Probing Small Heat Shock Protein Chaperoning Activity Through the Interaction Between Myoglobin and Guanidine Hydrochloride

Myoglobin is a small biological protein found in most muscle tissues. When in the proper form (native/folded), myoglobin can serve its primary function: binding oxygen. However, like all proteins, myoglobin can denature through a variety of processes into a form that no longer binds oxygen. One denaturant, guanidine hydrochloride (GuHCl), is the biological product of protein metabolism. Another class of biological proteins is small heat shock proteins (sHSPs), which have the function of chaperoning other proteins to prevent the denaturing process. Previously, in physical chemistry lab, we explored the GuHCl-induced denaturing of myoglobin. Former Northwestern students used fluorescence correlation spectroscopy (FCS) to investigate the chaperoning activity of sHSPs. In this project, we consider the combination of the two efforts to evaluate if our version of sHSP protects myoglobin from denaturing. In particular, we spectroscopically examine the interactions between GuHCl and a complex formed between myoglobin and the sHSP Mj HSP16.5. This sHSP was extracted from Methanocaldococcus jannaschii, an archaebacterium, and labeled with the fluorescent dye AF488. Ultraviolet-visible (UV-Vis) spectroscopy and FCS are used to gain insight into the chaperoning activity of Mj HSP16.5 and the denaturing mechanism of GuHCl