Distinct conformational dynamics and allosteric networks in alpha tryptophan synthase during active catalysis
Kathleen F O'Rourke1, Rebecca N D'Amico1, Debashish Sahu1
1Department of Chemistry, The Pennsylvania State University, University Park, Pennsylvania, USA.
Protein Science : a Publication of the Protein Society
|December 14, 2020
Summary
Enzyme dynamics during catalysis reveal crucial allosteric networks. Analyzing a variant showed that substrate and product states alone don't fully explain these complex protein motions.
Area of Science:
- Biochemistry and enzymology
- Structural biology
- Protein dynamics
Background:
- Enzymes function under dynamic chemical equilibrium, with active turnover involving both forward and reverse reactions.
- Protein motions and allosteric networks are critical for enzyme catalysis.
- Previous studies analyzed tryptophan synthase alpha subunit dynamics using NMR under turnover conditions.
Purpose of the Study:
- To investigate the inactive D60N variant of tryptophan synthase alpha subunit.
- To deconvolute the contributions of substrate-bound and product-bound states to the enzyme's working state dynamics.
- To understand the role of chemical bond formation/breakage in enzyme conformational changes.
Main Methods:
- Nuclear Magnetic Resonance (NMR) spectroscopy was used to analyze conformational dynamics.
- The study focused on the inactive D60N variant of the alpha subunit of tryptophan synthase.
- Comparison of dynamics in substrate-bound (E:IGP) and product-bound (E:indole:G3P) states versus the working state.
Main Results:
- The D60N substitution induced minor structural and dynamic changes.
- The D60N variant in substrate- and product-bound states did not fully replicate the dynamics of the working state.
- Enzyme transitions involve quenching of millisecond conformational exchange and formation of new allosteric connections.
Conclusions:
- The act of chemical bond transformation, not just substrate/product binding, significantly alters enzyme structure and dynamics.
- Structural ordering and new allosteric connections emerge during the transition from substrate to product states.
- These changes are potentially vital for coordinating product channeling to the beta subunit.
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