Poster abstracts
Poster number 27 submitted by Bryan Gemler
Ribosomes Lacking bS21 Gain Function to Regulate Protein Synthesis in Flavobacterium johnsoniae
Bryan T Gemler (Biophysics), Zakkary A McNutt, Bappaditya Roy (Department of Microbiology, The Ohio State University), Elan A Shatoff (Department of Physics, The Ohio State University), Kyung-Mee Moon, Leonard J Foster (Department of Biochemistry and Molecular Biology, Michael Smith Laboratories, University of British Columbia), Ralf Bundschuh (Department of Physics, The Ohio State University), Kurt Fredrick (Department of Microbiology, The Ohio State University)
Abstract:
The Shine Dalgarno (SD) sequence is commonly found in the 5' untranslated region of mRNA and promotes translation initiation in many bacteria. However, ribosomes in species belonging to Bacteroidia (formerly Bacteroidetes) fail to recognize the SD even though their 16S rRNA contains the anti-SD (ASD), a phenomenon explained by the sequestration of the ASD by a pocket formed by the bS21, bS18, and bS6 proteins on the 30S ribosomal subunit. Our research has shown that only a single gene across many Flavobacteriales (an taxonomic order of Bacteroidia) species, rpsU (the gene encoding bS21), contains a strong SD sequence. Experimental evidence demonstrates that bS21 synthesis in Flavobacterium johnsoniae is autoregulated by ribosomes lacking bS21, whose ASD is liberated, allowing it to contact the rpsU SD. Purified ribosomes lacking bS21 exhibit higher initiation rates on rpsU mRNA and lower initiation rates on other (SD-less) mRNAs than control ribosomes. Mutation or deletion of bS21 in the cell increases translation of reporters with strong SD sequences but has no effect on other reporters. Computational evidence supported the proposed autoregulation mechanism by revealing exceptionally strong rpsU SD sequences with predicted SD-ASD pairing free energies of <-13 kcal/mol. Further, a scaleable approach was developed to interrogate the strength of the rpsU SD relative to all other genes coding for ribosomal proteins across a large number of species in the Bacteriodota phylum. As a whole this work provides a clear, unambiguous example of specialized bacterial ribosomes, defined as those with altered composition and function.
References:
McNutt ZA, Roy B, Gemler BT, Shatoff EA, Moon KM, Foster LJ, Bundschuh R, Fredrick K. Ribosomes lacking bS21 gain function to regulate protein synthesis in Flavobacterium johnsoniae. Nucleic Acids Res. 2023 Feb 28;51(4):1927-1942. doi: 10.1093/nar/gkad047. PMID: 36727479; PMCID: PMC9976891.
Keywords: translation initation, specialized ribosomes, autoregulation mechanism