title: The effects of ionic strength on protein stability: the cold shock protein family.
abstract: Continuum electrostatic models are used to examine in detail the mechanism of protein stabilization and destabilization due to salt near physiological concentrations. Three wild-type cold shock proteins taken from mesophilic, thermophilic, and hyperthermophilic bacteria are studied using these methods. The model is validated by comparison with experimental data collected for these proteins. In addition, a number of single point mutants and three designed sequences are examined. The results from this study demonstrate that the sensitivity of protein stability toward salt is correlated with thermostability in the cold shock protein family. The calculations indicate that the mesophile is stabilized by the presence of salt while the thermophile and hyperthermophile are destabilized. A decomposition of the salt influence at a residue level permits identification of regions of the protein sequences that contribute toward the observed salt-dependent stability. This model is used to rationalize the effect of various point mutations with regard to sensitivity toward salt. Finally, it is demonstrated that designed cold shock protein variants exhibit electrostatic properties similar to the natural thermophilic and hyperthermophilic proteins.
authors.affiliation: Department of Molecular Biology, TPC6, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, CA 92037, USA.
authors.forename: Brian N
authors.initials: BN
authors.lastname: Dominy
authors.forename: Dieter
authors.initials: D
authors.lastname: Perl
authors.forename: Franz X
authors.initials: FX
authors.lastname: Schmid
authors.forename: Charles L
authors.initials: CL
authors.lastname: Brooks
mesh_terms: D000595:Amino Acid Sequence; D001412:Bacillus subtilis / Q000737:chemistry* / Q000235:genetics; D001426:Bacterial Proteins; D006360:Heat-Shock Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D006358:Hot Temperature; D008958:Models, Molecular; D008969:Molecular Sequence Data; D005810:Multigene Family; D009154:Mutation / Q000235:genetics; D009994:Osmolar Concentration; D011487:Protein Conformation / Q000187:drug effects; D011489:Protein Denaturation / Q000187:drug effects; D017510:Protein Folding; D012965:Sodium Chloride / Q000494:pharmacology; D055672:Static Electricity; D013816:Thermodynamics
chemical_list: D001426:Bacterial Proteins; D006360:Heat-Shock Proteins; C407094:cold shock protein, Bacillus; D012965:Sodium Chloride