Measuring residual dipolar couplings at high hydrostatic pressure: robustness of alignment media to high pressure

Combining High-Pressure Perturbation with NMR Spectroscopy for a Structural and Dynamical Characterization of Protein Folding Pathways

High-hydrostatic pressure is an alternative perturbation method that can be used to destabilize globular proteins. Generally perfectly reversible, pressure exerts local effects on regions or domains of a protein containing internal voids, contrary to heat or chemical denaturant that destabilize protein structures uniformly. When combined with NMR spectroscopy, high pressure (HP) allows one to monitor at a residue-level resolution the structural transitions occurring upon unfolding and to determine the kinetic properties of the process. The use of HP-NMR has long been hampered by technical difficulties. Owing to the recent development of commercially available high-pressure sample cells, HP-NMR experiments can now be routinely performed. This review summarizes recent advances of HP-NMR techniques for the characterization at a quasi-atomic resolution of the protein folding energy landscape.

Practical aspects of high-pressure NMR spectroscopy and its applications in protein biophysics and structural biology

Pressure and temperature are the two fundamental variables of thermodynamics. Temperature and chemical perturbation are central experimental tools for the exploration of macromolecular structure and dynamics. Though it has long been recognized that hydrostatic pressure offers a complementary and often unique view of macromolecular structure, stability and dynamics, it has not been employed nearly as much. For solution NMR applications the limited use of high-pressure is undoubtedly traced to difficulties of employing pressure in the context of modern multinuclear and multidimensional NMR. Limitations in pressure tolerant NMR sample cells have been overcome and enable detailed studies of macromolecular energy landscapes, hydration, dynamics and function. Here we review the practical considerations for studies of biological macromolecules at elevated pressure, with a particular emphasis on applications in protein biophysics and structural biology.

Monitoring protein folding through high pressure NMR spectroscopy

High-pressure is a well-known perturbation method used to destabilize globular proteins. It is perfectly reversible, which is essential for a proper thermodynamic characterization of a protein equilibrium. In contrast to other perturbation methods such as heat or chemical denaturant that destabilize protein structures uniformly, pressure exerts local effects on regions or domains of a protein containing internal cavities. When combined with NMR spectroscopy, hydrostatic pressure offers the possibility to monitor at a residue level the structural transitions occurring upon unfolding and to determine the kinetic properties of the process. High-pressure NMR experiments can now be routinely performed, owing to the recent development of commercially available high-pressure sample cells. This review summarizes recent advances and some future directions of high-pressure NMR techniques for the characterization at atomic resolution of the energy landscape of protein folding.

High-pressure NMR techniques for the study of protein dynamics, folding and aggregation

High-pressure is a well-known perturbation method used to destabilize globular proteins and dissociate protein complexes or aggregates. The heterogeneity of the response to pressure offers a unique opportunity to dissect the thermodynamic contributions to protein stability. In addition, pressure perturbation is generally reversible, which is essential for a proper thermodynamic characterization of a protein equilibrium. When combined with NMR spectroscopy, hydrostatic pressure offers the possibility of monitoring at an atomic resolution the structural transitions occurring upon unfolding and determining the kinetic properties of the process. The recent development of commercially available high-pressure sample cells greatly increased the potential applications for high-pressure NMR experiments that can now be routinely performed. This review summarizes the recent applications and future directions of high-pressure NMR techniques for the characterization of protein conformational fluctuations, protein folding and the stability of protein complexes and aggregates.

Pressure-induced structural transition of mature HIV-1 protease from a combined NMR/MD simulation approach

We investigate the pressure-induced structural changes in the mature human immunodeficiency virus type 1 protease dimer, using residual dipolar coupling (RDC) measurements in a weakly oriented solution. (1)DNH RDCs were measured under high-pressure conditions for an inhibitor-free PR and an inhibitor-bound complex, as well as for an inhibitor-free multidrug resistant protease bearing 20 mutations (PR20). While PR20 and the inhibitor-bound PR were little affected by pressure, inhibitor-free PR showed significant differences in the RDCs measured at 600 bar compared with 1 bar. The structural basis of such changes was investigated by MD simulations using the experimental RDC restraints, revealing substantial conformational perturbations, specifically a partial opening of the flaps and the penetration of water molecules into the hydrophobic core of the subunits at high pressure. This study highlights the exquisite sensitivity of RDCs to pressure-induced conformational changes and illustrates how RDCs combined with MD simulations can be used to determine the structural properties of metastable intermediate states on the folding energy landscape.