title: Three-dimensional structure of a pre-catalytic human spliceosomal complex B.
abstract: Major structural changes occur in the spliceosome during its transition from the fully assembled complex B to the catalytically activated spliceosome. To understand the rearrangement, it is necessary to know the detailed three-dimensional structures of these complexes. Here, we have immunoaffinity-purified human spliceosomes (designated B Delta U1) at a stage after U4/U6.U5 tri-snRNP integration but before activation, and have determined the three-dimensional structure of B Delta U1 by single-particle electron cryomicroscopy at a resolution of approximately 40 A. The overall size of the complex is about 370 x 270 x 170 A. The three-dimensional structure features a roughly triangular body linked to a head domain in variable orientations. The body is very similar in size and shape to the isolated U4/U6.U5 tri-snRNP. This provides initial insight into the structural organization of complex B.
authors.affiliation: Max Planck Institute for Biophysical Chemistry, Department of Cellular Biochemistry, Am Fassberg 11, 37077 Goettingen, Germany.
authors.forename: Daniel
authors.initials: D
authors.lastname: Boehringer
authors.forename: Evgeny M
authors.initials: EM
authors.lastname: Makarov
authors.forename: Bjoern
authors.initials: B
authors.lastname: Sander
authors.forename: Olga V
authors.initials: OV
authors.lastname: Makarova
authors.forename: Berthold
authors.initials: B
authors.lastname: Kastner
authors.forename: Reinhard
authors.initials: R
authors.lastname: Lührmann
authors.forename: Holger
authors.initials: H
authors.lastname: Stark
mesh_terms: D002384:Catalysis; D006801:Humans; D008854:Microscopy, Electron; D011487:Protein Conformation; D011506:Proteins / Q000737:chemistry* / Q000648:ultrastructure; D017381:Spliceosomes / Q000737:chemistry* / Q000648:ultrastructure
chemical_list: D011506:Proteins