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Category: Applied and Industrial Microbiology; Environmental Microbiology
Molecular Adaptation to High Salt, Page 1 of 2
< Previous page | Next page > /docserver/preview/fulltext/10.1128/9781555815813/9781555814229_Chap19-1.gif /docserver/preview/fulltext/10.1128/9781555815813/9781555814229_Chap19-2.gifAbstract:
This chapter presents the insights into adaptation provided by the study of the four genomes of extreme halophiles sequenced to date. The focus then shifts to molecular adaptation of halophilic proteins, defined as proteins isolated from extreme halophiles. Different aspects concerning solvation, stabilization of the folded and associated assemblies of proteins, and salt effect is presented. Molecular adaptation of the iron translocation function to high salt would be obtained by the replacement of acidic side chains by the more basic His residues. A number of hyperthermophilic Archaea accumulates moderate salt concentration in their cytosol. The three-dimensional structures of their proteins share some of the features emphasized for halophilic proteins. The dynamics of soluble and membrane proteins from extreme halophiles has been studied extensively with the aim of understanding the molecular mechanisms leading to stability, solubility, and activity in highly concentrated salt environments. Studies reported in other sections of this chapter have shown that soluble proteins from extremely halophilic Archaea are active and soluble in a wide range of solvent salt conditions with varying stability. Extreme halophilic organisms require high salt concentrations for growth. They accumulate multimolar salt concentrations in their cytosol to counterbalance the high osmotic pressure of their environment.
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Mean-square fluctuations ‹u 2› in Hm MalDH measured by neutron scattering. ‹u 2› values are plotted as a function of temperature for three different solvent conditions: 2 M NaCl D2O (circles), 2 M KCl D2O (triangles), and 2 M NaCl H2O (diamonds). (Modified from Tehei et al., 2001 , with permission from the publisher.)
Halophilic proteins with available high-resolution structures
Ions detected and net charge of halophilic proteins with an X-ray structure
Salt-adapted proteins from nonextreme halophile with available high-resolution structures
Composition of the solvation shell of Hm MalDH a