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Equilibrium amide hydrogen exchange and protein folding kinetics
1Laboratory of Biochemistry, National Cancer Institute, NIH, Bethesda, MD 20892-4255, USA. Yawen@helix.nih.gov
Journal of Biomolecular NMR
|November 5, 1999
Summary
This study extends the Linderstrøm-Lang hydrogen exchange (HX) model. It reveals how protein folding kinetics influence HX behaviors (EX1 and EX2) in three-state systems, particularly on-pathway intermediates.
Area of Science:
- Biochemistry
- Chemical Kinetics
- Protein Dynamics
Background:
- The Linderstrøm-Lang model describes hydrogen exchange (HX) in proteins.
- HX experiments probe protein structure and dynamics.
- Understanding HX behavior in multi-state systems is crucial.
Purpose of the Study:
- Extend the classical HX model to three-state protein folding systems.
- Investigate the relationship between HX behaviors (EX1, EX2) and folding kinetics.
- Clarify the role of intermediates in HX phenomena.
Main Methods:
- Theoretical extension of the Linderstrøm-Lang HX model.
- Analysis of amide proton exchange in native (N), intermediate (I), and unfolded (U) states.
- Modeling of on-pathway (U<-->I<-->N) and off-pathway (I<-->U<-->N) systems.
Main Results:
- In off-pathway systems, intermediates do not affect HX behavior.
- In on-pathway systems, stable intermediates significantly impact HX.
- Refolding rates from intermediate to native states are critical for EX1/EX2 determination.
Conclusions:
- Protein folding intermediates profoundly influence HX behavior in on-pathway systems.
- Both refolding rates (U to I and I to N) are key determinants of HX patterns.
- Caution is advised when inferring folding kinetics from equilibrium HX data.