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After peptide release by a class-1 release factor, the ribosomal subunits must be recycled back to initiation. We have demonstrated that the distance between a strong Shine-Dalgarno (SD) sequence and a codon in the P site is crucial for the binding stability of the deacylated tRNA in the P site of the posttermination ribosome and the in-frame maintenance of its mRNA. We show that the elongation factor EF-G and the ribosomal recycling factor RRF split the ribosome into subunits in the absence of initiation factor 3 (IF3) by a mechanism that requires both GTP and GTP hydrolysis. Taking into account that EF-G in the GTP form and RRF bind with positive cooperativity to the free 50S subunit but with negative cooperativity to the 70S ribosome, we suggest a mechanism for ribosome recycling that specifies distinct roles for EF-G, RRF, and IF3.
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http://dx.doi.org/10.1016/j.molcel.2005.05.016 | DOI Listing |
Sci Adv
May 2025
Department of Biochemistry, Gene Center, Feodor-Lynen-Str. 25, University of Munich, 81377, Munich, Germany.
Degradation of arrest peptides from endoplasmic reticulum (ER) translocon-bound 60 ribosomal subunits via the ribosome-associated quality control (ER-RQC) pathway requires covalent modification of RPL26/uL24 on 60 ribosomal subunits with UFM1. However, the underlying mechanism that coordinates the UFMylation and RQC pathways remains elusive. Structural analysis of ER-RQC intermediates revealed concomitant binding and direct interaction of the UFMylation and RQC machineries on the 60.
View Article and Find Full Text PDFNature
March 2024
Department of Biology, Stanford University, Stanford, CA, USA.
Reversible modification of target proteins by ubiquitin and ubiquitin-like proteins (UBLs) is widely used by eukaryotic cells to control protein fate and cell behaviour. UFM1 is a UBL that predominantly modifies a single lysine residue on a single ribosomal protein, uL24 (also called RPL26), on ribosomes at the cytoplasmic surface of the endoplasmic reticulum (ER). UFM1 conjugation (UFMylation) facilitates the rescue of 60S ribosomal subunits (60S) that are released after ribosome-associated quality-control-mediated splitting of ribosomes that stall during co-translational translocation of secretory proteins into the ER.
View Article and Find Full Text PDFG3 (Bethesda)
March 2024
Department of Molecular Biology and Genetics, Howard Hughes Medical Institute, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA.
The decay of messenger RNA with a premature termination codon by nonsense-mediated decay (NMD) is an important regulatory pathway for eukaryotes and an essential pathway in mammals. NMD is typically triggered by the ribosome terminating at a stop codon that is aberrantly distant from the poly-A tail. Here, we use a fluorescence screen to identify factors involved in NMD in Saccharomyces cerevisiae.
View Article and Find Full Text PDFFront Microbiol
November 2023
Institute for Molecular Biosciences, Biocentre, Goethe-University, Frankfurt, Germany.
Genomes of bacteria and archaea contain a much larger fraction of unidirectional (serial) gene pairs than convergent or divergent gene pairs. Many of the unidirectional gene pairs have short overlaps of -4 nt and -1 nt. As shown previously, translation of the genes in overlapping unidirectional gene pairs is tightly coupled.
View Article and Find Full Text PDFNucleic Acids Res
June 2023
Department of Structural Biology, Stanford University School of Medicine, Stanford, CA 94305-5126, USA.
In bacteria, release of newly synthesized proteins from ribosomes during translation termination is catalyzed by class-I release factors (RFs) RF1 or RF2, reading UAA and UAG or UAA and UGA codons, respectively. Class-I RFs are recycled from the post-termination ribosome by a class-II RF, the GTPase RF3, which accelerates ribosome intersubunit rotation and class-I RF dissociation. How conformational states of the ribosome are coupled to the binding and dissociation of the RFs remains unclear and the importance of ribosome-catalyzed guanine nucleotide exchange on RF3 for RF3 recycling in vivo has been disputed.
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