title: The non-selective cation-permeable channel TRPC3 is a tetrahedron with a cap on the large cytoplasmic end.
abstract: TRPC3 plays important roles in neuronal differentiation and immune cell maturation by mediating the cationic current in response to phospholipase C activation, Ca2+ depletion, and diacylglycerol stimulation. Here, we purified the TRPC3 channel using a glycosylated tetramer and observed the structure using electron microscopy. Negatively stained specimens demonstrate homogeneous protein particles containing an internal cavity-like structure. These particle images were picked up by automated pick-up programs, aligned, and classified by the growing neural gas network method. Similarly oriented projections were averaged to decrease the signal-to-noise ratio. The averaged images progress from the top view to the side views, which are representative of their raw images. The top view confirmed the hypothesis of a four-domain structure, and the side view demonstrates a large cytoplasmic domain with a capped structure at the bottom, which is near a predicted locus of ion release. The total image of the protein is a blunt-edged trapezoid of 200 x 200 x 235 A. This large dimension of TRPC3 is also supported by the Stokes radius (92 A) obtained from gel filtration chromatography.
authors.affiliation: Neuroscience Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), Umezono 1-1-4, Tsukuba, Ibaraki 305-8568, Japan.
authors.forename: Kazuhiro
authors.initials: K
authors.lastname: Mio
authors.forename: Toshihiko
authors.initials: T
authors.lastname: Ogura
authors.forename: Yuji
authors.initials: Y
authors.lastname: Hara
authors.forename: Yasuo
authors.initials: Y
authors.lastname: Mori
authors.forename: Chikara
authors.initials: C
authors.lastname: Sato
mesh_terms: D002850:Chromatography, Gel; D003593:Cytoplasm / Q000378:metabolism*; D004591:Electrophoresis, Polyacrylamide Gel; D007473:Ion Channels / Q000737:chemistry / Q000378:metabolism*; D008854:Microscopy, Electron; D008958:Models, Molecular; D050052:TRPC Cation Channels
chemical_list: D007473:Ion Channels; D050052:TRPC Cation Channels; C104603:TRPC3 cation channel