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Analysis of the pH-dependent thermodynamic stability, local motions, and microsecond folding kinetics of carbonmonoxycytochrome c.
- Source :
-
Archives of Biochemistry & Biophysics . Sep2016, Vol. 606, p16-25. 10p. - Publication Year :
- 2016
-
Abstract
- This paper analyzes the effect of pH on thermodynamic stability, low-frequency local motions and microsecond folding kinetics of carbonmonoxycytochrome c (Cyt-CO) all across the alkaline pH-unfolding transition of protein. Thermodynamic analysis of urea-induced unfolding transitions of Cyt-CO measured between pH 6 and pH 11.9 reveals that Cyt-CO is maximally stable at pH∼9.5. Dilution of unfolded Cyt-CO into refolding medium forms a native-like compact state (NCO-state), where Fe 2+ −CO interaction persists. Kinetic and thermodynamic parameters measured for slow thermally-driven CO dissociation (NCO→N+CO) and association (N+CO→NCO) reactions between pH 6.5 and pH 13 reveal that the thermal-motions of M80-containing Ω-loop are decreased in subdenaturing limit of alkaline pH. Laser photolysis of Fe 2+ -CO bond in NCO-state triggers the microsecond folding (NCO→N). The microsecond kinetics measured all across the alkaline pH-unfolding transition of Cyt-CO produce rate rollover in the refolding limb of chevron plot, which suggests a glass transition of NCO en route to N. Between pH 7 and pH 11.9, the natural logarithm of the microsecond folding rate varies by < 1.5 units while the natural logarithm of apparent equilibrium constant varies by 11.8 units. This finding indicates that the pH-dependent ionic-interactions greatly affect the global stability of protein but have very small effect on folding kinetics. [ABSTRACT FROM AUTHOR]
- Subjects :
- *THERMODYNAMICS
*CYTOCHROMES
*DENATURATION of proteins
*LOGARITHMS
*PROTEIN kinases
Subjects
Details
- Language :
- English
- ISSN :
- 00039861
- Volume :
- 606
- Database :
- Academic Search Index
- Journal :
- Archives of Biochemistry & Biophysics
- Publication Type :
- Academic Journal
- Accession number :
- 117555714
- Full Text :
- https://doi.org/10.1016/j.abb.2016.07.010