title: The open gate structure of the membrane-embedded KcsA potassium channel viewed from the cytoplasmic side.
abstract: Crystallographic studies of channel proteins have provided insight into the molecular mechanisms of ion channels, even though these structures are obtained in the absence of the membrane and some structural portions have remained unsolved. Here we report the gating structure of the membrane-embedded KcsA potassium channel using atomic force microscopy (AFM). The activation gate of the KcsA channel is located on the intracellular side, and the cytoplasmic domain was truncated to clear the view of this location. Once opened, the individual subunits in the tetramer were resolved with the pore open at the center. Furthermore, AFM was able to capture the previously unsolved bulge helix at the entrance. A molecular dynamics simulation revealed that the bulge helices fluctuated dramatically at the open entryway. This dynamic behavior was observed as vigorous open-channel noise in the single-channel current recordings. The role of the bulge helices in the open gate structure is discussed.
authors: Department of Frontier Materials, Graduate School of Engineering, Nagoya Institute of Technology, Nagoya, Japan.
authors: Ayumi
authors: A
authors: Sumino
authors: Takashi
authors: T
authors: Sumikama
authors: Masayuki
authors: M
authors: Iwamoto
authors: Takehisa
authors: T
authors: Dewa
authors: Shigetoshi
authors: S
authors: Oiki
mesh_terms: D001426:Bacterial Proteins / Q000737:chemistry* / Q000378:metabolism; D003593:Cytoplasm / Q000378:metabolism*; D015640:Ion Channel Gating; D018625:Microscopy, Atomic Force; D056004:Molecular Dynamics Simulation; D015221:Potassium Channels / Q000737:chemistry* / Q000378:metabolism; D017434:Protein Structure, Tertiary; D048170:Streptomyces lividans / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; D015221:Potassium Channels