title: Mechanism of Cd2+ coordination during slow inactivation in potassium channels.
abstract: In K+ channels, rearrangements of the pore outer vestibule have been associated with C-type inactivation gating. Paradoxically, the crystal structure of Open/C-type inactivated KcsA suggests these movements to be modest in magnitude. In this study, we show that under physiological conditions, the KcsA outer vestibule undergoes relatively large dynamic rearrangements upon inactivation. External Cd2+ enhances the rate of C-type inactivation in an cysteine mutant (Y82C) via metal-bridge formation. This effect is not present in a non-inactivating mutant (E71A/Y82C). Tandem dimer and tandem tetramer constructs of equivalent cysteine mutants in KcsA and Shaker K+ channels demonstrate that these Cd2+ metal bridges are formed only between adjacent subunits. This is well supported by molecular dynamics simulations. Based on the crystal structure of Cd2+ -bound Y82C-KcsA in the closed state, together with electron paramagnetic resonance distance measurements in the KcsA outer vestibule, we suggest that subunits must dynamically come in close proximity as the channels undergo inactivation.
authors: Department of Biochemistry and Molecular Biology, The University of Chicago, Chicago, IL, USA.
authors: H
authors: H
authors: Raghuraman
authors: Julio F
authors: JF
authors: Cordero-Morales
authors: Vishwanath
authors: V
authors: Jogini
authors: Albert C
authors: AC
authors: Pan
authors: Astrid
authors: A
authors: Kollewe
authors: Benoît
authors: B
authors: Roux
authors: Eduardo
authors: E
authors: Perozo
mesh_terms: D020816:Amino Acid Motifs; D019943:Amino Acid Substitution; D001426:Bacterial Proteins / Q000737:chemistry* / Q000235:genetics; D002104:Cadmium / Q000737:chemistry*; D056831:Coordination Complexes / Q000737:chemistry*; D018360:Crystallography, X-Ray; D004578:Electron Spin Resonance Spectroscopy; D008081:Liposomes / Q000737:chemistry; D056004:Molecular Dynamics Simulation; D015221:Potassium Channels / Q000737:chemistry* / Q000235:genetics; D055550:Protein Stability; D020836:Protein Structure, Quaternary; D021122:Protein Subunits / Q000737:chemistry; D048170:Streptomyces lividans; D013816:Thermodynamics
chemical_list: D001426:Bacterial Proteins; D056831:Coordination Complexes; D008081:Liposomes; D015221:Potassium Channels; D021122:Protein Subunits; C107790:prokaryotic potassium channel; D002104:Cadmium