Related Experiment Videos
Efficient, pH-dependent RNA ligation by the VS ribozyme in trans.
Aileen C McLeod1, David M J Lilley
1Cancer Research UK Nucleic Acid Structure Research Group, Department of Biochemistry, MSI/WTB Complex, The University of Dundee, UK.
Biochemistry
|January 28, 2004
Summary
The VS ribozyme efficiently ligates substrates in trans when a helix prevents dissociation. Nucleotide C755 is crucial for ligation, and pH affects reaction rates, suggesting protonation states influence catalysis.
Area of Science:
- Biochemistry
- Molecular Biology
- Enzymology
Background:
- The VS ribozyme is a catalytic RNA molecule with ligase activity.
- Ribozyme function is influenced by substrate structure and reaction conditions.
Purpose of the Study:
- To investigate the mechanism of trans ligation by the VS ribozyme.
- To identify key nucleotides and reaction parameters affecting ligation efficiency.
Main Methods:
- Enzymatic assays to measure ligation and cleavage rates.
- Site-directed mutagenesis to alter ribozyme sequence (e.g., C755A).
- pH dependence studies to determine reaction kinetics.
Main Results:
- Extended helix Ia in the substrate (>or=10 bp) enhances trans ligation to ~80%.
- Nucleotide C755 is critical for ligation, with C755A variant showing a 70-fold reduced ligation rate.
- Trans ligation rate is pH-dependent, with a pK(A) of 5.6, suggesting protonation states influence catalysis.
- A756 is implicated in substrate binding or catalysis.
Conclusions:
- VS ribozyme trans ligation is highly efficient when substrate dissociation is prevented.
- C755 plays a specific role in organizing ligation substrate termini.
- The ribozyme likely catalyzes ligation in its deprotonated state and cleavage in its protonated state, with A756 as a potential protonation site.