title: Two-dimensional crystallization and projection structure of KcsA potassium channel.
abstract: Potassium channels are integral membrane proteins that play a crucial role in regulating diverse cell functions in both electrically excitable and non-excitable cells. Molecular cloning has revealed a diverse family of genes that encode these proteins, and a variety of experimental strategies have defined functional domains. We have cloned, over-expressed and purified the KcsA potassium channel to homogeneity and reconstituted this channel protein with phospholipids to form two-dimensional crystals. The crystals belong to plane group p4 and have unit cell dimensions of a=b=48 A. A projection map at 6 A resolution has been obtained by electron crystallography. The map shows that the protein is a homotetramer, having a low-density region on the 4-fold axis that is the site of the ion conduction pathway. Each monomer contains density features that are consistent with the molecular model of a truncated form of KcsA recently determined by X-ray crystallography.
authors.affiliation: Lawrence Berkeley National Laboratory, University of California, Berkeley, CA 94720, USA.
authors.forename: H L
authors.initials: HL
authors.lastname: Li
authors.forename: H X
authors.initials: HX
authors.lastname: Sui
authors.forename: S
authors.initials: S
authors.lastname: Ghanshani
authors.forename: S
authors.initials: S
authors.lastname: Lee
authors.forename: P J
authors.initials: PJ
authors.lastname: Walian
authors.forename: C L
authors.initials: CL
authors.lastname: Wu
authors.forename: K G
authors.initials: KG
authors.lastname: Chandy
authors.forename: B K
authors.initials: BK
authors.lastname: Jap
mesh_terms: D001426:Bacterial Proteins / Q000096:biosynthesis / Q000737:chemistry* / Q000235:genetics; D003460:Crystallization; D018360:Crystallography, X-Ray; D019281:Dimerization; D007091:Image Processing, Computer-Assisted; D008565:Membrane Proteins / Q000096:biosynthesis / Q000737:chemistry / Q000235:genetics; D015221:Potassium Channels / Q000096:biosynthesis / Q000737:chemistry* / Q000235:genetics; D011487:Protein Conformation; D013302:Streptomyces
chemical_list: D001426:Bacterial Proteins; D008565:Membrane Proteins; D015221:Potassium Channels; C107790:prokaryotic potassium channel