title: The Intersubunit Bridge B1b of the Bacterial Ribosome Facilitates Initiation of Protein Synthesis and Maintenance of Translational Fidelity.
abstract: In bacteria, ribosomal subunits are connected via 12 intersubunit bridges involving RNA-RNA, RNA-protein, and protein-protein interactions. The only protein-protein bridge in the ribosome is ribosomal intersubunit bridge 1b (B1b), which is mainly formed by the bacterial protein L31 (bL31) and connects the head domain of 30S subunit and the central protuberance of the 50S subunit. It is known to be the most dynamic intersubunit bridge. Here, we have evaluated the role of bL31 and thereby the bridge B1b in the working cycle of the ribosome. First, bL31-deficient ribosomes are severely compromised in their ability to ensure translational fidelity particularly in reading frame maintenance in vivo. Second, in the absence of bL31, the rate of initiation is significantly reduced both in vivo and in vitro. Third, polysome profile and subunit reassociation assays demonstrate that bL31 is important for stabilizing subunit joining in vivo and in vitro. Together, our results demonstrate that bL31 is important for determining translational fidelity and stabilizing subunit association. We conclude that the only protein-protein intersubunit bridge of the bacterial ribosome facilitates translation initiation and is essential for maintaining the reading frame of mRNA translation.
authors.affiliation: Institute of Molecular and Cell Biology, University of Tartu, Riia street 23B, Tartu 51010, Estonia.
authors.forename: Silva
authors.initials: S
authors.lastname: Lilleorg
authors.affiliation: Institute of Molecular and Cell Biology, University of Tartu, Riia street 23B, Tartu 51010, Estonia.
authors.forename: Kaspar
authors.initials: K
authors.lastname: Reier
authors.affiliation: Institute of Molecular and Cell Biology, University of Tartu, Riia street 23B, Tartu 51010, Estonia.
authors.forename: Jaanus
authors.initials: J
authors.lastname: Remme
authors.affiliation: Institute of Molecular and Cell Biology, University of Tartu, Riia street 23B, Tartu 51010, Estonia. Electronic address: aliiv@ut.ee.
authors.forename: Aivar
authors.initials: A
authors.lastname: Liiv
mesh_terms: D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism*; D055786:Gene Knockout Techniques; D010442:Peptide Chain Initiation, Translational; D012269:Ribosomal Proteins / Q000235:genetics / Q000378:metabolism*; D054657:Ribosome Subunits / Q000378:metabolism*
chemical_list: D012269:Ribosomal Proteins; C050985:ribosomal protein L31
keywords: Escherichia coli; bL31; ribosomal proteins; ribosome subunit association; translational fidelity