Biochemical, Structural, and Molecular Genetic Aspects of Halophilism

Abstract

The study of halobacteria relates to a better understanding of evolutionary relationships. Halophilic enzymes are very unstable in low salt concentrations. Because some of the important fractionation methods in protein chemistry, such as electrophoresis or ion-exchange chromatography, cannot be applied at high salt concentrations, the available fractionation methods are limited. The existing purification procedures fall into two groups: the nonhalophilic approach and the halophilic approach. This chapter reviews the developments in the molecular characterization of halobacterial proteins, starting with the methodology of their purification. The biochemical and biophysical structural analyses of some enzymatic systems for which extensive knowledge is accumulated is described.. Macromolecular structures from halophilic bacteria are discussed to improve the understanding of the molecular mechanisms of adaptation to high salt concentration environments by considering genome organization, genetic tools, isolation of genes, or transcript organization, and structure. The structural aspects of halophilism can be determined by ribosomal subunits, surface layers, purple membrane, or halophilic malate dehydrogenase.