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N-Myristoylation by NMT1 is an essential modification in humans safeguarding transient membrane anchorage of proteins. Here, the authors use cryo-EM to visualize the foundation for the co-translational modification activity of NMT1 on the ribosome.

The kinase ZAK is activated at collided ribosomes to mediate the ribotoxic stress response.

Membrane protein topogenesis is not fully understood, although the path that proteins take through the ribosome and Sec-complex has been described. Here, Bischoff et al.present the structure of a ribosome-SecY complex containing an intermediate of proteorhodopsin, which provides further insight into this topogenesis.

Previous studies argued that nascent polypeptide chains can form secondary structure in the ribosome exit tunnel despite spatial constraints. Using single-particle cryo-EM reconstructions of eukaryotic ribosomes carrying nascent chains with high helical propensity, density consistent with helix formation is now observed in the exit tunnel as are interactions with tunnel proteins.

During synthesis, modification and maturation of the ribosomal RNA, correct subdomain folding without additional guidance poses a major challenge. Here, the authors observe the snR30 H/ACA snoRNP forming a “satellite particle” with the 90S, the earliest known pre-ribosome, where localized structural interactions guide its independent folding.

The pathogen Pseudomonas aeruginosa uses a membrane complex, PelBC, to produce exopolysaccharides for biofilm formation. Here the authors combine structural analysis, simulations and single-channel recordings of PelBC to provide a detailed view on its unique architecture and dynamics, and reveal the export route for the polysaccharide.

The cryo-EM structure of the N-terminal acetyl transferase NatA in complex with the ribosome shows that NatA is dynamically positioned underneath the ribosomal exit tunnel to facilitate modification of the emerging nascent peptide chain.

Studies of five cryo-electron microscopy structures reveal the composition and conformational progression in the final maturation events of human 40S ribosomal subunit assembly.

Ribosome collisions serve as proxy for aberrant translation to initiate rescue and quality control pathways. Here, authors elucidate the molecular mechanism of collided ribosome clearance by the ribosome quality control trigger complex.

Assembly of the mitoribosome requires assistance from numerous specialized factors. Here, structures of the human 39S late assembly intermediates identify several assembly factors which keep the 16S rRNA in immature conformations, and reveal deacylated tRNA in the ribosomal E-site, suggesting a role in 39S assembly.

The cryo-EM structure of the Saccharomyces cerevisiae 80S ribosome–Xrn1 nuclease complex reveals how the conserved core of Xrn1 allows binding at the mRNA exit channel of the ribosome, ensuring efficient degradation of mRNA after the final round of translation.

Cryo-EM structures of late intermediates in the assembly of human 40S ribosomal subunits help to define the principles by which immature rRNA conformations and ribosomal biogenesis factors shape the 40S maturation process.

The cryo-EM structure of Bcs1, an AAA-ATPase of the inner mitochondrial membrane, reveals two large aqueous vestibules separated by a seal-forming middle domain, an architecture that suggests an airlock-like translocation mechanism for its folded substrate.

Otu2-driven deubiquitylation of ribosomal protein eS7 impacts translational efficiency. Here, the authors provide the molecular basis for recognition of monoubiquitinated eS7 on 40S and give mechanistic insights into Otu2’s role in translation reset.

Our understanding of ribosome biogenesis is limited by a lack of structural knowledge of assembly intermediates. Here, Leidig et al.report a high-resolution cryo-EM structure of a pre-60S particle that suggests that substantial rearrangements of the 5S RNP are required during ribosome maturation.

In bacteria, the ribosomal stalling during translation of leader peptides is a mechanism of antibiotic resistance that has not been well understood. Here, the structure of a drug-dependent stalled ribosome complex has allowed the authors to propose a detailed mechanism for this translational arrest.

In bacteria, a newly identified endonuclease activated by ribosome collisions truncates mRNA to trigger rescue of stalled ribosomes.

Bacterial responses to nutrient limitation and other stress conditions are often modulated by the nucleotide-based second messenger (p)ppGpp. Here, the authors show that (p)ppGpp inhibits the SRP membrane-protein insertion and secretion pathway by binding to GTPases Ffh and FtsY.

Cryo-EM structures of the yeast 40S in complex with ribosome-splitting protein ABCE1, along with functional analyses, reveal that the FeS cluster domain undergoes a 150° rotation to dissociate ribosomal subunits.

Messenger RNAs (mRNAs) that induce stalling during translation are degraded by a quality control mechanism known as no-go decay (NGD). The aberrant mRNAs are recognized by two factors, Dom34 and Hbs1. Using cryo-EM to visualize NGD intermediates bound to a stalled ribosome, Beckman and coworkers suggest how binding of Dom34-Hbs1 may lead to ribosome disassembly and recruitment of mRNA degradation factors.

High-resolution cryo-EM density maps are used to present the structures of Drosophila and human 80S ribosomes in complex with eEF2, E-site transfer RNA and Stm1-like proteins, and reveal the presence of two additional structural layers in the ribosomes of metazoan eukaryotes.

A cryo-EM structure of the bacterial ribosome–SecYEG complex in a so-called Nanodisc allows for the molecular interpretation of the SecYEG complex in its natural lipid bilayer environment. Molecular dynamics simulations based on the structure reveal stable interactions between ribosomal RNA and the membrane that may contribute to the insertase activity of the protein-conducting channel.

Form I Rubisco, one of the most abundant proteins in nature, catalyses the fixation of atmospheric CO₂ in photosynthesis. The limited catalytic efficiency of Rubisco has sparked extensive efforts to re-engineer the enzyme to enhance agricultural productivity. To bring this goal closer, the formation of cyanobacterial form I Rubisco is now analysed by in vitro reconstitution and cryo-electron microscopy.

Ribosome stalling regulates gene expression by exposing otherwise inaccessible downstream ribosome-binding sites. Here the authors present a high-resolution Cryo-EM structure of the Bacillus subtilisMifM-stalled 70S ribosome to provide mechanistic insight into species-specific nascent peptide induced translational arrest.

Antimicrobial peptide Api137 inhibits translation by trapping release factors 1 or 2 associated with ribosomes and arresting termination.

Cryo-electron-microscopy reconstructions of eukaryotic and archaeal ribosomes bound by ABCE1 and Pelota suggest a conserved mechanism for ribosome recycling.

The cryo-EM structure of a nucleoplasmic pre-60S particle with the Rix1–Rea1 checkpoint machinery reveals insights into pre-60S maturation before nuclear export.

The near-atomic structure of the Chaetomium thermophilum 90S preribosome explains how assembly factors and pre-rRNA guide folding of pre-40S domains and suggests a proofreading model for the 90S–pre-40S transition.

Cryo-electron-microscopy imaging of hibernating ribosomes from Escherichia coli elucidates the molecular composition of these complexes and their mode of assembly, reveals how translation initiation is inhibited, and identifies a role for the ribosomal protein S1 in ribosome inactivation.

Cryo-electron microscopy structures of the yeast 60S ribosomal subunit in complex with Vms1 provides insights into the roles of proteins in the ribosome-associated quality control pathway.

Nascent secretory and membrane proteins are targeted to the Sec61 protein-conducting channel for translocation across or insertion into the endoplasmic reticulum membrane; here cryo-electron microscopy structures of eukaryotic ribosome–channel complexes show how this channel opens vertically during translocation of a secretory protein into the lumen of the endoplasmic reticulum and how it opens laterally during insertion of a transmembrane domain into the lipid bilayer.

The structure of the bacterial ribosome stalled on a truncated mRNA in complex with ArfA and the release factor RF2 is presented, revealing how ArfA recruits RF2 to the ribosome and induces conformational changes within RF2 to enable translation termination in the absence of a stop codon.