title: Role of 16S ribosomal RNA methylations in translation initiation in Escherichia coli.
abstract: Translation initiation from the ribosomal P-site is the specialty of the initiator tRNAs (tRNA(fMet)). 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 tRNA(fMet) 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.
authors.affiliation: Department of Microbiology and Cell Biology, Indian Institute of Science, Bangalore, Karnataka, India.
authors.forename: Gautam
authors.initials: G
authors.lastname: Das
authors.forename: Dinesh Kumar
authors.initials: DK
authors.lastname: Thotala
authors.forename: Suman
authors.initials: S
authors.lastname: Kapoor
authors.forename: Sheelarani
authors.initials: S
authors.lastname: Karunanithi
authors.forename: Suman S
authors.initials: SS
authors.lastname: Thakur
authors.forename: N Sadananda
authors.initials: NS
authors.lastname: Singh
authors.forename: Umesh
authors.initials: U
authors.lastname: Varshney
mesh_terms: D045103:5,10-Methylenetetrahydrofolate Reductase (FADH2) / Q000096:biosynthesis / Q000235:genetics; D019943:Amino Acid Substitution / Q000235:genetics; D001483:Base Sequence; D029968:Escherichia coli Proteins / Q000096:biosynthesis / Q000235:genetics*; D008745:Methylation; D008969:Molecular Sequence Data; D009154:Mutation; D010442:Peptide Chain Initiation, Translational / Q000235:genetics*; D012329:RNA, Bacterial / Q000378:metabolism; D012336:RNA, Ribosomal, 16S / Q000378:metabolism* / Q000502:physiology; D012358:RNA, Transfer, Met / Q000235:genetics; D012270:Ribosomes / Q000378:metabolism*
chemical_list: D029968:Escherichia coli Proteins; D012329:RNA, Bacterial; D012336:RNA, Ribosomal, 16S; D012358:RNA, Transfer, Met; D045103:5,10-Methylenetetrahydrofolate Reductase (FADH2); C472209:metf protein, E coli