Calorimetric studies of the thermal denaturation of cytochrome c peroxidase

Journal Article · Tue Apr 05 00:00:00 EDT 1988 · Biochemistry; (United States)

DOI:https://doi.org/10.1021/bi00407a035· OSTI ID:5293085

Kresheck, G C; Erman, J E

Two endotherms are observed by differential scanning calorimetry during the thermal denaturation of cytochrome c peroxidase at pH 7.0. The transition midpoint temperatures (t/sub m/) were 43.9 +- 1.4 and 63.3 +- 1.6 /sup 0/C, independent of concentration. The two endotherms were observed at all pH values between 4 and 8, with the transition temperatures varying with pH. Precipitation was observed between pH 4 and 6, and only qualitative data are presented for this region. The thermal unfolding of cytochrome c peroxidase was sensitive to the presence and ligation state of the heme. Only a single endotherm was observed for the unfolding of the apoprotein, and this transition was similar to the high-temperature transition in the holoenzyme. Addition of KCN to the holoenzyme increases the midpoint of the high-temperature transition whereas the low-temperature transition was increased upon addition of KF. Binding of the natural substrate ferricytochrome c to the enzyme increases the low-temperature transition by 4.8 +- 1.3 /sup 0/C but has no effect on the high-temperature transition at pH 7. The presence of cytochrome c peroxidase decreases the stability of cytochrome c, and both proteins appear to unfold simultaneously. The results are discussed in terms of the two domains evident in the X-ray crystallographic structure of cytochrome c peroxidase

• Research Organization: Northern Illinois Univ., DeKalb (USA)
• OSTI ID: 5293085
• Journal Information: Biochemistry; (United States), Vol. 27:7
• Country of Publication: United States
• Language: English

Related Subjects

62 RADIOLOGY AND NUCLEAR MEDICINE
63 RADIATION, THERMAL, AND OTHER ENVIRON. POLLUTANT EFFECTS ON LIVING ORGS. AND BIOL. MAT.
PEROXIDASES
PROTEIN DENATURATION
TEMPERATURE EFFECTS
X-RAY DIFFRACTION
CALORIMETRY
CRYSTALLOGRAPHY
CYTOCHROMES
PH VALUE
COHERENT SCATTERING
DIFFRACTION
ENZYMES
ORGANIC COMPOUNDS
OXIDOREDUCTASES
PIGMENTS
PROTEINS
SCATTERING
550602* - Medicine- External Radiation in Diagnostics- (1980-)
560200 - Thermal Effects