title: Placement of protein and RNA structures into a 5 A-resolution map of the 50S ribosomal subunit.
abstract: We have calculated at 5.0 A resolution an electron-density map of the large 50S ribosomal subunit from the bacterium Haloarcula marismortui by using phases derived from four heavy-atom derivatives, intercrystal density averaging and density-modification procedures. More than 300 base pairs of A-form RNA duplex have been fitted into this map, as have regions of non-A-form duplex, single-stranded segments and tetraloops. The long rods of RNA crisscrossing the subunit arise from the stacking of short, separate double helices, not all of which are A-form, and in many places proteins crosslink two or more of these rods. The polypeptide exit channel was marked by tungsten cluster compounds bound in one heavy-atom-derivatized crystal. We have determined the structure of the translation-factor-binding centre by fitting the crystal structures of the ribosomal proteins L6, L11 and L14, the sarcin-ricin loop RNA, and the RNA sequence that binds L11 into the electron density. We can position either elongation factor G or elongation factor Tu complexed with an aminoacylated transfer RNA and GTP onto the factor-binding centre in a manner that is consistent with results from biochemical and electron microscopy studies.
authors.affiliation: Department of Molecular Biophysics & Biochemistry, Yale University, Howard Hughes Medical Institute, New Haven, Connecticut 06520-8114, USA.
authors.forename: N
authors.initials: N
authors.lastname: Ban
authors.forename: P
authors.initials: P
authors.lastname: Nissen
authors.forename: J
authors.initials: J
authors.lastname: Hansen
authors.forename: M
authors.initials: M
authors.lastname: Capel
authors.forename: P B
authors.initials: PB
authors.lastname: Moore
authors.forename: T A
authors.initials: TA
authors.lastname: Steitz
mesh_terms: D019843:Archaeal Proteins / Q000737:chemistry; D018360:Crystallography, X-Ray; D019614:Haloarcula marismortui / Q000737:chemistry / Q000648:ultrastructure; D009690:Nucleic Acid Conformation; D011487:Protein Conformation; D019642:RNA, Archaeal / Q000737:chemistry; D012335:RNA, Ribosomal / Q000737:chemistry*; D012269:Ribosomal Proteins / Q000737:chemistry*; D012270:Ribosomes / Q000737:chemistry* / Q000648:ultrastructure
chemical_list: D019843:Archaeal Proteins; D019642:RNA, Archaeal; D012335:RNA, Ribosomal; D012269:Ribosomal Proteins; C027624:ribosomal protein L11; C041174:ribosomal protein L14; C031249:ribosomal protein L6