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.
KeywordsNeutron Scattering Malate Dehydrogenase Solvent Interaction Halophilic Bacterium Solvent Density
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- Baldacci G, Guinet F, Tillit J, Zaccai G, de Recondo AM (1990) Functional implications related to the gene structure of the elongation factor EF-Tu from Halobacterium marismortui. Nucleic Acids Res 18: 507–511Google Scholar
- Hippel PH von, Schleich T (1969) The effects of neutral salts on the structure and conformational stability of macromolecules in solution. In: TimasheffSN, Fasman GD (eds) Structure and stability of biological macromolecules. Marcel Dekker, New York, pp 417–574Google Scholar
- Mevarech M, Neumann E (1977) Malate dehydrogenase from extremely halophilic bacteria of the Dead Sea. 2. Effect of salt on the catalytic activity and structure. Biochemistry 16: 3786–3791Google Scholar
- Mevarech M, Eisenberg H, Neumann E (1977) Malate dehydrogenase isolated from extremely halophilic bacteria of the Dead Sea. 1. Purification and molecular characterization. Biochemistry 16: 3781–3785Google Scholar
- Pundak S, Aloni H, Eisenberg H (1981) Structure and activity of malate dehydrogenase from the extreme halophilic bacteria of the Dead Sea. 2. Inactivation, dissociation and unfolding at NaCl concentrations below 2M salt. Salt concentration and temperature dependence of enzyme stability. Eur J Biochem 118: 471–477Google Scholar