The highly conserved eukaryotic Elongator complex performs specific chemical modifications on wobble base uridines of tRNAs, which are essential for proteome stability and homeostasis. The complex is formed by six individual subunits (Elp1‐6) that are all equally important for its tRNA modification activity. However, its overall architecture and the detailed reaction mechanism remain elusive. Here, we report the structures of the fully assembled yeast Elongator and the Elp123 sub‐complex solved by an integrative structure determination approach showing that two copies of the Elp1, Elp2, and Elp3 subunits form a two‐lobed scaffold, which binds Elp456 asymmetrically. Our topological models are consistent with previous studies on individual subunits and further validated by complementary biochemical analyses. Our study provides a structural framework on how the tRNA modification activity is carried out by Elongator.

The highly conserved Elongator complex modifies transfer RNAs (tRNAs) in their wobble base position, thereby regulating protein synthesis and ensuring proteome stability. The precise mechanisms of tRNA recognition and its modification reaction remain elusive. Here, we show cryo–electron microscopy structures of the catalytic subcomplex of Elongator and its tRNA-bound state at resolutions of 3.3 and 4.4 Å. The structures resolve details of the catalytic site, including the substrate tRNA, the iron-sulfur cluster, and a SAM molecule, which are all validated by mutational analyses in vitro and in vivo. tRNA binding induces conformational rearrangements, which precisely position the targeted anticodon base in the active site. Our results provide the molecular basis for substrate recognition of Elongator, essential to understand its cellular function and role in neurodegenerative diseases and cancer.

Background:The complex formed by the terminase and the connector provides the structural framework and the chemical energy for DNA packaging during bacteriophage morphogenesis. Results: The terminase builds a pentamer that presents two conformational topologies. Conclusion:The conformational change of the terminase might be coupled to DNA packaging. Significance: Terminase function might be based on concerted intersubunit movement within the connector-terminase complex.

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Edited by Wilhelm JustNucleoside modifications in tRNA anticodons regulate ribosome dynamics during translation elongation and, thereby, fine-tune global protein synthesis rates. The highly conserved eukaryotic Elongator complex conducts specific C5-substitutions in tRNA wobble base uridines. It harbors two copies of each of its six individual subunits, which are all equally important for its activity. Here, we summarize recent developments focusing on the architecture of the Elongator complex, showing an asymmetric subunit arrangement, and its functional implications. In addition, we discuss the role of its proposed active site, its individual subunits and temporarily associated regulatory factors. Finally, we aim to provide mechanistic explanations for the link between mutations in Elongator subunits and the onset of several severe human pathologies.