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pH-jump induced leucine zipper folding beyond the diffusion limit.
Mateusz L Donten1, Shabir Hassan, Alexander Popp
1Department of Chemistry, Universität Zürich , Winterthurerstrasse 190, CH-8057 Zürich, Switzerland.
The Journal of Physical Chemistry. B
|December 25, 2014
Summary
This study investigated pH-sensitive leucine zipper folding using a caged proton and time-resolved IR spectroscopy. Covalently linked peptides fold in two steps, revealing insights into protein folding mechanisms.
Area of Science:
- Biochemistry
- Protein Dynamics
- Spectroscopy
Background:
- Leucine zippers are crucial protein structural motifs.
- Understanding protein folding kinetics is vital for molecular biology.
- pH-sensitive protein conformational changes are key to biological function.
Purpose of the Study:
- To investigate the folding kinetics of a pH-sensitive leucine zipper.
- To elucidate the folding mechanism of a GCN4 mutant with eight glutamic acid residues.
- To compare the folding pathways of cross-linked and unlinked peptides.
Main Methods:
- Utilized a caged proton (o-nitrobenzaldehyde, oNBA) for rapid pH jumps.
- Employed time-resolved IR spectroscopy, focusing on the amide I band.
- Investigated covalently linked and unlinked peptides to differentiate folding steps.
Main Results:
- Observed two distinct folding steps occurring on microsecond timescales.
- Identified a partially folded alpha-helix intermediate.
- Demonstrated slower folding for unlinked peptides (∼200 μs) compared to cross-linked ones (∼30 μs).
Conclusions:
- Protein folding proceeds through intermediate states, even in a thermodynamic two-state model.
- Covalent linking significantly impacts coiled-coil formation kinetics.
- The study provides a detailed kinetic picture of leucine zipper folding.
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