ИСТИНА

An investigation of folding of proteins with β-barrel topology is of high fundamental importance. Despite an increasing number of studies on the stability and unfolding processes of proteins with β-barrel topology, these processes have been understood to a much lesser extent than for α- and α/β-proteins. A large group of odorant-binding proteins (OBPs) share a common nine-stranded β-barrel structure which encloses a ligand binding site composed of an internal cavity and an external loop scaffold. OBPs also attract high scientific interest as promising building blocks for construction of optical biosensors for dangerous substances such as toxic, explosive molecules and so on. It is notable that an essential stability to different denaturing conditions of any proteins being intended for utilization as a sensitive element of any biosensor system is of high importance. This work is focused on the study of dimeric bovine OBP (bOBP) which in contrast to classical OBPs is characterized by a unique folding pattern that involves the crossing of the α-helical domain of each monomer over the β-barrel of the other. In this work we studied the guanidine hydrochloride (GdnHCl) induced denaturation-renaturation of recombinant bOBP using spectroscopic methods and size-exclusion chromatography. It was shown that bOBP possesses high resistance to denaturing action of GdnHCl. We revealed that formation of two native-like states of bOBP precedes the full unfolding of the protein globule. These local changes of bOBP in the region of pre-denaturing GdnHCl concentrations did not result in alteration of the protein capability to bind ligand.