Poster abstracts
Poster number 42 submitted by Bappaditya Roy
Ribosomes lacking bS21 gain function to regulate protein synthesis
Bappaditya Roy (Department of Microbiology, Center for RNA Biology, The Ohio State University, Columbus, Ohio 43210, USA), Zakkary A. McNutt (Ohio State Biochemistry Program, Center for RNA Biology, The Ohio State University, Columbus, Ohio 43210, USA), Bryan T. Gemler (Department of Physics, Center for RNA Biology, The Ohio State University, Columbus, Ohio 43210, USA), Elan A. Shatoff (Department of Physics, Center for RNA Biology, The Ohio State University, Columbus, Ohio 43210, USA), Ralf Bundschuh (Department of Physics, Department of Chemistry & Biochemistry, 7Division of Hematology, Department of Internal Medicine, Center for RNA Biology, The Ohio State University, Columbus, Ohio 43210, USA), Kurt Fredrick (Department of Microbiology, Ohio State Biochemistry Program, Center for RNA Biology, The Ohio State University, Columbus, Ohio 43210, USA)
Abstract:
Ribosomes of Bacteroidia (formerly Bacteroidetes) fail to recognize Shine-Dalgarno (SD) sequences even though they harbor the anti-SD (ASD) of 16S rRNA. Inhibition of SD-ASD pairing is due to sequestration of the 3’ tail of 16S rRNA in a pocket formed by bS21, bS18, and bS6 on the 30S platform. Interestingly, in many Flavobacteriales, the gene encoding bS21, rpsU, contains an extended SD sequence. In this work, we present genetic and biochemical evidence that bS21 synthesis in Flavobacterium johnsoniae is autoregulated via a subpopulation of ribosomes that specifically lack bS21. Mutation or depletion of bS21 in the cell increases translation of reporters with strong SD sequences, such as rpsU’-gfp, but has no effect on other reporters. Purified ribosomes lacking bS21 (or its C-terminal region) exhibit higher rates of initiation on rpsU mRNA and lower rates of initiation on other (SD-less) mRNAs than control ribosomes. The mechanism of autoregulation depends on extensive pairing between mRNA and 16S rRNA, and exceptionally strong SD sequences, with predicted pairing free energies of < –13 kcal/mol, are characteristic of rpsU across the Bacteroidota. This work uncovers a clear example of specialized ribosomes in bacteria.
Keywords: ribosome, bS21