Specificity of Mg2+ binding at the Group II intron branch site

Metal ions play a crucial role in the conformation and splicing activity of Group II introns. Results from 2-aminopurine fluorescence and solution NMR studies suggest that metal ion binding within the branch site region of native D6 of the Group II intron is specific for alkaline earth metal ions an...

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Bibliographic Details
Published in:Biophysical chemistry 2008-08, Vol.136 (2-3), p.96-100
Main Authors: Schlatterer, Jörg C, Greenbaum, Nancy L
Format: Article
Language:English
Subjects:
Introns - genetics
Magnesium - metabolism
Magnetic Resonance Spectroscopy
Nucleic Acid Conformation
RNA - chemistry
RNA - genetics
RNA Splicing
Substrate Specificity
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Summary:Metal ions play a crucial role in the conformation and splicing activity of Group II introns. Results from 2-aminopurine fluorescence and solution NMR studies suggest that metal ion binding within the branch site region of native D6 of the Group II intron is specific for alkaline earth metal ions and involves inner sphere coordination. Although Mg(2+) and Ca(2+) still bind to a mutant stem loop sequence from which the internal loop had been deleted, ion binding to the mutant RNA results in decreased, rather than increased, exposure of the branch site residue to solvent. These data further support the role of the internal loop in defining branch site conformation of the Group II intron. The specific bound Mg(2+) may play a bivalent role: facilitates the extrahelical conformation of the branch site and has the potential to act as a Lewis acid during splicing.
ISSN:0301-4622
DOI:10.1016/j.bpc.2008.05.004