and functional analysis of KefC variants reveal that control of the conformational flexibility inherent in the KTN dimer hinge is modulated by KefF and essential for regulation of KefC ion flux.
authors.affiliation: Drug Development Department, Nevada Cancer Institute, Las Vegas, NV 89135, USA.
authors.forename: Tarmo P
authors.initials: TP
authors.lastname: Roosild
authors.forename: Samantha
authors.initials: S
authors.lastname: Castronovo
authors.forename: Samantha
authors.initials: S
authors.lastname: Miller
authors.forename: Chan
authors.initials: C
authors.lastname: Li
authors.forename: Tim
authors.initials: T
authors.lastname: Rasmussen
authors.forename: Wendy
authors.initials: W
authors.lastname: Bartlett
authors.forename: Banuri
authors.initials: B
authors.lastname: Gunasekera
authors.forename: Senyon
authors.initials: S
authors.lastname: Choe
authors.forename: Ian R
authors.initials: IR
authors.lastname: Booth
mesh_terms: D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D001665:Binding Sites; D002462:Cell Membrane / Q000378:metabolism*; D017124:Conserved Sequence; D019281:Dimerization; D029968:Escherichia coli Proteins / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism; D019077:Helix-Turn-Helix Motifs; D057927:Hydrophobic and Hydrophilic Interactions; D026901:Membrane Transport Proteins / Q000378:metabolism*; D008969:Molecular Sequence Data; D009154:Mutation; D015221:Potassium Channels / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism; D024661:Potassium Channels, Inwardly Rectifying / Q000737:chemistry* / Q000378:metabolism*; D011485:Protein Binding; D011487:Protein Conformation; D017434:Protein Structure, Tertiary; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D017386:Sequence Homology, Amino Acid
chemical_list: D029968:Escherichia coli Proteins; D026901:Membrane Transport Proteins; D015221:Potassium Channels; D024661:Potassium Channels, Inwardly Rectifying; D011993:Recombinant Fusion Proteins; C069287:KefC protein, E coli