Contrasting Effects of Guanidinium Chloride and Urea on the Activity and Unfolding of Lysozyme

Biswas, Biswajit and Muttathukattil, Aswathy N and Reddy, Govardhan and Singh, Prashant Chandra (2018) Contrasting Effects of Guanidinium Chloride and Urea on the Activity and Unfolding of Lysozyme. In: ACS OMEGA, 3 (10). pp. 14119-14126.

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Abstract

Cosolvents play an important role in regulating the stability and function of proteins present in the cell. We studied the role of cosolvents, urea and guanidinium chloride (GdmCl), which act as protein denaturants, in the catalytic activity and structural stability of the protein lysozyme using activity measurements, spectroscopy, and molecular dynamics simulations. We find that the activity of lysozyme increases on the addition of urea, whereas it decreases sharply on the addition of GdmCl. At low GdmCl concentrations (GdmCl] < 4 M), the activity of lysozyme decreases, even though there is no significant perturbation in the structure of the lysozyme folded state. We find that this is due to the strong interaction of the Gdm(+) ion with the residues Asp52 and Glu35, which are present in the lysozyme catalytic site. In contrast, urea interacts with Trp63 present in the loop region present near the active site of lysozyme, inducing minor conformational changes in lysozyme, which can increase the activity of lysozyme. At higher denaturant concentrations, experiments show that GdmCl completely denatures the protein, whereas the folded state is stable in the presence of urea. We further show that GdmCl denatures lysozyme with the disulfide bonds intact in the protein, whereas urea denatures the protein only when the disulfide bonds are broken using reducing agents.

Item Type:	Journal Article
Publication:	ACS OMEGA
Publisher:	AMER CHEMICAL SOC
Additional Information:	Copy right for this article belong to AMER CHEMICAL SOC
Department/Centre:	Division of Chemical Sciences > Solid State & Structural Chemistry Unit
Date Deposited:	30 Nov 2018 14:49
Last Modified:	30 Nov 2018 14:49
URI:	http://eprints.iisc.ac.in/id/eprint/61191

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