Conformational studies on a hyperthermostable enzyme

The structural features of the hyperthermophilic endo-ß-1,3-glucanase from Pyrococcus furiosus were studied using circular dichroism, steady-state and time-resolved fluorescence spectroscopy and anisotropy. Upon heat and chemical treatment the folded and denatured states of the protein were characterized by distinguishable spectral profiles that identified a number of conformational states. The fluorescence methods showed that the spectral differences arose from changes in the local environment around specific tryptophan residues in the native, partially folded, partially unfolded and completely unfolded state. A structural resemblance was observed between the native protein and the structurally perturbed state which resulted after heat treatment at 110 °C. The enzyme underwent disruption of the native secondary and tertiary structure only after incubation at biologically extremely high temperatures (i.e. 150 °C), whilst in the presence of 8 m of guanidine hydrochloride the protein was partially unfolded.