Kinetic role of electrostatic interactions in the unfolding of hyperthermophilic and mesophilic rubredoxins
Kinetic role of electrostatic interactions in the unfolding of hyperthermophilic and mesophilic rubredoxins
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DOI：
10.1021/bi9721795
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发表时间：
1998-03-10
期刊：
影响因子：
2.9
通讯作者：
Chan, SI
中科院分区：
文献类型：
--
作者：
Cavagnero, S;Debe, DA;Chan, SI
研究了极端嗜热菌Pyrococcus furiosus（RdPf）和中温菌Clostridium pasteurianum（RdCp）的红曲霉素去折叠动力学的温度依赖性。结果表明，RdPf展开更慢，在所有实验可访问的温度制度，比RdCp和其他典型的嗜温蛋白。RdCp和RdPf展开的速率在pH增加到2以上时降低，并且在pH 7时显著发散。如详细的静电能计算所示，这是带负电荷的氨基酸的质子化的不同程度的结果，这导致不同的静电配置作为pH值的函数。我们提出，离子对，特别是那些被放置在关键的表面位置，可以通过温和地夹持蛋白质来发挥动力学作用，从而影响热可接近的振动简正模式的性质和数量展开更一般地说，这些模式也可能受到有利的静电配置，我们已经证明，这是直接链接到非常缓慢的展开速率的RdPf在中性pH值。即使在pH值为2，在没有任何盐桥，RdPf的展开速率远小于RdCp。这是由于目前尚未确定的结构元素的非静电性质。由于静电效应影响的展开动力学嗜温和嗜热rubredoxins，这些发现可能是一般意义的蛋白质。
The temperature dependence of the unfolding kinetics of rubredoxins from the hyperthermophile Pyrococcus furiosus (RdPf) and the mesophile Clostridium pasteurianum (RdCp) has been studied. Results show that RdPf unfolds much more slowly, under all experimentally accessible temperature regimes, than RdCp and other typical mesophilic proteins. Rates of RdCp and RdPf unfolding decrease upon increasing the pH above 2 and diverge dramatically at pH 7. As shown by detailed electrostatic energy calculations, this is the result of a differential degree of protonation of the negatively charged amino acids, which causes distinct electrostatic configurations as a function of pH. We propose that ion pairs, particularly those that are placed in key surface positions, may play a kinetic role by mildly clamping the protein and thereby influencing the nature and the number of the vibrational normal modes that are thermally accessible upon unfolding. More generally, these modes are also likely to be affected by the favorable electrostatic configurations, which we have shown to be directly linked to the extremely slow unfolding rates of RdPf at neutral pH. Even at pH 2, in the absence of any salt bridges, the unfolding rates of RdPf are much smaller than those of RdCp. This is ascribed to presently unidentified structural elements of nonelectrostatic nature. Since electrostatic effects influence the unfolding kinetics of both mesophilic and thermophilic rubredoxins, these findings may be of general significance for proteins.