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Conformational stability of bovine holo and apo adrenodoxin — A scanning calorimetric study
Author(s) -
Burova Tatjana V.,
Bernhardt Rita,
Pfeil Wolfgang
Publication year - 1995
Publication title -
protein science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.353
H-Index - 175
eISSN - 1469-896X
pISSN - 0961-8368
DOI - 10.1002/pro.5560040510
Subject(s) - adrenodoxin , chemistry , enthalpy , denaturation (fissile materials) , circular dichroism , crystallography , differential scanning calorimetry , thermal stability , calorimetry , proteolysis , biochemistry , organic chemistry , thermodynamics , nuclear chemistry , physics , enzyme , cytochrome
Holo and apo adrenodoxin were studied by differential scanning calorimetry, absorption spectroscopy, limited proteolysis, and size‐exclusion chromatography. To determine the conformational stability of adrenodoxin, a method was found that prevents the irreversible destruction of the iron‐sulfur center. The approach makes use of a buffer solution that contains sodium sulfide and mercaptoethanol. The thermal transition of adrenodoxin takes place at T trs = 46–57 °C, depending on the Na 2 S concentration with a denaturation enthalpy of Δ H = 300–380 kJ/mol. From Δ H versus T trs a heat capacity change was determined as Δ C p — 7.5 ± 1.2 kJ/mol/K. The apo protein is less stable than the holo protein as judged by the lower denaturation enthalpy (Δ H = 93 ± 14 kJ/mol at T trs = 37.4 ± 3.3 °C) and the higher proteolytic susceptibility. The importance of the iron‐sulfur cluster for the conformational stability of adrenodoxin and some conditions for refolding of the thermally denatured protein are discussed.