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Coupled Binding and Helix Formation Monitored by Synchrotron-Radiation Circular Dichroism
Elin Karlsson1, Eva Andersson1, Nykola C Jones2
1Department of Medical Biochemistry and Microbiology, Uppsala University, Uppsala, Sweden.
Biophysical Journal
|August 6, 2019
Summary
Intrinsically disordered proteins gain structure upon binding. This study reveals helix formation occurs rapidly during protein binding, with a stabilized intermediate observed at high ionic strength, providing insights into coupled folding and binding mechanisms.
Area of Science:
- Biochemistry and Molecular Biology
- Structural Biology
Background:
- Intrinsically disordered proteins (IDPs) are crucial for cellular regulation and signaling.
- IDPs often adopt specific structures upon binding to target proteins through coupled folding and binding reactions.
Purpose of the Study:
- To investigate the mechanisms of coupled folding and binding reactions in intrinsically disordered proteins.
- To study helix formation during the binding of the nuclear coactivator binding domain and the activator of thyroid hormone and retinoid receptors.
Main Methods:
- Utilized stopped-flow synchrotron-radiation circular dichroism (CD) spectroscopy to monitor rapid helix formation.
- Employed fluorescence-monitored binding experiments to analyze kinetic phases.
- Performed simulations of mechanistic models to interpret experimental data.
Main Results:
- Demonstrated rapid helix formation concurrent with protein association.
- Identified a concentration-independent kinetic phase, indicative of a stabilized intermediate at high ionic strength.
- Showed that the intermediate likely involves structural rearrangement with minimal helicity changes.
Conclusions:
- Synchrotron-radiation CD spectroscopy is a feasible technique for mechanistic studies of protein-protein interactions.
- The findings provide a benchmark for computational simulations of coupled binding reactions.
- Understanding these mechanisms is vital for deciphering cellular regulation and signaling pathways involving IDPs.
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