Presence and location of modified nucleotides in Escherichia coli tmRNA: structural mimicry with tRNA acceptor branches.
EMBO J
; 17(11): 3188-96, 1998 Jun 01.
Article
in En
| MEDLINE
| ID: mdl-9606200
ABSTRACT
Escherichia coli tmRNA functions uniquely as both tRNA and mRNA and possesses structural elements similar to canonical tRNAs. To test whether this mimicry extends to post-transcriptional modification, the technique of combined liquid chromatography/ electrospray ionization mass spectrometry (LC/ESIMS) and sequence data were used to determine the molecular masses of all oligonucleotides produced by RNase T1 hydrolysis with a mean error of 0.1 Da. Thus, this allowed for the detection, chemical characterization and sequence placement of modified nucleotides which produced a change in mass. Also, chemical modifications were used to locate mass-silent modifications. The native E.coli tmRNA contains two modified nucleosides, 5-methyluridine and pseudouridine. Both modifications are located within the proposed tRNA-like domain, in a seven-nucleotide loop mimicking the conserved sequence of T loops in canonical tRNAs. Although tmRNA acceptor branches (acceptor stem and T stem-loop) utilize different architectural rules than those of canonical tRNAs, their conformations in solution may be very similar. A comparative structural and functional analysis of unmodified tmRNA made by in vitro transcription and native E.coli tmRNA suggests that one or both of these post-transcriptional modifications may be required for optimal stability of the acceptor branch which is needed for efficient aminoacylation.
Full text:
1
Collection:
01-internacional
Health context:
3_ND
Database:
MEDLINE
Main subject:
RNA, Bacterial
/
RNA, Transfer
/
Escherichia coli
/
Nucleic Acid Conformation
Language:
En
Journal:
EMBO J
Year:
1998
Document type:
Article