title: Functional equilibrium of the KcsA structure revealed by NMR.
abstract: KcsA is a tetrameric K(+) channel that is activated by acidic pH. Under open conditions of the helix bundle crossing, the selectivity filter undergoes an equilibrium between permeable and impermeable conformations. Here we report that the population of the permeable conformation (p(perm)) positively correlates with the tetrameric stability and that the population in reconstituted high density lipoprotein, where KcsA is surrounded by the lipid bilayer, is lower than that in detergent micelles, indicating that dynamic properties of KcsA are different in these two media. Perturbation of the membrane environment by the addition of 1-3% 2,2,2-trifluoroethanol increases p(perm) and the open probability, revealed by NMR and single-channel recording analyses. These results demonstrate that KcsA inactivation is determined not only by the protein itself but also by the surrounding membrane environments.
authors.affiliation: Graduate School of Pharmaceutical Sciences, The University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113-0033, Japan.
authors.forename: Shunsuke
authors.initials: S
authors.lastname: Imai
authors.forename: Masanori
authors.initials: M
authors.lastname: Osawa
authors.forename: Kenichiro
authors.initials: K
authors.lastname: Mita
authors.forename: Shou
authors.initials: S
authors.lastname: Toyonaga
authors.forename: Asako
authors.initials: A
authors.lastname: Machiyama
authors.forename: Takumi
authors.initials: T
authors.lastname: Ueda
authors.forename: Koh
authors.initials: K
authors.lastname: Takeuchi
authors.forename: Shigetoshi
authors.initials: S
authors.lastname: Oiki
authors.forename: Ichio
authors.initials: I
authors.lastname: Shimada
mesh_terms: D001426:Bacterial Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D003902:Detergents / Q000737:chemistry; D006863:Hydrogen-Ion Concentration; D008823:Micelles; D019906:Nuclear Magnetic Resonance, Biomolecular; D015221:Potassium Channels / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D017434:Protein Structure, Tertiary; D048170:Streptomyces lividans / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; D003902:Detergents; D008823:Micelles; D015221:Potassium Channels; C107790:prokaryotic potassium channel