Nucleoside Modifications Stabilize Mg2+ Binding in Escherichia coli tRNAVal: An Imino Proton NMR Investigation
| Autor: | Jack Horowitz, Agustin Kintanar, Dongxian Yue |
|---|---|
| Rok vydání: | 1994 |
| Předmět: |
Conformational change
Binding Sites Magnetic Resonance Spectroscopy Base Sequence Stereochemistry Chemistry Base pair Molecular Sequence Data Temperature RNA Nuclear magnetic resonance spectroscopy medicine.disease_cause Biochemistry Transfer RNA Escherichia coli medicine Proton NMR Magnesium Protons Binding site RNA Transfer Val |
| Zdroj: | Biochemistry. 33:8905-8911 |
| ISSN: | 1520-4995 0006-2960 |
| Popis: | The structures of in vitro transcribed Escherichia coli tRNA(Val), which lacks base modifications, and the native tRNA, which contains them, are very similar in the presence of excess Mg2+ (Kintanar, Yue, and Horowitz, unpublished results). To further probe the effects of base modifications on the structure of tRNA, the Mg2+ ion dependence of the downfield region of the 1H NMR spectrum of in vitro transcribed E. coli tRNA(Val) in aqueous phosphate buffer was investigated. The spectra indicate a remarkable conformational change in unmodified E. coli tRNA(Val) coincident with binding or release of Mg2+. Assignment of the imino proton resonances in the low Mg2+ form of the tRNA transcript allows a detailed description of the conformational change. There is near total disruption of the D stem and tertiary interactions in the absence of bound Mg2+. A new strong interaction between the U67-A6 base pair and the G50-U64 wobble pair is observed, indicating a substantial structural rearrangement at the junction of the acceptor and T stems. The binding constants of the strong Mg2+ binding sites in the D loop and near the D stem in unmodified tRNA(Val) are at least 2 orders of magnitude less than in tRNAVal containing base modifications. The metal ion binding site in the anticodon loop is somewhat stronger than metal ion binding sites in the D loop and stem in unmodified tRNA(Val), but it is still weaker than all strong Mg2+ binding sites in native tRNA(Val). Thus, one role of the base modifications found in tRNA is to stabilize or strengthen the Mg2+ binding sites.(ABSTRACT TRUNCATED AT 250 WORDS) |
| Databáze: | OpenAIRE |
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