Flap endonuclease is a structure-specific nuclease which cleaves 5'-flap of bifurcated DNA substrates. Genome sequence of Thermococcus kodakarensis harbors an open reading frame, Tk1281, exhibiting high homology with archaeal flap endonucleases 1. The corresponding gene was cloned and expressed in Escherichia coli, and the gene product was purified to apparent homogeneity. Tk1281 was a monomer of 38 kDa and catalyzed the cleavage of 5'-flap from double-stranded DNA substrate containing single-stranded DNA flap. The highest cleavage activity was observed at 80 °C and pH 7.5. Under optimal conditions, Tk1281 exhibited apparent Vmax and Km values of 278 nmol/min/mg and 37 μM, respectively, against a 54-nucleotide double-stranded substrate containing a single-stranded 5'-flap of 27 nucleotides. A unique feature of Tk1281 is its highest activation in the presence of Co2+ and no activation with Mn2+. To the best of our knowledge, this is the first cloning and characterization of a flap endonuclease from the genus Thermococcus.

中文翻译：

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Tk1281基因的克隆和鉴定，该蛋白是来自柯达卡热球菌的皮瓣内切核酸酶1。

瓣内切核酸酶是一种结构特异性核酸酶，其切割分支的DNA底物的5'-瓣。柯达热球菌的基因组序列带有一个开放阅读框Tk1281，与古细菌瓣内切核酸酶1具有高度同源性。将相应的基因克隆并在大肠杆菌中表达，并将该基因产物纯化至明显的同质性。Tk1281是38 kDa的单体，可催化从含有单链DNA瓣的双链DNA底物上裂解5'-瓣。在80°C和pH 7.5下观察到最高的裂解活性。在最佳条件下，Tk1281的表观Vmax和Km值分别为278 nmol / min / mg和37μM，相对于含有27个核苷酸的5'-flap的54核苷酸双链底物。Tk1281的独特功能是在Co2 +存在下具有最高的活化度，而Mn2 +则无活化作用。据我们所知，这是Thermococcus属的皮瓣内切核酸酶的首次克隆和鉴定。