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Published on: November 25, 2015
Allosteric communication network in the tetrameric restriction endonuclease Bse634I
Mindaugas Zaremba1, Giedrius Sasnauskas, Claus Urbanke
1Institute of Biotechnology, Graiciuno 8, Vilnius, LT-02241, Lithuania.
Journal of Molecular Biology
|September 22, 2006
Summary
Restriction endonuclease Bse634I activity is regulated by communication signals between its protein subunits. Mutations reveal inhibitory and activating signals controlling enzyme function.
Area of Science:
- Biochemistry
- Molecular Biology
- Enzymology
Background:
- Restriction endonuclease Bse634I is a homotetramer composed of two primary dimers.
- Maximum catalytic efficiency occurs when Bse634I binds two DNA copies, one per dimer.
- Down-regulation of activity on single DNA sites results from cross-talk between dimers, but signal propagation mechanisms are unclear.
Purpose of the Study:
- To identify communication pathways regulating Bse634I tetramer catalytic activity.
- To investigate the role of the dimer-dimer interface in signal propagation.
- To characterize the oligomeric state and catalytic properties of Bse634I mutants.
Main Methods:
- Site-directed mutagenesis of amino acid residues at the dimer-dimer interface.
- Analysis of protein oligomeric state.
- Kinetic analysis of enzyme activity using various DNA substrates (hairpin oligonucleotide, one- and two-site plasmids).
Main Results:
- Mutations N262A and V263A at the tetramerization interface did not disrupt tetramer assembly.
- These mutations significantly altered Bse634I catalytic properties, despite the distal location from the active site.
- Two distinct communication signals were identified: an inhibitory "stopper" signal and an activating "sync" signal.
Conclusions:
- The dimer-dimer interface is crucial for transmitting regulatory signals in Bse634I.
- The interplay between "stopper" and "sync" signals dictates enzyme activity and regulation.
- Understanding these signals provides insight into the allosteric regulation of restriction endonucleases.
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