A Model for the Stabilization of a Halophilic Protein
The process of protein folding from polypeptide to active structure is largely determined by solvent interactions. Proteins with the same function but from different organisms would have evolved different interaction tactics, each appropriate for the particular solvent environment, in order to achieve an identical active site configuration. Enzymes from the extreme halophiles perform the same functions as their counterparts from other organisms but under conditions of extreme salinity; in halobacteria, for example, the cytoplasm is saturated in KC1. In solvents containing molar salt concentrations, “nonhalophilic” proteins are likely to be aggregated, to precipitate, or even to unfold, depending on the type of salt. Halophilic proteins, however, unfold if the solvent salt concentration falls below a certain value (2.5 M KC1, for example), still a very high concentration if judged by more usual physiological standards. They are good models for the study of solvent effect contributions to the structure and stability of proteins and of the adaptation mechanisms underlying them.
KeywordsEntropy Crystallization Hydrated Enthalpy Sedimentation
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