biostudies-literatureMcNutt ZANSERCGenome CanadaNational Science Foundation1927-1942https://www.ebi.ac.uk/biostudies/studies/S-EPMC9976891biostudies-literatureUnknown51(4)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 reNucleic acids researchRibosomes lacking bS21 gain function to regulate protein synthesis in Flavobacterium johnsoniae.PMC9976891MCB-2029502264PROShatoff EAMcNutt ZABundschuh RFredrick KRoy BMoon KMFoster LJGemler BTfalseRibosomes lacking bS21 gain function to regulate protein synthesis in Flavobacterium johnsoniae.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 re2023-01-01T00:00:00Z2023 Feb2026-04-08T14:11:01.967Z2024-11-06T04:42:18.258ZS-EPMC99768913672747910.1093/nar/gkad047