Free energy barrier estimation of unfolding the alpha-helical surfactant-associated polypeptide C

Proteins
R ZangiA E Mark

Abstract

Molecular dynamics simulations were conducted to estimate the free energy barrier of unfolding surfactant-associated polypeptide C (SP-C) from an alpha-helical conformation. Experimental studies indicate that while the helical fold of SP-C is thermodynamically stable in phospholipid micelles, it is metastable in a mixed organic solvent of CHCl3/CH3OH/0.1 M HCl at 32:64:5 (v/v/v), in which it undergoes an irreversible transformation to an insoluble aggregate that contains beta-sheet. On the basis of experimental observations, the free energy barrier was estimated to be approximately 100 kJ/mole by applying Eyring's transition state theory to the experimental rate of unfolding [Protein Sci 1998;7:2533-2540]. These studies prompted us to carry out simulations to investigate the unwinding process of two helical turns encompassing residues 25-32 in water and in methanol. The results give an upper bound estimation for the free energy barrier of unfolding of SP-C of approximately 20 kJ/mole. The results suggest a need to reconsider the applicability of a single-mode activated process theory to protein unfolding.

References

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Citations

Oct 22, 2003·Proceedings of the National Academy of Sciences of the United States of America·Jack Schonbrun, Ken A Dill
Jan 31, 2006·Biophysical Journal·Eunice RamírezGustavo E López
May 7, 2020·Scientific Reports·Shayon BhattacharyaDamien Thompson
Mar 4, 2014·Physical Review. E, Statistical, Nonlinear, and Soft Matter Physics·Ronen Zangi
Oct 11, 2013·Journal of Chemical Information and Modeling·Catarina A CarvalhedaAntónio M Baptista

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