MOST-USDA Joint Research Center for Food Safety & Bor Luh Food Safety Center, School of Agriculture and Biology, Shanghai Jiao Tong University, Shanghai 200240, PR China.
Microbiol Res. 2013 Mar 30;168(3):174-82. doi: 10.1016/j.micres.2012.09.003. Epub 2013 Jan 5.
Staphylococcal nuclease (here termed as Nuc1) is considered an important virulence factor and a unique marker widely used in the detection of Staphylococcus aureus. A second functional thermostable nuclease (here termed as Nuc2) in S. aureus was characterized after recombinant expression in Escherichia coli. Sequence alignment and phylogenetic analysis revealed that Nuc2 was a more conserved protein in the staphylococci group compared with Nuc1. Recombinant Nuc2 showed nuclease activity in the zymogram test and was able to degrade various types of nucleic acids. The optimal reaction temperature and pH for Nuc2 were 50 °C and pH 10, respectively. The enzymatic activity of Nuc2 was stimulated in the presence of Ca(2+) (0.05 mM), Mg(2+) (0.5mM), dithiothreitol, β-mecaptoethanol, TritonX-100, Tween-20, and urea; however, activity decreased sharply when exposed to heavy metals such as Zn(2+) and Mn(2+), and in the presence of EDTA or SDS. Nuc2 showed weaker activity, lower thermostability and different sensitivity to these chemical agents compared with Nuc1, which was consistent with differences in the sequence pattern and structure predicted. Furthermore, a nuc1 and nuc2 double deletion mutant of S. aureus and respective complementation experiments suggest a major role for nuc1 in terms of thermonuclease activity in S. aureus.
金黄色葡萄球菌核酸酶（以下简称 Nuc1）被认为是一种重要的毒力因子和独特的标记物，广泛用于金黄色葡萄球菌的检测。在大肠杆菌中重组表达后，鉴定出金黄色葡萄球菌中的第二种具有功能的耐热核酸酶（以下简称 Nuc2）。序列比对和系统发育分析表明，与 Nuc1 相比，Nuc2 是葡萄球菌属中更保守的蛋白。重组 Nuc2 在酶谱试验中显示出核酸酶活性，并能够降解各种类型的核酸。Nuc2 的最适反应温度和 pH 值分别为 50°C 和 pH 10。Nuc2 的酶活性在存在 Ca(2+)（0.05 mM）、Mg(2+)（0.5mM）、二硫苏糖醇、β-巯基乙醇、TritonX-100、Tween-20 和尿素时会受到刺激；然而，当暴露于 Zn(2+)和 Mn(2+)等重金属以及 EDTA 或 SDS 时，活性会急剧下降。与 Nuc1 相比，Nuc2 的酶活性、热稳定性和对这些化学试剂的敏感性都较弱，这与预测的序列模式和结构差异一致。此外，金黄色葡萄球菌 nuc1 和 nuc2 双缺失突变体及其互补实验表明，nuc1 在金黄色葡萄球菌热核酸酶活性方面起着主要作用。
