Document Type

Journal Article

Date of this Version

5-29-2009

Publication Source

Journal of Molecular Biology

Volume

389

Issue

1

Start Page

90

Last Page

102

DOI

10.1016/j.jmb.2009.03.074

Abstract

Metals are the most commonly encountered protein cofactors, and they play important structural and functional roles in biology. In many cases, metal binding provides a major driving force for a polypeptide chain to fold. While there are many studies on the structure, stability, and function of metal-binding proteins, there are few studies focusing on understanding the kinetic mechanism of metal-induced folding. Herein, the Zn(2+)-induced folding kinetics of a small zinc-binding protein are studied; the CH1(1) peptide is derived from the first cysteine/histidine-rich region (CH1 domain) of the protein interaction domains of the transcriptional coregulator CREB-binding protein. Computational design is used to introduce tryptophan and histidine mutations that are structurally consistent with CH1(1); these mutants are studied using stopped-flow tryptophan fluorescence experiments. The Zn(2+)-induced CH1(1) folding kinetics are consistent with two parallel pathways, where the initial binding of Zn(2+) occurs at two sites. However, the initially formed Zn(2+)-bound complexes can proceed either directly to the folded state where zinc adopts a tetrahedral coordination or to an off-pathway misligated intermediate. While elimination of those ligands responsible for misligation simplifies the folding kinetics, it also leads to a decrease in the zinc binding constant. Therefore, these results suggest why these nonnative zinc ligands in the CH1(1) motif are conserved in several distantly related organisms and why the requirement for function can lead to kinetic frustration in folding. In addition, the loop closure rate of the CH1(1) peptide is determined based on the proposed model and temperature-dependent kinetic measurements.

Copyright/Permission Statement

© 2009. This manuscript version is made available under the CC-BY-NC-ND 4.0 license http://creativecommons.org/licenses/by-nc-nd/4.0/

Keywords

Amino Acid Sequence, Carrier Proteins, Circular Dichroism, Coenzymes, Histidine, Hydrogen-Ion Concentration, Kinetics, Magnetic Resonance Spectroscopy, Models, Molecular, Molecular Sequence Data, Mutant Proteins, Mutation, Peptides, Protein Folding, Protein Structure, Tertiary, Spectrometry, Fluorescence, Thermodynamics, Titrimetry, Tryptophan

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Date Posted: 07 December 2016

This document has been peer reviewed.