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pH-Jump Induced Leucine Zipper Folding beyond the Diffusion Limit


Donten, Mateusz L; Hassan, Shabir; Popp, Alexander; Halter, Jonathan; Hauser, Karin; Hamm, Peter (2015). pH-Jump Induced Leucine Zipper Folding beyond the Diffusion Limit. Journal of Physical Chemistry B, 119(4):1425-1432.

Abstract

The folding of a pH-sensitive leucine zipper, that is, a GCN4 mutant containing eight glutamic acid residues, has been investigated. A pH-jump induced by a caged proton (o-nitrobenzaldehyde, oNBA) is employed to initiate the process, and time-resolved IR spectroscopy of the amide I band is used to probe it. The experiment has been carefully designed to minimize the buffer capacity of the
sample solution so that a large pH jump can be achieved, leading to a transition from a completely unfolded to a completely folded state with a single laser shot. In
order to eliminate the otherwise rate-limiting diffusion-controlled step of the association of two peptides, they have been covalently linked. The results for the folding kinetics of the cross-linked peptide are compared with those of an unlinked peptide, which reveals a detailed picture of the folding mechanism. That is, folding
occurs in two steps, one on an ∼1−2 μs time scale leading to a partially folded α-helix even in the monomeric case and a second one leading to the final coiled-coil structure on distinctively different time scales of ∼30 μs for the cross-linked peptide and ∼200 μs for the unlinked peptide. By varying the initial pH, it is found that the folding mechanism is consistent with a thermodynamic two-state model, despite the fact that a transient intermediate is observed in the kinetic experiment.

Abstract

The folding of a pH-sensitive leucine zipper, that is, a GCN4 mutant containing eight glutamic acid residues, has been investigated. A pH-jump induced by a caged proton (o-nitrobenzaldehyde, oNBA) is employed to initiate the process, and time-resolved IR spectroscopy of the amide I band is used to probe it. The experiment has been carefully designed to minimize the buffer capacity of the
sample solution so that a large pH jump can be achieved, leading to a transition from a completely unfolded to a completely folded state with a single laser shot. In
order to eliminate the otherwise rate-limiting diffusion-controlled step of the association of two peptides, they have been covalently linked. The results for the folding kinetics of the cross-linked peptide are compared with those of an unlinked peptide, which reveals a detailed picture of the folding mechanism. That is, folding
occurs in two steps, one on an ∼1−2 μs time scale leading to a partially folded α-helix even in the monomeric case and a second one leading to the final coiled-coil structure on distinctively different time scales of ∼30 μs for the cross-linked peptide and ∼200 μs for the unlinked peptide. By varying the initial pH, it is found that the folding mechanism is consistent with a thermodynamic two-state model, despite the fact that a transient intermediate is observed in the kinetic experiment.

Citations

6 citations in Web of Science®
6 citations in Scopus®
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Additional indexing

Item Type:Journal Article, refereed, original work
Communities & Collections:07 Faculty of Science > Department of Chemistry
Dewey Decimal Classification:540 Chemistry
Language:English
Date:2015
Deposited On:16 Sep 2015 10:44
Last Modified:05 Apr 2016 19:23
Publisher:American Chemical Society (ACS)
ISSN:1520-5207
Funders:Swiss National Foundation (SNP), European Research Council (ERC) Advanced Investigator Grant (DYNALLO), Deutsche Forschungsgemeinschaft
Publisher DOI:https://doi.org/10.1021/jp511539c

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