Abstract
The effects of guanidine hydrochloride (GdnHCl) on the structure and stability of the D-galactose/D-glucose-binding protein fromEscherichia coli(GGBP) and its complex with D-glucose (GGBP/Glc) were investigated by intrinsic protein fluorescence and far-UV circular dichroism (CD). The role of calcium in the stability of the protein structure was also studied. It was shown that the processes of GGBP and GGBP/Glc unfolding induced by GdnHCl followed one-step reversible denaturation mechanism. The obtained data showed that the binding of glucose to GGBP resulted in an increase of the protein stability towards the actions of the GdnHCl which made protein unfolding more cooperative. The stabilities of GGBP alone, GGBP in the presence of glucose, GGBP-depleted calcium (GGBP-Ca), and GGBP/Glc-depleted calcium (GGBP/Glc-Ca) were characterized by difference of Gibbs free energies.
Highlights
Protein folding remains one of the most intriguing problems of molecular biology [4,9]. When it seemed that we were quite near the explanation of protein folding in compact globular structure it appeared that many proteins in principle cannot have such structure alone, without their partners [13,14]
This paper is focused on the study of the unfolding–refolding mechanisms of D-galactose/D-glucosebinding protein from Escherichia coli (GGBP) alone and in the presence of glucose (GGBP/Glc) induced by guanidine hydrochloride (GdnHCl)
We investigated the role of other ligand – calcium ion localized in the loop of the C-terminal domain, in the structure and folding process of protein
Summary
Protein folding remains one of the most intriguing problems of molecular biology [4,9] When it seemed that we were quite near the explanation of protein folding in compact globular structure it appeared that many proteins in principle cannot have such structure alone, without their partners (other proteins, DNA molecules and inorganic ligand) [13,14]. In view of this new concept it is interesting to study the role of ligands in proteins structure and stability. Investigation of GGBP structure and stability is of interest both for basic science and biotechnology as this protein is good candidate for a sensing element of the biosensor system for permanent non-invasive monitoring of glucose content in the blood of diabetic patients
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