Mg2+ ions differently affect the physical properties of tRNA (Phe) and the transcript of its gene
Serebrov, V.I.; Vasilenko, K.S.; Kholod, N.S.; Kiselev, L.L.
Molekuliarnaia Biologiia 31(5): 894-900
1997
ISSN/ISBN: 0026-8984 PMID: 9454076 Document Number: 479218
Transfer RNAs isolated from cells always contain modified nucleosides (minors) occupying specific positions in the primary structure. As for the transcripts of tRNA genes enzymatically synthesized in vitro, those are free from minors. Therefore, comparing mature tRNAs and the transcripts enables to identify the role of modifications in creating the spatial structure of tRNA. In this paper, the mature tRNAPhe from E. coli is compared with the gene transcript of the same tRNA. Analysis of differential melting curves showed that unlike mature tRNA, at low Mg2+ concentration (<1 mM), the transcript lacked some elements of spatial structure. Spectra of circular dichroism and. absorption indicated different sensitivity of the secondary structure of the two forms of tRNA to binding divalent cations, while the character of structural transitions remained similar. Measurement of hydrodynamic dimensions of mature tRNA and the transcript showed a weak influence of modifications on the general shape of molecule. The post-transcriptional modifications proved to have a significant effect on the local conformation of the molecule in the presence of divalent cations, while not altering the three-dimensional structure of the tRNA molecule.