Structures of B. subtilis Maturation RNases Captured on 50S Ribosome with Pre-rRNAs.
Oerum, S., Dendooven, T., Catala, M., Gilet, L., Degut, C., Trinquier, A., Bourguet, M., Barraud, P., Cianferani, S., Luisi, B.F., Condon, C., Tisne, C.(2020) Mol Cell 80: 227
- PubMed: 32991829 
- DOI: https://doi.org/10.1016/j.molcel.2020.09.008
- Primary Citation of Related Structures:  
6TG6, 6TGJ, 6TNN, 6TPQ - PubMed Abstract: 
The pathways for ribosomal RNA (rRNA) maturation diverge greatly among the domains of life. In the Gram-positive model bacterium, Bacillus subtilis, the final maturation steps of the two large ribosomal subunit (50S) rRNAs, 23S and 5S pre-rRNAs, are catalyzed by the double-strand specific ribonucleases (RNases) Mini-RNase III and RNase M5, respectively. Here we present a protocol that allowed us to solve the 3.0 and 3.1 Å resolution cryoelectron microscopy structures of these RNases poised to cleave their pre-rRNA substrates within the B. subtilis 50S particle. These data provide the first structural insights into rRNA maturation in bacteria by revealing how these RNases recognize and process double-stranded pre-rRNA. Our structures further uncover how specific ribosomal proteins act as chaperones to correctly fold the pre-rRNA substrates and, for Mini-III, anchor the RNase to the ribosome. These r-proteins thereby serve a quality-control function in the process from accurate ribosome assembly to rRNA processing.
Organizational Affiliation: 
Expression Génétique Microbienne, UMR 8261, CNRS, Université de Paris, Institut de Biologie Physico-Chimique (IBPC), 75005 Paris, France.