title: Three-dimensional model of yeast RNA polymerase I determined by electron microscopy of two-dimensional crystals.
abstract: Two-dimensional crystals of yeast RNA polymerase I dimers were obtained upon interaction with positively charged lipid layers. A three-dimensional surface model of the enzyme was determined by analyzing tilted crystalline areas and by taking advantage of the non-crystallographic internal symmetry of the dimer to correct for the missing viewing directions. The structure shows, at approximately 3 nm resolution, an irregularly shaped molecule 11 nm x 11 nm x 15 nm in size characterized by a 3 nm wide and 10 nm long groove which constitutes a putative DNA binding site. The overall structure is similar to the Escherichia coli holo enzyme and the yeast RNA polymerase II delta 4/7 structures. The most remarkable structural feature is a finger-shaped stalk which partially occludes the entrance of the groove and forms a 2.5 nm wide channel. We discuss the possible location of the catalytic centre and of the carboxy-terminal region of the beta-like subunit in the channel. The interference of different DNA fragments with RNA polymerase dimerization and crystallization indicates the orientation of the template in the putative DNA binding groove.
authors.affiliation: Laboratoire de Génétique Moléculaire des Eucaryotes, France.
authors.forename: P
authors.initials: P
authors.lastname: Schultz
authors.forename: H
authors.initials: H
authors.lastname: Célia
authors.forename: M
authors.initials: M
authors.lastname: Riva
authors.forename: A
authors.initials: A
authors.lastname: Sentenac
authors.forename: P
authors.initials: P
authors.lastname: Oudet
mesh_terms: D000595:Amino Acid Sequence; D001483:Base Sequence; D003460:Crystallization; D004247:DNA / Q000378:metabolism; D007091:Image Processing, Computer-Assisted; D008854:Microscopy, Electron; D008958:Models, Molecular; D008969:Molecular Sequence Data; D011485:Protein Binding; D011487:Protein Conformation; D012318:RNA Polymerase I / Q000737:chemistry* / Q000378:metabolism / Q000648:ultrastructure; D012441:Saccharomyces cerevisiae / Q000201:enzymology*; D016415:Sequence Alignment; D013698:Templates, Genetic
chemical_list: D004247:DNA; D012318:RNA Polymerase I