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J Biol Chem. 2019 Nov 8;294(45):16942-16952. doi: 10.1074/jbc.RA119.009742. Epub 2019 Oct 3.

Binding-induced folding under unfolding conditions: Switching between induced fit and conformational selection mechanisms.

Author information

1
National Centre for Biological Sciences, Tata Institute of Fundamental Research, Bengaluru 560065, India Indian Institute of Science Education and Research, Pune, Pashan, Pune 411 008, India.
2
National Centre for Biological Sciences, Tata Institute of Fundamental Research, Bengaluru 560065, India Indian Institute of Science Education and Research, Pune, Pashan, Pune 411 008, India jayant@iiserpune.ac.in.

Abstract

The chemistry of protein-ligand binding is the basis of virtually every biological process. Ligand binding can be essential for a protein to function in the cell by stabilizing or altering the conformation of a protein, particularly for partially or completely unstructured proteins. However, the mechanisms by which ligand binding impacts disordered proteins or influences the role of disorder in protein folding is not clear. To gain insight into this question, the mechanism of folding induced by the binding of a Pro-rich peptide ligand to the SH3 domain of phosphatidylinositol 3-kinase unfolded in the presence of urea has been studied using kinetic methods. Under strongly denaturing conditions, folding was found to follow a conformational selection (CS) mechanism. However, under mildly denaturing conditions, a ligand concentration-dependent switch in the mechanism was observed. The folding mechanism switched from being predominantly a CS mechanism at low ligand concentrations to being predominantly an induced fit (IF) mechanism at high ligand concentrations. The switch in the mechanism manifests itself as an increase in the reaction flux along the IF pathway at high ligand concentrations. The results indicate that, in the case of intrinsically disordered proteins too, the folding mechanism is determined by the concentration of the ligand that induces structure formation.

KEYWORDS:

Src homology 3 domain (SH3 domain); conformational selection; induced fit; intrinsically disordered protein; ligand-binding protein; peptides; protein folding; reaction flux

PMID:
31582563
PMCID:
PMC6851327
[Available on 2020-11-08]
DOI:
10.1074/jbc.RA119.009742

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