Although the basic facts about the ribosome were already known 40 years ago, elucidating its atomic structure and molecular mechanisms required sheer persistence and the innovative use of new ...technology and methods. These advances have transformed our understanding of translation in the cell.
The publication of crystal structures of the 50S and 30S ribosomal subunits and the intact 70S ribosome is revolutionizing our understanding of protein synthesis. This review is an attempt to ...correlate the structures with biochemical and genetic data to identify the gaps and limits in our current knowledge of the mechanisms involved in translation.
The high-resolution structures of ribosomal subunits published in 2000 have revolutionized the field of protein translation. They facilitated the determination and interpretation of functional ...complexes of the ribosome by crystallography and electron microscopy. Knowledge of the precise positions of residues in the ribosome in various states has facilitated increasingly sophisticated biochemical and genetic experiments, as well as the use of new methods such as single-molecule kinetics. In this review, we discuss how the interaction between structural and functional studies over the last decade has led to a deeper understanding of the complex mechanisms underlying translation.
The structure of the yeast mitochondrial ribosome Desai, Nirupa; Brown, Alan; Amunts, Alexey ...
Science (American Association for the Advancement of Science),
02/2017, Volume:
355, Issue:
6324
Journal Article
Peer reviewed
Open access
Mitochondria have specialized ribosomes (mitoribosomes) dedicated to the expression of the genetic information encoded by their genomes. Here, using electron cryomicroscopy, we have determined the ...structure of the 75-component yeast mitoribosome to an overall resolution of 3.3 angstroms. The mitoribosomal small subunit has been built de novo and includes 15S ribosomal RNA (rRNA) and 34 proteins, including 14 without homologs in the evolutionarily related bacterial ribosome. Yeast-specific rRNA and protein elements, including the acquisition of a putatively active enzyme, give the mitoribosome a distinct architecture compared to the mammalian mitoribosome. At an expanded messenger RNA channel exit, there is a binding platform for translational activators that regulate translation in yeast but not mammalian mitochondria. The structure provides insights into the evolution and species-specific specialization of mitochondrial translation.
The sequential addition of amino acids to a growing polypeptide chain is carried out by the ribosome in a complicated multistep process called the elongation cycle. It involves accurate selection of ...each aminoacyl tRNA as dictated by the mRNA codon, catalysis of peptide bond formation, and movement of the tRNAs and mRNA through the ribosome. The process requires the GTPase factors elongation factor Tu (EF-Tu) and EF-G. Not surprisingly, large conformational changes in both the ribosome and its tRNA substrates occur throughout protein elongation. Major advances in our understanding of the elongation cycle have been made in the past few years as a result of high-resolution crystal structures that capture various states of the process, as well as biochemical and computational studies.
One of the responses to stress by eukaryotic cells is the down-regulation of protein synthesis by phosphorylation of translation initiation factor eIF2. Phosphorylation results in low availability of ...the eIF2 ternary complex (eIF2-GTP-tRNAi) by affecting the interaction of eIF2 with its GTP-GDP exchange factor eIF2B. We have determined the cryo-EM structure of yeast eIF2B in complex with phosphorylated eIF2 at an overall resolution of 4.2 Å. Two eIF2 molecules bind opposite sides of an eIF2B hetero-decamer through eIF2α-D1, which contains the phosphorylated Ser51. eIF2α-D1 is mainly inserted between the N-terminal helix bundle domains of δ and α subunits of eIF2B. Phosphorylation of Ser51 enhances binding to eIF2B through direct interactions of phosphate groups with residues in eIF2Bα and indirectly by inducing contacts of eIF2α helix 58-63 with eIF2Bδ leading to a competition with Met-tRNA
.
The human mitochondrial ribosome (mitoribosome) and associated proteins regulate the synthesis of 13 essential subunits of the oxidative phosphorylation complexes. We report the discovery of a ...mitoribosome-associated quality control pathway that responds to interruptions during elongation, and we present structures at 3.1- to 3.3-angstrom resolution of mitoribosomal large subunits trapped during ribosome rescue. Release factor homolog C12orf65 (mtRF-R) and RNA binding protein C6orf203 (MTRES1) eject the nascent chain and peptidyl transfer RNA (tRNA), respectively, from stalled ribosomes. Recruitment of mitoribosome biogenesis factors to these quality control intermediates suggests additional roles for these factors during mitoribosome rescue. We also report related cryo-electron microscopy structures (3.7 to 4.4 angstrom resolution) of elongating mitoribosomes bound to tRNAs, nascent polypeptides, the guanosine triphosphatase elongation factors mtEF-Tu and mtEF-G1, and the Oxa1L translocase.
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