Asymmetric Kinetics of Protein Structural Changes Export

@article{citeulike:4381249, abstract = {PMID: 19378977 Thermodynamic and kinetic understanding of structural transformations in proteins is critical to new developments in medicine and biotechnology. These fields often require the design of mechanism-based modulators of protein function. Researchers increasingly consider these structural changes—such as folding/unfolding or shuttling between active and inactive states—within the energy landscape concept that supposes a high-dimensional, rugged conformational surface. The unevenness, or asperity, of this conformational surface results from energetic barriers and kinetic traps. However, for a large number of protein reactions, such as reversible folding/unfolding, the literature only reports simple two-state transitions, which calls into question the use of a more complex energy landscape model. The question is: are these reactions really that simple, or are we misled by a biased experimental approach? In this Account, we argue in favor of the latter possibility. Indeed, the frequently employed temperature-jump method only allows recording protein structure changes in the heating direction. Under those conditions, it might not be possible to detect other kinetic pathways that could have been taken in the cooling direction. Recently, however, we have developed bidirectional pressure- and temperature-jump methods, which can offer new insights. Here, we show the potential of these methods both for studying protein folding/unfolding reactions, taking ribonuclease A as model, and for studying functionally relevant protein conformational changes, using the open/closed allosteric transition of tryptophan synthase. For example, the heating and cooling temperature-jump induced kinetics involved in the folding/unfolding conformational surface of ribonuclease A is illustrated above. In both of our model systems, the kinetic transition states of several reaction steps were path-dependent, i.e. the rates and thermodynamic activation parameters depend on the direction of the applied pressure and temperature perturbation. This asymmetry suggests that proteins cope with external stress by adapting their structure to form different ensembles of conformational substates. These states are distinguished by their activation enthalpy and entropy barriers, which can be strongly negative in the folding direction. Based on our analysis of activation compressibility and heat capacity, hydration and packing defects of the kinetic transition states are also very important for determining the reaction path. We expect that a more generalized use of this experimental approach should allow researchers to obtain greater insight into the mechanisms of physiologically relevant protein structural changes.}, author = {Marchal, Stéphane and Font, Josep and Ribó, Marc and Vilanova, Maria and Phillips, Robert S. and Lange, Reinhard and Torrent, Joan}, citeulike-article-id = {4381249}, citeulike-linkout-0 = {http://dx.doi.org/10.1021/ar800266r}, citeulike-linkout-1 = {http://pubs.acs.org/doi/abs/10.1021/ar800266r}, citeulike-linkout-2 = {http://view.ncbi.nlm.nih.gov/pubmed/19378977}, citeulike-linkout-3 = {http://www.hubmed.org/display.cgi?uids=19378977}, day = {16}, doi = {10.1021/ar800266r}, issn = {1520-4898}, journal = {Accounts of Chemical Research}, keywords = {activation, active-state, binding\_kinetics, conformational\_changes, dynamics, energy\_landscape, kinetics, pathway}, month = {June}, number = {6}, pages = {778--787}, posted-at = {2009-10-28 09:14:43}, priority = {2}, title = {Asymmetric Kinetics of Protein Structural Changes}, url = {http://dx.doi.org/10.1021/ar800266r}, volume = {42}, year = {2009} }

TY - JOUR ID - citeulike:4381249 L3 - citeulike-article-id:4381249 N2 - PMID: 19378977 Thermodynamic and kinetic understanding of structural transformations in proteins is critical to new developments in medicine and biotechnology. These fields often require the design of mechanism-based modulators of protein function. Researchers increasingly consider these structural changes—such as folding/unfolding or shuttling between active and inactive states—within the energy landscape concept that supposes a high-dimensional, rugged conformational surface. The unevenness, or asperity, of this conformational surface results from energetic barriers and kinetic traps. However, for a large number of protein reactions, such as reversible folding/unfolding, the literature only reports simple two-state transitions, which calls into question the use of a more complex energy landscape model. The question is: are these reactions really that simple, or are we misled by a biased experimental approach? In this Account, we argue in favor of the latter possibility. Indeed, the frequently employed temperature-jump method only allows recording protein structure changes in the heating direction. Under those conditions, it might not be possible to detect other kinetic pathways that could have been taken in the cooling direction. Recently, however, we have developed bidirectional pressure- and temperature-jump methods, which can offer new insights. Here, we show the potential of these methods both for studying protein folding/unfolding reactions, taking ribonuclease A as model, and for studying functionally relevant protein conformational changes, using the open/closed allosteric transition of tryptophan synthase. For example, the heating and cooling temperature-jump induced kinetics involved in the folding/unfolding conformational surface of ribonuclease A is illustrated above. In both of our model systems, the kinetic transition states of several reaction steps were path-dependent, i.e. the rates and thermodynamic activation parameters depend on the direction of the applied pressure and temperature perturbation. This asymmetry suggests that proteins cope with external stress by adapting their structure to form different ensembles of conformational substates. These states are distinguished by their activation enthalpy and entropy barriers, which can be strongly negative in the folding direction. Based on our analysis of activation compressibility and heat capacity, hydration and packing defects of the kinetic transition states are also very important for determining the reaction path. We expect that a more generalized use of this experimental approach should allow researchers to obtain greater insight into the mechanisms of physiologically relevant protein structural changes. IS - 6 JF - Accounts of Chemical Research SN - 1520-4898 EP - 787 TI - Asymmetric Kinetics of Protein Structural Changes VL - 42 SP - 778 KW - activation KW - active-state KW - binding_kinetics KW - conformational_changes KW - dynamics KW - energy_landscape KW - kinetics KW - pathway AU - Marchal, Stéphane AU - Font, Josep AU - Ribó, Marc AU - Vilanova, Maria AU - Phillips, Robert AU - Lange, Reinhard AU - Torrent, Joan PY - 2009/06/16/ UR - http://dx.doi.org/10.1021/ar800266r ER -