CD measurement of aqueous protein solution at high temperature up to 180 °C —Thermodynamic analysis of thermophilic protein by pressure-proof cell compartment

Abstract

During investigation of thermal transitions of peptides and proteins, the transition temperature is occasionally too high to trace the whole transition profile. In order to solve this problem and perform conformational analysis at high temperature, we have recently developed a pressure-proof cell compartment for circular dichroism measurements. Here we demonstrate how well this system works to collect CD spectra, at high temperature up to 180 °c in aqueous solution. Ribosome recycling factor (RRF), which consists of two domains; three stranded α-helix bundle domain (Domain I) and β α/β domain (Domain II), was used as an example. We constructed models of isolated Domain I substituting Domain II with tripeptide (Gly-Gly-Gly) and compared these models from mesophilic and thermophilic bacteria. The melting profiles of these models revealed that thermal stability is enhanced by the increased enthalpy provided by hydrogen bonds and ionic pairing.