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. 1998 Apr;7(4):961–965. doi: 10.1002/pro.5560070413

A differential scanning calorimetric study of the thermal unfolding of apo- and holo-cytochrome b562.

C R Robinson 1, Y Liu 1, R O'Brien 1, S G Sligar 1, J M Sturtevant 1
PMCID: PMC2143982  PMID: 9568902

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 b562 denaturation are within the range of observed values for small proteins.

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Selected References

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