This article reviews a specific model of mesophilic protein stability and explores consequences on the stability of thermophilic proteins. The model hinges on the Kauzmann-Tanford framework of the hydrophobic transfer, for which modifications are proposed on consideration of thermodynamic regularities common to liquid N-alkyl- amides and an enlarged set of mesophilic proteins. The innovative consideration of two additional energetic terms contributes to clarify controversial aspects and misconceptions linked to the concept of hydrophobicity. The major conclusions that can be inferred suggest that: i) there is no structural preference driving the stability of proteins to elevated temperatures; ii) associating systems seem to better tolerate elevated temperatures; iii) the adaptation of proteins to extreme thermal environments requires shifting and broadening of their free energy/temperature profiles. In the light of experimental findings accumulated to date, these results seem encouraging enough to suggest that the model proposed may provide a reasonable insight into the kind and magnitude of forces controlling protein organization.
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