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Mapping long-range contacts in a highly unfolded protein.
Michael A Lietzow1, Marc Jamin, H Jane Dyson
1Department of Molecular Biology and Skaggs Institute for Chemical Biology, The Scripps Research Institute, La Jolla, CA 92037, USA.
Journal of Molecular Biology
|September 25, 2002
Summary
Studying the acid-unfolded state of apomyoglobin reveals early protein folding events. Even denatured, the protein shows transient compact states with native-like contacts between its N and C termini.
Area of Science:
- Biochemistry
- Structural Biology
- Protein Dynamics
Background:
- Understanding protein folding is crucial for biological processes.
- The earliest events in protein folding remain challenging to study.
- Unfolded or partly folded protein states offer insights into folding pathways.
Purpose of the Study:
- To characterize the structure of the acid-unfolded state of apomyoglobin.
- To investigate conformational propensities in denatured protein states.
- To identify early protein folding events and transient structures.
Main Methods:
- Paramagnetic spin labeling using nitroxide side-chains.
- Nuclear Magnetic Resonance (NMR) spectroscopy.
- Site-directed mutagenesis to introduce cysteine residues at positions 18, 77, and 133.
Main Results:
- The N and C termini of acid-unfolded apomyoglobin exhibit significant interactions.
- The central region of the polypeptide chain behaves as a random polymer.
- Transient compact states with native-like N- and C-terminal contacts are observed in the denatured form.
Conclusions:
- Early protein folding events involve specific interactions even in denatured states.
- Apomyoglobin's unfolded state is not entirely random, displaying structured elements.
- Conformational propensities in denatured states provide a window into the initial stages of protein folding.