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首页> 外文期刊>Biochemistry >Thermodynamic analysis of the structural stability of phage 434 Cro protein.
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Thermodynamic analysis of the structural stability of phage 434 Cro protein.

机译：噬菌体434 Cro蛋白的结构稳定性的热力学分析。

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Thermodynamic parameters describing the phage 434 Cro protein have been determined by calorimetry and, independently, by far-UV circular dichroism (CD) measurements of isothermal urea denaturations and thermal denaturations at fixed urea concentrations. These equilibrium unfolding transitions are adequately described by the two-state model. The far-UV CD denaturation data yield average temperature-independent values of 0.99 +/- 0.10 kcal mol(-)(1) M(-)(1) for m and 0.98 +/- 0.05 kcal mol(-)(1) K(-)(1) for DeltaC(p)()(,U), the heat capacity change accompanying unfolding. Calorimetric data yield a temperature-independent DeltaC(p)()(,U) of 0.95 +/- 0.30 kcal mol(-)(1) K(-)(1) or a temperature-dependent value of 1.00 +/- 0.10 kcal mol(-)(1) K(-)(1) at 25 degrees C. DeltaC(p)()(,U) and m determined for 434 Cro are in accord with values predicted using known empirical correlations with structure. The free energy of unfolding is pH-dependent, and the protein is completely unfolded at pH 2.0 and 25 degrees C as judged by calorimetry or CD. The stability of 434 Cro is lower than those observed for the structurally similar N-terminal domain of the repressor of phage 434 (R1-69) or of phage lambda (lambda(6)(-)(85)), but is close to the value reported for the putative monomeric lambda Cro. Since a protein's structural stability is important in determining its intracellular stability and turnover, the stability of Cro relative to the repressor could be a key component of the regulatory circuit controlling the levels and, consequently, the functions of the two proteins in vivo.
机译：已经通过量热法确定了描述噬菌体434 Cro蛋白的热力学参数，并独立地通过在固定尿素浓度下等温尿素变性和热变性的远紫外圆二色性（CD）测量。这些平衡展开过渡由二态模型充分描述。远紫外线CD变性数据得出的平均温度独立值分别为0.99 +/- 0.10 kcal mol（-）（1）M（-）（1）和0.98 +/- 0.05 kcal mol（-）（1） K（-）（1）对于DeltaC（p）（）（，U），伴随着展开的热容变化。量热数据得出0.95 +/- 0.30 kcal mol（-）（1）K（-）（1）的温度无关的DeltaC（p）（）（，U）或1.00 +/- 0.10的温度相关的值kcal mol（-）（1）在25摄氏度时为K（-）（1）。确定434 Cro的DeltaC（p）（）（，U）和m与使用已知的结构经验关系所预测的值一致。展开的自由能是pH依赖性的，并且通过量热法或CD判断，蛋白质在pH 2.0和25摄氏度时完全展开。 434 Cro的稳定性低于噬菌体434（R1-69）或噬菌体λ（lambda（6）（-）（85））阻遏物在结构上相似的N末端结构域所观察到的稳定性，但与推定的单体λCro的报告值。由于蛋白质的结构稳定性在确定其细胞内稳定性和周转率方面很重要，因此Cro相对于阻遏物的稳定性可能是控制体内这两种蛋白质的水平以及功能的调节电路的关键组成部分。

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