Protein attributes contribute to halo-stability, bioinformatics approach

An extremophile is an organism that thrives in, and may even require, physically or geochemically extreme conditions that are detrimental to the majority of life on Earth. The archaeal domain contains renowned examples of extremophiles [1]. A small percentage of proteins can tolerate salinity and desiccation stresses. The enzymes from extremely halophilic organisms represent a fascinating example of adaptation because they can per-form their functions in vivo and in vitro at 4-5 M NaCl, losing activity rapidly when exposed to low salt concentrations [2]. Recently, genes for a number of halophilic enzymes have been cloned, including dihydrofolate reductase from Haloferax volcanii [3], glutamate dehydrogenase from Halobacterium salinarum [4], and malate dehydrogenase from Haloarcula marismortui [5]. Structural features and crystals of some important enzymes in from these organisms such as NAD+-linked opine dehydrogenase[6], glucose dehydrogenase [7], 2Fe-2S ferredoxin [8] and halophilic malate dehydrogenase [9] have been prepared. The molecular mechanisms of halotoleration in these enzymes, however, has not been fully elucidated. Some of the sequenced halophilic enzymes are categorized into the protease family, which contains key enzymes necessary for many critical cellular processes and which are widely used in biotechnology and industrial applications [10]. Information transfer system of archaea has shown gene conservation and differences in the chromosomes and the large extrachromosomal elements among these organisms [11]. Since many members of the archaeal domain are extremophiles, thriving in conditions lethal to most cells, archaea represent an important source of enzymes for applied research and enzymology. For instance, haloarchaea and their enzymes have great potential as biocatalysts in applications requiring low water activity such as reactions with high salt or organic solvent concentrations [12].Development of laboratory techniques such as site-directed m