Department of Physics, Indiana University-Purdue University Indianapolis, Indianapolis, IN 46202, USA.
J Biomol Struct Dyn. 2012;30(6):628-37. doi: 10.1080/07391102.2012.689696. Epub 2012 Jun 26.
Thermodynamic stability of a protein at elevated temperatures is a key factor for thermostable enzymes to catalyze their specific reactions. Yet our understanding of biological determinants of thermostability is far from complete. Many different atomistic factors have been suggested as possible means for such proteins to preserve their activity at high temperatures. Among these factors are specific local interatomic interactions or enrichment of specific amino acid types. The case of glycosyl hydrolase family endoglucanase of Trichoderma reesei defies current hypotheses for thermostability because a single mutation far from the active site (A35 V) converts this mesostable protein into a thermostable protein without significant change in the protein structure. This substantial change in enzymatic activity cannot be explained on the basis of local intramolecular interactions alone. Here we present a more global view of the induced thermostability and show that the A35 V mutation affects the underlying structural rigidity of the whole protein via a number of long-range, non-local interactions. Our analysis of this structure reveals a precisely tuned, rigid network of atomic interactions. This cooperative, allosteric effect promotes the transformation of this mesostable protein into a thermostable one.
在高温下，蛋白质的热力学稳定性是热稳定酶催化其特定反应的关键因素。然而，我们对热稳定性的生物学决定因素的理解还远远不够。许多不同的原子因素被认为是蛋白质在高温下保持活性的可能手段。这些因素包括特定的局部原子间相互作用或特定氨基酸类型的富集。里氏木霉内切葡聚糖酶糖基水解酶家族的情况违反了目前关于热稳定性的假设，因为远离活性位点的单个突变（A35V）将这种介稳蛋白转化为热稳蛋白，而蛋白质结构没有明显变化。这种酶活性的巨大变化不能仅仅基于局部分子内相互作用来解释。在这里，我们提出了一个更全局的观点，表明 A35V 突变通过许多远程、非局部相互作用影响整个蛋白质的基础结构刚性。我们对该结构的分析揭示了一个精确调整的、刚性的原子相互作用网络。这种协同的变构效应促进了这种介稳蛋白向热稳蛋白的转化。
