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Investigation of the thermal unfolding of secondary and tertiary structure in E. coli tRNA fMet by high‐resolution nmr
Author(s) -
Wong K. Lim,
Wong Yeng P.,
Kearns David R.
Publication year - 1975
Publication title -
biopolymers
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.556
H-Index - 125
eISSN - 1097-0282
pISSN - 0006-3525
DOI - 10.1002/bip.1975.360140407
Subject(s) - chemistry , transfer rna , protein tertiary structure , base pair , protein secondary structure , crystallography , nuclear magnetic resonance spectroscopy , molecule , resolution (logic) , base (topology) , stereochemistry , rna , dna , biochemistry , organic chemistry , mathematical analysis , mathematics , artificial intelligence , computer science , gene
The high‐resolution (300 MHz) proton nmr spectrum of E. coli tRNA fMet has been examined in 0.17 M NaCl, with and without Mg 2+ , and at various temperatures. In light of recent studies of other E. coli tRNA and fragments of tRNA fMet , some low field (11–15 ppm) resonances previously assigned to secondary structure base pairs are reassigned to a tertiary structure A 14 –S 4 U 8 base pair and a protected uridine residue in the anticodon loop. These two resonances and other low field resonances which are assigned to secondary structure base pairs are used to monitor the thermal unfolding of the molecule. In the absence of Mg 2+ the tertiary structure base pair is present only to ∼45°C, but in the presence of Mg 2+ it remains until at least 70°C. Analysis of the temperature dependence of other low field resonances indicates that the melting of the dihydrouridine stem occurs more or less simultaneously with the loss of tertiary structure. The observation of the resonance from the A 14 –S 4 U 8 base pair proves that tertiary structure is present in this molecule below 40°C, even in the absence of Mg 2+ .