Biology subjects

Wanes, G.

Publications and source records attributed to Wanes, G..

3 recordsLinked to original sources

bioRxiv2026

Ribosomal Protein bL27 Protects Translating Ribosomes from tmRNA-SmpB

Bacterial ribosomal protein bL27 is universally conserved and its amino terminus is adjacent to the peptidyl transfer center, yet its role in translation remains unclear. Combining genetics, biochemistry and molecular dynamics, we show that bL27 has an unexpected role in preventing trans-translation, the bacterial ribosome rescue mechanism, from interfering with protein synthesis. Deletion of the bL27 gene causes a 10,000-fold decrease in viability and this defect is partially rescued by deletion of the gene encoding tmRNA, a critical molecule for trans-translation. Molecular dynamics simulations also indicate that bL27 can slow the movement of tmRNA on the ribosome. These data link trans-translation and bL27, and support a model in which the amino terminus of bL27 acts as a gatekeeper to prevent tmRNA from sterically interfering with tRNA on the ribosome.

biochemistry↗

bioRxiv2025

Transient ion-mediated interactions regulate subunit rotation in a eukaryotic ribosome

While it is known that ions are required for folding of RNA, little is known about how transient/probabilistic ionic interactions facilitate biologically-relevant conformational rearrangements. To address this, we developed a theoretical model that employs all-atom resolution, with a simplified representation of biomolecular energetics, explicit electrostatics and ions (K+, Cl-, Mg2+). For well-studied RNA systems (58-mer and Ade riboswitch), the model accurately describes the concentration-dependent ionic environment, including (bidentate) chelated and hydrated (diffuse/outer-shell) ions. With this foundation, we applied the model to simulate the yeast ribosome and quantified the ion-dependent energy landscape of intersubunit rotation. These calculations show how the energetics of rotation responds to millimolar changes in [MgCl2], which shift the distribution between rotation states and alter the kinetics by more than an order of magnitude. We find that this response to the ionic concentration correlates with formation and breakage of ion-mediated interactions (inner-shell and outer-shell) between the ribosomal subunits. This analysis provides a physical basis for understanding how transient ion-mediated interactions can regulate a large-scale biological process.

biophysics↗

bioRxiv2025

Mettl15-Mettl17 modulates the transition from early to late pre-mitoribosome

The assembly of the mitoribosomal small subunit involves folding and modification of rRNA, and its association with mitoribosomal proteins. This process is assisted by a dynamic network of assembly factors. Conserved methyltransferases Mettl15 and Mettl17 act on the solvent-exposed surface of rRNA. Binding of Mettl17 is associated with the early assembly stage, whereas Mettl15 is involved in the late stage, but the mechanism of transition between the two was unclear. Here, we integrate structural data from Trypanosoma brucei with mammalian homologs and molecular dynamics simulations. We reveal how the interplay of Mettl15 and Mettl17 in intermediate steps links the distinct stages of small subunit assembly. The analysis suggests a model wherein Mettl17 acts as a platform for Mettl15 recruitment. Subsequent release of Mettl17 allows a conformational change of Mettl15 for substrate recognition. Upon methylation, Mettl15 adopts a loosely bound state which ultimately leads to its replacement by initiation factors, concluding the assembly. Together, our results indicate that assembly factors Mettl15 and Mettl17 cooperate to regulate the biogenesis process, and present a structural data resource for understanding molecular adaptations of assembly factors in mitoribosome.

molecular biology↗