A differential scanning calorimetric study of the thermal unfolding of apo‐ and holo‐cytochrome b562
Open Access
- 1 April 1998
- journal article
- research article
- Published by Wiley in Protein Science
- Vol. 7 (4) , 961-965
- https://doi.org/10.1002/pro.5560070413
Abstract
Cytochrome b562 is a four-helix-bundle protein containing a non-covalently bound b-type heme prosthetic group. In the absence of heme, cytochrome b562 remains highly structured under native conditions. Here we report thermodynamic data for the thermal denaturation of the holo- and apoproteins as determined by differential scanning calorimetry. Thermal denaturation of holocytochrome b562 is a highly reversible process, and unexpectedly does not involve dissociation of the heme prosthetic group. Thermal denaturation of the corresponding apoprotein, with the heme group chemically removed, remains a cooperative, reversible process. Apocytochrome b562 is substantially destabilized relative to the holoprotein: the t1/2 is more than ten degrees lower, and enthalpy and heat capacity changes are about one-half of the holoprotein values. However, the energetic parameters of apocytochrome b562denaturation are within the range of observed values for small proteins.Keywords
Funding Information
- JMS (GM-04725)
- SGS (GM-31756, GM-33775)
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