Stay wet, stay stable?

Proteins often host water molecules inside buried cavities or superficial clefts. The presence of these molecules was first resolved via x-ray crystallography and their exchanging dynamics with the external solution was deeply investigated by NMR experiments, the interested readers can dig all the work done by B. Halle and collaborators, see the Halle's web page. Molecular Dynamics simulations also shed light on the molecular mechanisms of this exchange, earlier work by Hummer and Garcia [1] and Sterpone, Ceccarelli and Marchi [2], date back to 2000 or so. It was always questioned the contribution of this set of molecules to the stability of the protein fold. Very recently we decided to tackle the problem and relate it to the issue of protein thermal stability [3]. The starting question was: is the extra stability of a thermophilic protein correlated to its internal hydration. For our study case, the pair of homologous G-domain from the mesophilic E. coli and the hyperthermophilic S. solfataricus, the answer is yes, at least a bit. The manuscript is here.

[1] G. Hummer and A.E. Garcia "Water Penetration and Escape in Proteins". Proteins 2000, 38, 261−272.
[2] F. Sterpone, M. Ceccarelli, M. Marchi, "Dynamics of Hydration in Hen Egg White Lysozyme. J. Mol. Biol. 2001, 311, 409−419.
[3] O. Rahaman, M. Kalimeri, S. Melchionna, J. Henin, F. Sterpone "Role of Internal Water on Protein Thermal Stability: The Case of Homologous G Domains ", J. Phys. Chem. B 2014 in press.