Article
- The EMBO Journal (2008) 27, 840 - 851
- doi:10.1038/emboj.2008.20
Published online: 21 February 2008
Role of 16S ribosomal RNA methylations in translation initiation in Escherichia coli
Gautam Das1, Dinesh Kumar Thotala1, Suman Kapoor1, Sheelarani Karunanithi1, Suman S Thakur1,2, N Sadananda Singh1 and Umesh Varshney1
- Department of Microbiology and Cell Biology, Indian Institute of Science, Bangalore, Karnataka, India
Correspondence to:
Umesh Varshney, Department of Microbiology and Cell Biology, Indian Institute of Science, CNR Rao Circle, Bangalore, Karnataka 560012, India. Tel.: +91 80 2293 2686; Fax: +91 80 2360 2697; E-mail: varshney@mcbl.iisc.ernet.in
2Molecular Biophysics Unit, Indian Institute of Science, Bangalore, Karnataka 560012, India
Received 16 August 2007; Accepted 18 January 2008
Abstract
Translation initiation from the ribosomal P-site is the specialty of the initiator tRNAs (tRNAfMet). Presence of the three consecutive G-C base pairs (G29-C41, G30-C40 and G31-C39) in their anticodon stems, a highly conserved feature of the initiator tRNAs across the three kingdoms of life, has been implicated in their preferential binding to the P-site. How this feature is exploited by ribosomes has remained unclear. Using a genetic screen, we have isolated an Escherichia coli strain, carrying a G122D mutation in folD, which allows initiation with the tRNAfMet containing mutations in one, two or all the three G-C base pairs. The strain shows a severe deficiency of methionine and S-adenosylmethionine, and lacks nucleoside methylations in rRNA. Targeted mutations in the methyltransferase genes have revealed a connection between the rRNA modifications and the fundamental process of the initiator tRNA selection by the ribosome.
Keywords:
- S-adenosyl-L-methionine,
- 5,10 methylene tetrahydrofolate dehydrogenase,
- methyltransferase,
- modified nucleoside,
- folD
