RNA Therapeutics Institute Publications


Structural dynamics of protein S1 on the 70S ribosome visualized by ensemble cryo-EM

UMMS Affiliation

RNA Therapeutics Institute; Department of Biochemistry and Molecular Pharmacology

Publication Date


Document Type



Amino Acids, Peptides, and Proteins | Biochemistry, Biophysics, and Structural Biology | Nucleic Acids, Nucleotides, and Nucleosides


Bacterial ribosomal protein S1 is the largest and highly flexible protein of the 30S subunit, and one of a few core ribosomal proteins for which a complete structure is lacking. S1 is thought to participate in transcription and translation. Best understood is the role of S1 in facilitating translation of mRNAs with structured 5' UTRs. Here, we present cryo-EM analyses of the 70S ribosome that reveal multiple conformations of S1. Based on comparison of several 3D maximum likelihood classification approaches in Frealign, we propose a streamlined strategy for visualizing a highly dynamic component of a large macromolecular assembly that itself exhibits high compositional and conformational heterogeneity. The resulting maps show how S1 docks at the ribosomal protein S2 near the mRNA exit channel. The globular OB-fold domains sample a wide area around the mRNA exit channel and interact with mobile tails of proteins S6 and S18. S1 also interacts with the mRNA entrance channel, where an OB-fold domain can be localized near S3 and S5. Our analyses suggest that S1 cooperates with other ribosomal proteins to form a dynamic mesh near the mRNA exit and entrance channels to modulate the binding, folding and movement of mRNA.


3D maximum-likelihood classification, Electron cryo-microscopy, Ribosome, Rps1

DOI of Published Version



Methods. 2018 Mar 15;137:55-66. doi: 10.1016/j.ymeth.2017.12.004. Epub 2017 Dec 14. Link to article on publisher's site

Journal/Book/Conference Title

Methods (San Diego, Calif.)

Related Resources

Link to Article in PubMed

PubMed ID