Stabilization of Ribosomal RNA of the Small Subunit by Spermidine in Staphylococcus aureus .
Belinite, M., Khusainov, I., Soufari, H., Marzi, S., Romby, P., Yusupov, M., Hashem, Y.(2021) Front Mol Biosci 8: 738752-738752
- PubMed: 34869582 
- DOI: https://doi.org/10.3389/fmolb.2021.738752
- Primary Citation of Related Structures:  
7KWG - PubMed Abstract: 
Cryo-electron microscopy is now used as a method of choice in structural biology for studying protein synthesis, a process mediated by the ribosome machinery. In order to achieve high-resolution structures using this approach, one needs to obtain homogeneous and stable samples, which requires optimization of ribosome purification in a species-dependent manner. This is especially critical for the bacterial small ribosomal subunit that tends to be unstable in the absence of ligands. Here, we report a protocol for purification of stable 30 S from the Gram-positive bacterium Staphylococcus aureus and its cryo-EM structures: in presence of spermidine at a resolution ranging between 3.4 and 3.6 Å and in its absence at 5.3 Å. Using biochemical characterization and cryo-EM, we demonstrate the importance of spermidine for stabilization of the 30 S via preserving favorable conformation of the helix 44.
Organizational Affiliation: 
Institut de Génétique et de Biologie Moléculaire et Cellulaire (IGBMC), INSERM U964, CNRS UMR7104, Université de Strasbourg, Illkirch, France.