Amino acid substitutions affecting protein dynamics in eglin C do not affect heat capacity change upon unfolding

• Published in: Proteins, structure, function, and bioinformatics Vol. 64; no. 2; pp. 295 - 300
• Main Authors: Gribenko, Alexey V., Keiffer, Timothy R., Makhatadze, George I.
• Format: Journal Article
• Language: English
• Published: Hoboken Wiley Subscription Services, Inc., A Wiley Company 01.08.2006
• Subjects: Amino Acid Sequence; Amino Acids - chemistry; Animals; Base Sequence; Calorimetry, Differential Scanning; differential scanning calorimetry; eglin c; heat capacity change; Hot Temperature; Magnetic Resonance Spectroscopy; Molecular Sequence Data; Mutation; Protein Denaturation; protein dynamics; Protein Folding; protein thermodynamics; Proteins - chemistry; Temperature; Thermodynamics
• ISSN: 0887-3585; 1097-0134
• DOI: 10.1002/prot.20974

The heat capacity change upon unfolding (ΔCp) is a thermodynamic parameter that defines the temperature dependence of the thermodynamic stability of proteins; however, physical basis of the heat capacity change is not completely understood. Although empirical surface area‐based calculations can predict heat capacity changes reasonably well, accumulating evidence suggests that changes in hydration of those surfaces is not the only parameter contributing to the observed heat capacity changes upon unfolding. Because packing density in the protein interior is similar to that observed in organic crystals, we hypothesized that changes in protein dynamics resulting in increased rigidity of the protein structure might contribute to the observed heat capacity change upon unfolding. Using differential scanning calorimetry we characterized the thermodynamic behavior of a serine protease inhibitor eglin C and two eglin C variants with altered native state dynamics, as determined by NMR. We found no evidence of changes in ΔCp in either of the variants, suggesting that changes in rigidity do not contribute to the heat capacity change upon unfolding in this model system. Proteins 2006. © 2006 Wiley‐Liss, Inc.