Firefly luciferase as a bioluminescent enzyme has many applications in various fields from scientific research to commercial goals. This enzyme is relatively unstable with low functional capacity due to rapid inactivation in physiological temperature, low in vitro stability and high susceptibility to proteolytic degradation. Based on previous studies, two regions 206-220 and 329-341 on N-domain of Photinus pyralis luciferase are known accessible and flexible. Flexible regions may lead to protein instability. Here, the effect of mutation at positively charged residues Lys(K)329 and Arg(R)330 on the stability of luciferase was studied. Furthermore, the role of these mutations on the structure and function was evaluated. Introducing of these point mutations did not affect the orientation of critical residues in bioluminescence color determination. The kinetic studies showed that thermostability and Km value for luciferin in both mutants were decreased as compared to wild type. However, optimum pH and optimum temperature showed no significant changes in both mutants. Moreover, the structural data revealed an increase in tryptophan fluorescence intensity and secondary structure content for R330Q in compared with wild type, while intrinsic fluorescence and far-UV CD intensity in K329I mutant was decreased.

中文翻译：

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萤火虫荧光素酶柔性区域带正电荷残基（K329 和 R330）突变对结构和动力学特性的影响

萤火虫荧光素酶作为一种生物发光酶在从科学研究到商业目标的各个领域都有许多应用。由于在生理温度下快速失活、体外稳定性低和对蛋白水解降解的高度敏感性，该酶相对不稳定，功能能力低。根据先前的研究，已知 Photinus pyralis 荧光素酶 N 域上的两个区域 206-220 和 329-341 是可访问且灵活的。柔性区域可能导致蛋白质不稳定。在此，研究了带正电荷残基 Lys(K)329 和 Arg(R)330 处的突变对荧光素酶稳定性的影响。此外，评估了这些突变对结构和功能的作用。引入这些点突变不会影响生物发光颜色测定中关键残基的方向。动力学研究表明，与野生型相比，两种突变体中荧光素的热稳定性和 Km 值均降低。然而，最适 pH 值和最适温度在两个突变体中都没有显着变化。此外，结构数据显示，与野生型相比，R330Q 的色氨酸荧光强度和二级结构含量增加，而 K329I 突变体的固有荧光和远紫外 CD 强度降低。