title: A Simple Mechanism Underlying the Effect of Protecting Osmolytes on Protein Folding.
abstract: Osmolytes are small organic compounds that confer to the cell an enhanced adaptability to external conditions. Many osmolytes not only protect the cell from osmotic stress but also stabilize the native structure of proteins. While simplified models able to predict changes to protein stability are available, a general physicochemical explanation of the underlying microscopic mechanism is still missing. Here, we address this issue by performing very long all-atom MD simulations, free energy calculations, and experiments on a well-characterized mini-protein, the villin headpiece. Comparisons between the folding free energy landscapes in pure water and osmolyte solutions, together with experimental validation by means of circular dichroism, unfolding experiments, and NMR, led us to formulate a simple hypothesis for the protecting mechanism. Taken together, our results support a novel mechanistic explanation according to which the main driving force behind native state protection is a change in the solvent rotational diffusion.
authors.affiliation: Dipartimento di Chimica Fisica ed Elettrochimica, Universita' degli Studi di Milano , Via Golgi 19, 20133 Milano, Italy.
authors.forename: G
authors.initials: G
authors.lastname: Saladino
authors.affiliation: Structural Biology and Biocomputing Programme, Spanish National Cancer Research Centre (CNIO), c/Melchor Fernandez Almagro 3, 28029, Madrid, Spain.
authors.forename: M
authors.initials: M
authors.lastname: Marenchino
authors.affiliation: Dipartimento di Chimica Fisica ed Elettrochimica, Universita' degli Studi di Milano , Via Golgi 19, 20133 Milano, Italy.|INSTM Research Unit , Via Golgi 19, 20133 Milano, Italy.
authors.forename: S
authors.initials: S
authors.lastname: Pieraccini
authors.affiliation: Structural Biology and Biocomputing Programme, Spanish National Cancer Research Centre (CNIO), c/Melchor Fernandez Almagro 3, 28029, Madrid, Spain.
authors.forename: R
authors.initials: R
authors.lastname: Campos-Olivas
authors.affiliation: Dipartimento di Chimica Fisica ed Elettrochimica, Universita' degli Studi di Milano , Via Golgi 19, 20133 Milano, Italy.|INSTM Research Unit , Via Golgi 19, 20133 Milano, Italy.|Institute of Molecular Science and Technology , Via Golgi 19, 20133 Milano.
authors.forename: M
authors.initials: M
authors.lastname: Sironi
authors.affiliation: Structural Biology and Biocomputing Programme, Spanish National Cancer Research Centre (CNIO), c/Melchor Fernandez Almagro 3, 28029, Madrid, Spain.
authors.forename: F L
authors.initials: FL
authors.lastname: Gervasio