Poster abstracts
Poster number 4 submitted by Siddik Alom
Protein bL38 facilitates incorporation of uL6 during assembly of the 50S subunit in Flavobacterium johnsoniae
Md. Siddik Alom (1Ohio State Biochemistry Program, 2Center for RNA Biology, The Ohio State University, Columbus, OH 43210, USA), Dominic Arpin, Haojun Zhu (3Department of Anatomy and Cell Biology, McGill University, Montreal, Quebec H3A 0C7, Canada; 4Centre for Structural Biology, McGill University, Montreal, Quebec H3G 0B1, Canada), Brenna N. Hay (5Department of Biochemistry and Molecular Biology, Michael Smith Laboratories, University of British Columbia, Vancouver, British Columbia, V3T1Z4, Canada.), Leonard J. Foster (5Department of Biochemistry and Molecular Biology, Michael Smith Laboratories, University of British Columbia, Vancouver, British Columbia, V3T1Z4, Canada.), Joaquin Ortega (3Department of Anatomy and Cell Biology, McGill University, Montreal, Quebec H3A 0C7, Canada; 4Centre for Structural Biology, McGill University, Montreal, Quebec H3G 0B1, Canada), Kurt L. Fredrick (1Ohio State Biochemistry Program, 2Center for RNA Biology, The Ohio State University, Columbus, OH 43210, USA, 6Department of Microbiology, The Ohio State University, Columbus, OH 43210, USA.)
Abstract:
Previous studies of the 70S ribosome from Flavobacterium johnsoniae revealed a novel ribosomal protein, bL38, which interacts with uL6 on the 50S subunit. This 5.6 kDa protein is conserved across the Bacteroidia and encoded downstream of bL28 and bL33 in a three-gene operon. Here, we show that bL38 is critical for the growth of F. johnsoniae, and depletion of bL38 leads to accumulation of immature 50S particles which lack uL6 and retain precursor rRNA sequences. Cryo-EM analysis of these particles reveals several putative assembly intermediates, all which show an absence of electron density for uL6 and the entire uL12 stalk base, and additional density corresponding to unprocessed ends of the pre-23S rRNA. One structural class reveals a Der-bound pre-50S intermediate in which the GTPase is tucked behind and appears to reposition helix H68. Extra copies of the uL6 gene can rescue the phenotypes caused by bL38 depletion, strongly suggesting that bL38 facilitates uL6 incorporation during 50S subunit biogenesis. Cryo-EM analysis of 50S particles from this rescued strain reveals nearly twice as many intermediates, suggesting a broader and more robust assembly landscape. Collectively, these data show the importance of bL38 and its role in the assembly of the 50S subunit.
Keywords: 50S Assembly, bL38, Der