Energetic basis on interactions between ferredoxin and ferredoxin NADP+ reductase at varying physiological conditions.
Energetic basis on interactions between ferredoxin and ferredoxin NADP+ reductase at varying physiological conditions.
复制标题
不同生理条件下铁氧还蛋白和铁氧还蛋白 NADP 还原酶之间相互作用的能量基础。
DOI：
10.1016/j.bbrc.2016.11.132
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发表时间：
2016
期刊：
影响因子：
--
通讯作者：
Y.H.
中科院分区：
文献类型：
--
作者：
Kinoshita;M.;Kim;J.Y.;S.;Lin;Y.;Hun Mok K.;Kataoka;Y.;Ishimori;K.;Markova;N.;Kurisu;G.;Hase;T.;Lee;Y.H.
尽管有大量的研究来表征铁氧还蛋白（Fd）：铁氧还蛋白NADP+还原酶（FNR）在有限条件下的相互作用，但关于这些蛋白在接近生理条件下如何相互作用及其与FNR活性的联系的详细的能量研究仍然缺乏。本文使用等温滴定量热法（ITC）在不同的pH（6.0和8.0）、NaCl浓度（0-200 mM）和温度（19-28 °C）下模拟叶绿体中的生理条件进行了系统的Fd：FNR结合热力学。这种能量成本得到了有利的熵变的补偿，并被构象熵和水合熵所平衡。在NaCl浓度和pH值的增加削弱了蛋白间的亲和力，由于有利的熵变的贡献较小，无论能量增益从焓变化，这表明熵驱动络合和调制的亲和力。温度对结合热力学的影响远小于pH和NaCl。NaCl浓度和pH值依赖的焓和热容的变化提供了线索不同的结合模式。此外，在哈蒙德的假设为基础的能源景观的焓水平的下降暗示的动力学优势FNR activity.All这些能量的相互作用得到了全面的证明，驱动力与熵补偿，这可能是一个能量缓冲器对外部应力。我们建议，在pH 6.0的高亲和力可能有利于保护Fd和FNR的蛋白水解在休息状态，和适度的亲和力在pH 8.0和适当的NaCl浓度较小的吸热焓变可能有助于增加FNR活性。
In spite of a number of studies to characterize ferredoxin (Fd):ferredoxin NADP+reductase (FNR) interactions at limited conditions, detailed energetic investigation on how these proteins interact under near physiological conditions and its linkage to FNR activity are still lacking.We herein performed systematic Fd:FNR binding thermodynamics using isothermal titration calorimetry (ITC) at distinct pH (6.0 and 8.0), NaCl concentrations (0–200 mM), and temperatures (19–28 °C) for mimicking physiological conditions in chloroplasts.Energetically unfavorable endothermic enthalpy changes were accompanied by Fd:FNR complexation at all conditions. This energetic cost was compensated by favorable entropy changes, balanced by conformational and hydrational entropy. Increases in the NaCl concentration and pH weakened interprotein affinity due to the less contribution of favorable entropy change regardless of energetic gains from enthalpy changes, suggesting that entropy drove complexation and modulated affinity. Effects of temperature on binding thermodynamics were much smaller than those of pH and NaCl. NaCl concentration and pH-dependent enthalpy and heat capacity changes provided clues for distinct binding modes. Moreover, decreases in the enthalpy level in the Hammond's postulate-based energy landscape implicated kinetic advantages for FNR activity.All these energetic interplays were comprehensively demonstrated by the driving force plot with the enthalpy-entropy compensation which may serve as an energetic buffer against outer stresses. We propose that high affinity at pH 6.0 may be beneficial for protection from proteolysis of Fd and FNR in rest states, and moderate affinity at pH 8.0 and proper NaCl concentrations with smaller endothermic enthalpy changes may contribute to increase FNR activity.