Insights into the Molecular Basis of Salt Tolerance from the Study of Glutamate Dehydrogenase from Halobacterium salinarum

A homology-based modeling study on the extremely halophilic glutamate dehydrogenase from Halobacterium salinarum has been used to provide insights into the molecular basis of salt tolerance. The modeling reveals two significant differences in the characteristics of the surface of the halophilic enzyme that may contribute to its stability in high salt. The first of these is that the surface is decorated with acidic residues, a feature previously seen in structures of halophilic enzymes. The second is that the surface displays a significant reduction in exposed hydrophobic character. The latter arises not from a loss of surface-exposed hydrophobic residues, as has previously been proposed, but from a reduction in surface-exposed lysine residues. This is the first report of such an observation.