Proteins can now be constructed with any amino acid sequence. The importance of applications of this technology in health and other areas is now clear and limited mostly by our current knowledge and imagination. Thus, it is essential that we learn to predict how changes in the amino acid sequence will affect the function, folding, and stability of a protein. The primary goal of this project is to gain a better understanding of the forces that contribute to the conformational stability of globular proteins and to use this information to develop methods to increase their stability. This requires a thorough understanding of the structures of the folded and unfolded conformations of proteins and of the effect of changes in structure on the equilibrium between these states. To this end, we will continue to study the effect of small changes in the amino acid sequence on the conformations of the folded and unfolded states, and on the thermodynamics of folding of five microbial ribonucleases: RNase Sa, RNase Sa2, RNase Sa3, RNase T1, and RNase Ba, also known as barnase. Some of the questions we hope to answer are: 1) Can mutations such as Phe yields Tyr that add hydrogen bonds to folded proteins be used to increase their stability? 2) Can mutations such as Gly yields Thr that both reduce the conformational entropy of the unfolded state and bury nonpolar surface area or form hydrogen bonds in the folded state be used to increase protein stability? 3) Can an I to I+4 interaction between glutamine and aspartate side chains on the exposed face of an alpha- helix be used to increase protein stability? 4) Can we double the conformational stability of ab RNase without reducing the enzymic activity? 5) How does the net charge on a protein effect its conformational stability and other physical and chemical properties? 6) What determines the pK values of the ionizable groups in folded and unfolded proteins and how do they effect the conformational stability?

National Institute of Health (NIH)
National Institute of General Medical Sciences (NIGMS)
Research Project (R01)
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Molecular and Cellular Biophysics Study Section (BBCA)
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Wehrle, Janna P
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Texas A&M University
Schools of Medicine
College Station
United States
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Nick Pace, C; Scholtz, J Martin; Grimsley, Gerald R (2014) Forces stabilizing proteins. FEBS Lett 588:2177-84
Pace, C Nick; Fu, Hailong; Lee Fryar, Katrina et al. (2014) Contribution of hydrogen bonds to protein stability. Protein Sci 23:652-61
Pace, C Nick; Fu, Hailong; Fryar, Katrina Lee et al. (2011) Contribution of hydrophobic interactions to protein stability. J Mol Biol 408:514-28
Fu, Hailong; Grimsley, Gerald; Scholtz, J Martin et al. (2010) Increasing protein stability: importance of DeltaC(p) and the denatured state. Protein Sci 19:1044-52
Nick Pace, C; Huyghues-Despointes, Beatrice M P; Fu, Hailong et al. (2010) Urea denatured state ensembles contain extensive secondary structure that is increased in hydrophobic proteins. Protein Sci 19:929-43
Grimsley, Gerald R; Scholtz, J Martin; Pace, C Nick (2009) A summary of the measured pK values of the ionizable groups in folded proteins. Protein Sci 18:247-51
Scholtz, J Martin; Grimsley, Gerald R; Pace, C Nick (2009) Solvent denaturation of proteins and interpretations of the m value. Methods Enzymol 466:549-65
Fu, Hailong; Grimsley, Gerald R; Razvi, Abbas et al. (2009) Increasing protein stability by improving beta-turns. Proteins 77:491-8
Alston, Roy W; Lasagna, Mauricio; Grimsley, Gerald R et al. (2008) Peptide sequence and conformation strongly influence tryptophan fluorescence. Biophys J 94:2280-7
Trevino, Saul R; Scholtz, J Martin; Pace, C Nick (2008) Measuring and increasing protein solubility. J Pharm Sci 97:4155-66

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