Thermal unfolding of monomeric Ca(II),Mg(II)‐ATPase from sarcoplasmic reticulum of rabbit skeletal muscle

FEBS Letters

Moller, Jesper V.¹  Merino, Jaime M.²  Gutiérrez-Merino, Carlos² 

[1]Institute de Biophysics, University of Aarhus, DK-8000 Aarhus C, Denmark

[2]Departamento de Bioquímica y Biologia Molecular, Facultad de Ciencias, Universidad de Extremadura, 06080-Badajoz, Spain

关键词: Ca2+;    Mg2+-ATPase;    Sarcoplasmic reticulum;    Monomeric ATPase;    Differential scanning calorimetry;    Ca2+;    Mg2+-ADP;    SR;    sarcoplasmic reticulum;    ATPase;    Ca(II) + Mg(II)- ATPase (EC 3.6.1.38);    C12E8;    octaethylene glycol dodecyl ether;    I.U.;    micromoles of product per minute per milligram of protein;    DSC;    differential scanning calorimetry;    ΔH;    enthalpy of denaturation process;    T m;    critical temperature midpoint of denaturation process;   

DOI  :  10.1016/0014-5793(94)80309-9

学科分类：生物化学/生物物理

来源: John Wiley & Sons Ltd.

【 摘 要 】

The thermal unfolding of monomeric and delipidated Ca²⁺-ATPase, solubilized in C₁₂E₈, can be appropriately described as a non-two-state irreversible denaturation, with only one endothermic peak. In the Ca²⁺ concentration range (0–0.5 mM) which stimulates the ATPase activity of solubilized monomeric ATPase, Ca²⁺ shifts the critical temperature midpoint of the denaturation process (T _m) from 42 to 50°C without segregation of the endothermic peak into two separate components. Because 20 mM Mg²⁺ only shifts the T _m from 42 to 44°C, we conclude that the effect of Ca²⁺ upon the T _m is likely to be due to binding to the high affinity Ca²⁺ sites in the ATPase. The effect of Ca²⁺ upon the enthalpy of denaturation is biphasic, suggesting the presence of low affinity Ca²⁺ sites (K _0.5 in the millimolar range) in monomeric and solubilized ATPase.

【 授权许可】

Unknown