Determination of the pK for the Acid-Induced Denaturation of Ferrocytochrome c
- 1 March 2004
- journal article
- research article
- Published by American Chemical Society (ACS) in Biochemistry
- Vol. 43 (12) , 3564-3569
- https://doi.org/10.1021/bi036011x
Abstract
Optical absorption spectroscopy was used to characterize the acid-induced conformational transition of horse heart ferrocytochrome c in the presence of urea. By using linear extrapolation to zero denaturant concentration, an apparent pK value for denaturation was found to be 0.86 +/- 0.07 at 25 degrees C. Visible absorption spectra in the presence of high urea concentration indicate that the dominant population is a high-spin, five-coordinate form under acidic conditions. Ferricytochrome c, used as a model reference system, shows a linear dependence of pK values versus urea concentration in the range from 0 to 4.1 M. Our data also indicate that even at a pH below 2 the iron-sulfur bond in ferrocytochrome c is present.Keywords
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