NMR study of the alkaline isomerization of ferricytochrome c

FEBS Letters

Dixon, Dabney White¹  Hong, Xiaole¹ 

[1] Department of Chemistry and Laboratory for Microbial and Biochemical Sciences, Georgia State University, Atlanta, GA 30303, USA

关键词: Cytochrome c;    Isomerization;    alkaline;    Kinetics;    Activation parameters;   

DOI  :  10.1016/0014-5793(89)80262-5

学科分类：生物化学/生物物理

来源: John Wiley & Sons Ltd.

【 摘 要 】

The pH-induced isomerization of horse heart cytochrome c has been studied by ¹H NMR. We find that the transition occurring in D₂O with a pK _a measured as 9.5±0.1 is from the native species to a mixture of two basic forms which have very similar NMR spectra. The heme methyl peaks of these two forms have been assigned by 2D exchange NMR. The forward rate constant (native to alkaline cytochrome c) has a value of 4.0±0.6 s⁻¹ at 27°C and is independent of pH; the reverse rate constant is pH-dependent. The activation parameters are ΔH ^‡ = 12.8±0.8 kcal·mol¹, ΔS ^‡ = − 12.9±2.0 e.u. for the forward reaction and ΔH ^‡ = 6.0±0.3 kcal·mol⁻¹, ΔS ^‡ = − 35.1±1.3 e.u. for the reverse reaction (pH*=9.28). ΔH° and ΔS° for the isomerization are 6.7±0.6 kcal·mol⁻¹ and 21.9±1.0 e.u., respectively.

【 授权许可】

Unknown