Applications of pressure perturbation calorimetry to study factors contributing to the volume changes upon protein unfolding.
BACKGROUND
Pressure perturbation calorimetry (PPC) is a biophysical method that allows direct determination of the volume changes upon conformational transitions in macromolecules.
This review provides novel details of the use of PPC to analyze unfolding transitions in proteins. The emphasis is made on the data analysis as well as on the validation of different structural factors that define the volume changes upon unfolding. Four case studies are presented that show the application of these concepts to various protein systems.


CONCLUSIONS
The major conclusions are: 1. Knowledge of the thermodynamic parameters for heat induced unfolding facilitates the analysis of the PPC profiles. 2. The changes in the thermal expansion coefficient upon unfolding appear to be temperature dependent.3.Substitutions on the protein surface have negligible effects on the volume changes upon protein unfolding. 4. Structural plasticity of proteins defines the position dependent effect of amino acid substitutions of the residues buried in the native state. 5. Small proteins have positive volume changes upon unfolding which suggests difference in balance between the cavity/void volume in the native state and the hydration volume changes upon unfolding as compared to the large proteins that have negative volume changes.


CONCLUSIONS
The information provided here gives a better understanding and deeper insight into the role played by various factors in defining the volume changes upon protein unfolding.
Center for Biotechnology and Interdisciplinary Studies, Rensselaer Polytechnic Institute, Troy, NY 12180, USA; Howard P. Isermann Department of Chemical and Biological Engineering, Rensselaer Polytechnic Institute, Troy, NY, 12180, USA.
Pranav P
PP
Pandharipande
Center for Biotechnology and Interdisciplinary Studies, Rensselaer Polytechnic Institute, Troy, NY 12180, USA; Department of Biological Sciences, Rensselaer Polytechnic Institute, Troy, NY, 12180, USA. Electronic address: makhag@rpi.edu.
George I
GI
Makhatadze
D017766:Acid Anhydride Hydrolases / Q000737:chemistry* / Q000235:genetics; D000595:Amino Acid Sequence; D000818:Animals; D007611:Aprotinin / Q000737:chemistry* / Q000235:genetics; D002151:Calorimetry / Q000379:methods; D002417:Cattle; D002942:Circular Dichroism; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism; D015870:Gene Expression; D006358:Hot Temperature; D008958:Models, Molecular; D008969:Molecular Sequence Data; D011489:Protein Denaturation; D017510:Protein Folding; D055550:Protein Stability; D058767:Protein Unfolding; D011506:Proteins / Q000138:chemical synthesis / Q000737:chemistry*; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics; D016415:Sequence Alignment; D013696:Temperature; D013816:Thermodynamics; D025801:Ubiquitin / Q000737:chemistry* / Q000235:genetics; D000097024:Acylphosphatase
D017766:Acid Anhydride Hydrolases; D007611:Aprotinin; D011506:Proteins; D011994:Recombinant Proteins; D025801:Ubiquitin; D000097024:Acylphosphatase; C539234:Trpzip2 protein
Expansivity; Pressure perturbation calorimetry; Protein folding; Protein stability; Volume changes