title: Crystal structure of a translation termination complex formed with release factor RF2.
abstract: We report the crystal structure of a translation termination complex formed by the Thermus thermophilus 70S ribosome bound with release factor RF2, in response to a UAA stop codon, solved at 3 A resolution. The backbone of helix alpha5 and the side chain of serine of the conserved SPF motif of RF2 recognize U1 and A2 of the stop codon, respectively. A3 is unstacked from the first 2 bases, contacting Thr-216 and Val-203 of RF2 and stacking on G530 of 16S rRNA. The structure of the RF2 complex supports our previous proposal that conformational changes in the ribosome in response to recognition of the stop codon stabilize rearrangement of the switch loop of the release factor, resulting in docking of the universally conserved GGQ motif in the PTC of the 50S subunit. As seen for the RF1 complex, the main-chain amide nitrogen of glutamine in the GGQ motif is positioned to contribute directly to catalysis of peptidyl-tRNA hydrolysis, consistent with mutational studies, which show that most side-chain substitutions of the conserved glutamine have little effect. We show that when the H-bonding capability of the main-chain N-H of the conserved glutamine is eliminated by substitution with proline, peptidyl-tRNA esterase activity is abolished, consistent with its proposed role in catalysis.
authors.affiliation: Center for Molecular Biology of RNA and Departments of Molecular, Cell and Developmental Biology and Chemistry and Biochemistry, University of California, Santa Cruz, CA 95064, USA.
authors.forename: Andrei
authors.initials: A
authors.lastname: Korostelev
authors.forename: Haruichi
authors.initials: H
authors.lastname: Asahara
authors.forename: Laura
authors.initials: L
authors.lastname: Lancaster
authors.forename: Martin
authors.initials: M
authors.lastname: Laurberg
authors.forename: Alexander
authors.initials: A
authors.lastname: Hirschi
authors.forename: Jianyu
authors.initials: J
authors.lastname: Zhu
authors.forename: Sergei
authors.initials: S
authors.lastname: Trakhanov
authors.forename: William G
authors.initials: WG
authors.lastname: Scott
authors.forename: Harry F
authors.initials: HF
authors.lastname: Noller
mesh_terms: D000595:Amino Acid Sequence; D018388:Codon, Terminator; D018360:Crystallography, X-Ray; D005973:Glutamine / Q000737:chemistry; D005998:Glycine / Q000737:chemistry; D006860:Hydrogen Bonding; D006868:Hydrolysis; D010454:Peptide Termination Factors / Q000737:chemistry*; D010458:Peptidyl Transferases / Q000737:chemistry; D017433:Protein Structure, Secondary; D012336:RNA, Ribosomal, 16S / Q000737:chemistry; D012343:RNA, Transfer / Q000737:chemistry; D054681:Ribosome Subunits, Large, Bacterial / Q000737:chemistry*; D016963:Thermus thermophilus / Q000378:metabolism*
chemical_list: D018388:Codon, Terminator; D010454:Peptide Termination Factors; D012336:RNA, Ribosomal, 16S; C041460:peptide chain termination release factor 2; D005973:Glutamine; D012343:RNA, Transfer; D010458:Peptidyl Transferases; D005998:Glycine