Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.1.27.5 (RNase)
 17,967 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Native mass spectrometry is widely used to probe the structures, stabilities, and stoichiometries of proteins and biomolecular complexes in aqueous solutions, typically containing volatile ammonium acetate or ammonium bicarbonate buffer. In this study, nanoelectrospray emitters with submicron tips are used to produce significantly desalted ions of RNase A and a reduced, alkylated form of this protein, RA-RNase A, from solutions containing 175 mM ammonium acetate, as well as sodium chloride and Tris containing solutions with the same nominal ionic strength and pH. The charge-state distributions formed by nanoelectrospray ionization and tyrosine fluorescence emission data as a function of temperature from these solutions indicate that the folded form of RA-RNase A in solution is stabilized when ammonium acetate is replaced by increasing quantities of NaCl and Tris. Ion mobility data for the 7+ charge state of RA-RNase A indicates that the protein conformation in ammonium acetate changes with increasing concentration of NaCl which stablizes more compact structures. These results are consistent with observations reported 130 years ago by Hofmeister who found that ion identity can affect the stabilities and the structures of proteins in solution. This study indicates the importance of buffer choice when interpreting native mass spectrometry data.
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PMID:Native mass spectrometry beyond ammonium acetate: effects of nonvolatile salts on protein stability and structure. 3088 8

The effects of sodium thiocyanate, sodium chloride, and sodium sulfate on the ribonuclease barnase were studied using differential scanning calorimetry (DSC) and NMR. Both measurements reveal specific and saturable binding at low anion concentrations (up to 250 mM), which produces localized conformational and energetic effects that are unrelated to the Hofmeister series. The binding of sulfate slows intramolecular motions, as revealed by peak broadening in 13C heteronuclear single quantum coherence spectroscopy. None of the anions shows significant binding to hydrophobic groups. Above 250 mM, the DSC results are consistent with the expected Hofmeister effects in that the chaotropic anion thiocyanate destabilizes barnase. In this higher concentration range, the anions have approximately linear effects on protein NMR chemical shifts, with no evidence for direct interaction of the anions with the protein surface. We conclude that the effects of the anions on barnase are mediated by solvent interactions. The results are not consistent with the predictions of the preferential interaction, preferential hydration, and excluded volume models commonly used to describe Hofmeister effects. Instead, they suggest that the Hofmeister anion effects on both stability and solubility of barnase are due to the way in which the protein interacts with water molecules, and in particular with water dipoles, which are more ordered around sulfate anions and less ordered around thiocyanate anions.
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PMID:Molecular Mechanism for the Hofmeister Effect Derived from NMR and DSC Measurements on Barnase. 3145 55


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