ИСТИНА

A tremendous diversity of ligand binding proteins creates considerable opportunities for their scientific and medicinal applications [1]. Ligand-binding proteins of the bacterial periplasm (PBPs) share a characteristic two-lobed structure and undergo a large conformational change as a result of ligand binding. Utilization of the E.coli D-galactose/D-glucose-binding protein (GGBP) as the sensitive element in the glucose biosensor is one of the promising directions for continuous glucose monitoring. As GGBP binds glucose with high affinity (Kd = 1 μM), the necessity to lower the affinity of GGBP to glucose should be taken into account in the development of methods to monitor the glucose level in human blood. Still, wild-type GGBP can be used as a sensitive element of biosensor systems in which blood or interstitial liquid sampling is connected with considerable dilution [2]. In this work we considered that interaction of GGBP with its ligand is affected by viscosity of solution. At unfolding-refolding of complex GGBP with glucose (GGBP/Glc) induced by guanidine hydrochloride (GdnHCl) a marked deceleration of the equilibrium acquisition between the native GGBP/Glc and the unfolded protein is seen in contrast to GGBP alone. The presence of glycerin similarly influences on the protein-ligand interaction. This effect is not revealed at heat-induced GGBP/Glc denaturation. These testify that the limiting step of the unfolding-refolding process of the complex GGBP/Glc is the disruption/tuning of the configuration fit between the native state of GGBP and glucose with the process rate depending on denaturant concentration. The obtained data should be taken into account at GGBP using as sensing probe of glucose biosensor.