Poster abstracts
Poster number 25 submitted by Zakkary McNutt
Occlusion of the Anti-Shine-Dalgarno in the Bacteroidetes ribosome
Zakkary A. McNutt (Department of Microbiology & Center for RNA Biology & The Ohio State Biochemistry Program, The Ohio State University, Columbus, Ohio 43210, USA), Bappaditya Roy, Bethany L. Boleratz, Dean E. Watkins, Kurt Fredrick (Department of Microbiology & Center for RNA Biology, The Ohio State University, Columbus, Ohio 43210, USA), Vikash Jha, Dushyant Jahagirdar, Kaustuv Basu, Joaquin Ortega (Department of Anatomy and Cell Biology & Centre for Structural Biology, McGill University, Montreal, Quebec H3G 0B1, Canada), Elan A. Shatoff, Ralf Bundschuh (Department of Physics & Center for RNA Biology, The Ohio State University, Columbus, Ohio 43210, USA)
Abstract:
Genomic studies have indicated that certain bacterial lineages such as the Bacteroidetes lack Shine-Dalgarno (SD) sequences, and yet with few exceptions ribosomes of these organisms carry the conserved anti-SD (ASD) sequence. Here, we show that ribosomes purified from Flavobacterium johnsoniae, a representative of the Bacteroidetes, fail to recognize the SD sequence of mRNA in vitro. A cryo-electron microscopy structure of the complete 70S ribosome from F. johnsoniae at 2.8 Å resolution reveals that the ASD is sequestered by ribosomal proteins bS21, bS18 and bS6, explaining the basis of ASD inhibition. The structure also uncovers a novel ribosomal protein, bL38. Remarkably, in F. johnsoniae and many other Flavobacteriia, the gene encoding bS21 contains a strong SD, unlike virtually all other genes. In those Flavobacteriia that have an alternative ASD, the fully complementary sequence lies upstream of the bS21 gene in all cases, indicative of natural covariation. In the other Bacteroidetes classes, strong SDs are frequently found upstream of the genes for bS21 and/or bS18. We propose that these SDs are used as regulatory elements, enabling bS21 and bS18 to translationally control their own production.
Keywords: Translation , Shine Dalgarno, Bacteroidetes