title: A 9 A resolution X-ray crystallographic map of the large ribosomal subunit.
abstract: The 50S subunit of the ribosome catalyzes the peptidyl-transferase reaction of protein synthesis. We have generated X-ray crystallographic electron density maps of the large ribosomal subunit from Haloarcula marismortui at various resolutions up to 9 A using data from crystals that diffract to 3 A. Positioning a 20 A resolution EM image of these particles in the crystal lattice produced phases accurate enough to locate the bound heavy atoms in three derivatives using difference Fourier maps, thus demonstrating the correctness of the EM model and its placement in the unit cell. At 20 A resolution, the X-ray map is similar to the EM map; however, at 9 A it reveals long, continuous, but branched features whose shape, diameter, and right-handed twist are consistent with segments of double-helical RNA that crisscross the subunit.
authors.affiliation: Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, Connecticut 06520-8114, USA.
authors.forename: N
authors.initials: N
authors.lastname: Ban
authors.forename: B
authors.initials: B
authors.lastname: Freeborn
authors.forename: P
authors.initials: P
authors.lastname: Nissen
authors.forename: P
authors.initials: P
authors.lastname: Penczek
authors.forename: R A
authors.initials: RA
authors.lastname: Grassucci
authors.forename: R
authors.initials: R
authors.lastname: Sweet
authors.forename: J
authors.initials: J
authors.lastname: Frank
authors.forename: P B
authors.initials: PB
authors.lastname: Moore
authors.forename: T A
authors.initials: TA
authors.lastname: Steitz
mesh_terms: D018360:Crystallography, X-Ray / Q000379:methods*; D019614:Haloarcula marismortui / Q000737:chemistry*; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D008854:Microscopy, Electron / Q000379:methods; D019642:RNA, Archaeal / Q000737:chemistry; D012341:RNA, Ribosomal, 5S / Q000737:chemistry; D012269:Ribosomal Proteins / Q000737:chemistry; D012270:Ribosomes / Q000737:chemistry*
chemical_list: D019642:RNA, Archaeal; D012341:RNA, Ribosomal, 5S; D012269:Ribosomal Proteins; C028546:ribosomal protein L1