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

Clifford R. Robinson, Yufeng Liu, Ronan O'Brien, Stephen G. Sligar, Julian M. Sturtevant

Research output: Contribution to journalArticlepeer-review

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 t( 1/4 ) 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.

Original languageEnglish (US)
Pages (from-to)961-965
Number of pages5
JournalProtein Science
Volume7
Issue number4
DOIs
StatePublished - Apr 1998

Keywords

  • Apo- and holo-cytochrome b
  • Differential scanning calorimetry
  • Thermal unfolding

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology

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