Premium
Anion binding to the ubiquitin molecule
Author(s) -
Makhatadze George I.,
Lopez Marin M.,
Richardson John M.,
Thmos Susan T.
Publication year - 1998
Publication title -
protein science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.353
H-Index - 175
eISSN - 1469-896X
pISSN - 0961-8368
DOI - 10.1002/pro.5560070318
Subject(s) - chemistry , circular dichroism , molecule , thermostability , enthalpy , crystallography , ion , differential scanning calorimetry , biochemistry , organic chemistry , thermodynamics , enzyme , physics
Effects of different salts (NaCl, MgCl 2 , CaCl 2 , GdmCl, NaBr, NaC1O 4 , NaH 2 PO 4 , Na 2 SO 4 ) on the stability of the ubiquitin molecule at pH 2.0 have been studied by differential scanning calorimetry, circular dichroism, and Tyr fluorescence spectroscopies. It is shown that all of the salts studied significantly increase the thermostability of the ubiquitin molecule, and that this stabilization can be interpreted in terms of anion binding. Estimated thermodynamic parameters of binding for Cl − show that this binding is relatively weak ( K d = 0.15 M) and is characterized by a negative enthalpy of ‐15 kJ/mol per site. Particularly surprising was the observed stabilizing effect of GdmCl through the entire concentration range studied (0.01‐2 M), however, to a lesser extent than stabilization by NaCl. This stabilizing effect of GdmCl appears to arise from the binding of Cl − ions. Analysis of the observed changes in the stability of the ubiquitin molecule in the presence of GdmCl can be adequately described by combining the thermodynamic model of denaturant binding with Cl − binding effects.