Exploring the Free Energy and Conformational Landscape of tRNA at High Temperature and Pressure

A combined temperature- and pressure-dependent study was employed to reveal the conformational and free-energy landscape of phenylalanine transfer RNA (tRNA(Phe)), a known model for RNA function, to elucidate the features that are essential in determining its stability. These studies also help explore its structural properties under extreme environmental conditions, such as low/high temperatures and high pressures. To this end, fluorescence and FTIR spectroscopies, calorimetric and small-angle scattering measurements were carried out at different ion concentrations over a wide range of temperatures and pressures up to several hundred MPa. Compared with the pronounced temperature effect, the pressure-dependent structural changes of tRNA(Phe) are small. A maximum of only 15% unpaired bases is observed upon pressurization up to 1 GPa. RNA unfolding differs not only from protein unfolding, but also from DNA melting. Its pressure stability seems to be similar to that of noncanonical DNA structures.