PMID:14654706
| Citation |
Seetharaman, M, Williams, C, Cramer, CJ and Musier-Forsyth, K (2003) Effect of G-1 on histidine tRNA microhelix conformation. Nucleic Acids Res. 31:7311-21 |
|---|---|
| Abstract |
Histidine tRNAs (tRNA(His)) are unique in that they possess an extra 5'-base (G-1) not found in other tRNAs. Deletion of G-1 results in at least a 250-fold reduction in the rate of histidine charging in vitro. To better understand the role of the G-1 nucleotide in defining the structure of tRNA(His), and to correlate structure with cognate amino acid charging, NMR and molecular dynamics (MD) studies were performed on the wild-type and a DeltaG-1 mutant Escherichia coli histidine tRNA acceptor stem microhelix. Using NMR-derived distance restraints, global structural characteristics are described and interpreted to rationalize experimental observations with respect to aminoacylation activity. The quality of the NMR-derived solution conformations of the wild-type and DeltaG-1 histidine microhelices (micro helix(His)) is assessed using a variety of MD-based computational protocols. Most of the duplex regions of the acceptor stem and the UUCG tetraloop are well defined and effectively superimposable for the wild-type and DeltaG-1 mutant microhelix(His). Differences, however, are observed at the end of the helix and in the single-stranded CCCA-3' tail. The wild-type microhelix(His) structure is more well defined than the mutant and folds into a 'stacked fold-back' conformation. In contrast, we observe fraying of the first two base pairs and looping back of the single-stranded region in the DeltaG-1 mutant resulting in a much less well defined conformation. Thus the role of the extra G-1 base of the unique G-1:C73 base pair in tRNA(His) may be to prevent end-fraying and stabilize the stacked fold-back conformation of the CCCA-3' region. |
| Links | |
| Keywords |
Base Sequence; Escherichia coli/genetics; Models, Molecular; Molecular Sequence Data; Nuclear Magnetic Resonance, Biomolecular; Nucleic Acid Conformation; Point Mutation/genetics; RNA Stability; RNA, Bacterial/chemistry; RNA, Bacterial/genetics; RNA, Transfer, Amino Acyl/chemistry; RNA, Transfer, Amino Acyl/genetics |
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