Shah, RA and Varada, R and Sah, S and Shetty, S and Lahry, K and Singh, S and Varshney, U (2019) Rapid formylation of the cellular initiator tRNA population makes a crucial contribution to its exclusive participation at the step of initiation. In: Nucleic acids research, 47 (4). pp. 1908-1919.
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Abstract
Initiator tRNAs (i-tRNAs) possess highly conserved three consecutive GC base pairs (GC/GC/GC, 3GC pairs) in their anticodon stems. Additionally, in bacteria and eukaryotic organelles, the amino acid attached to i-tRNA is formylated by Fmt to facilitate its targeting to 30S ribosomes. Mutations in GC/GC/GC to UA/CG/AU in i-tRNACUA/3GC do not affect its formylation. However, the i-tRNACUA/3GC is non-functional in initiation. Here, we characterised an Escherichia coli strain possessing an amber mutation in its fmt gene (fmtam274), which affords initiation with i-tRNACUA/3GC. Replacement of fmt with fmtam274 in the parent strain results in production of truncated Fmt, accumulation of unformylated i-tRNA, and a slow growth phenotype. Introduction of i-tRNACUA/3GC into the fmtam274 strain restores accumulation of formylated i-tRNAs and rescues the growth defect of the strain. We show that i-tRNACUA/3GC causes a low level suppression of am274 in fmtam274. Low levels of cellular Fmt lead to compromised efficiency of formylation of i-tRNAs, which in turn results in distribution of the charged i-tRNAs between IF2 and EF-Tu allowing the plasmid borne i-tRNACUA/3GC to function at both the initiation and elongation steps. We show that a speedy formylation of i-tRNA population is crucial for its preferential binding (and preventing other tRNAs) into the P-site. © The Author(s) 2019. Published by Oxford University Press on behalf of Nucleic Acids Research.
| Item Type: | Journal Article |
|---|---|
| Publication: | Nucleic acids research |
| Publisher: | NLM (Medline) |
| Additional Information: | Copyright for this article belongs to NLM (Medline) |
| Department/Centre: | Division of Biological Sciences > Microbiology & Cell Biology |
| Date Deposited: | 08 Apr 2019 11:26 |
| Last Modified: | 08 Apr 2019 11:26 |
| URI: | http://eprints.iisc.ac.in/id/eprint/62007 |
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