On the advantage of being a dimer, a case study using the dimeric Serratia nuclease and the monomeric nuclease from Anabaena sp. strain PCC 71209
On the advantage of being a dimer, a case study using the dimeric Serratia nuclease and the monomeric nuclease from Anabaena sp. strain PCC 71209
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DOI：
10.1074/jbc.274.2.825
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发表时间：
1999-01-08
影响因子：
4.8
通讯作者：
Pingoud, A
中科院分区：
文献类型：
--
作者：
Franke, I;Meiss, G;Pingoud, A
来自粘质沙雷氏菌和鱼腥藻的胞外核酸内切酶是非特异性核酸内切酶家族的成员。与单体鱼腥藻核酸酶相比，沙雷氏菌核酸酶是两个相同亚基的二聚体。为了发现沙雷氏菌核酸酶的两个活性位点是否彼此独立地起作用以及作为该酶的二聚体的优点可能是什么，我们产生了（i）其中两个亚基交联的二聚体，（ii）由野生型和也交联的失活突变亚基组成的异二聚体，和（iii）不能二聚化的单体变体，单体H184 R变体和交联的S140 C变体表现出与野生型酶相同的活性，而具有一个失活亚基的交联异二聚体仅表现出野生型酶活性的一半，证明了沙雷氏菌属核酸酶的两个亚基的功能独立性。另一方面，在低酶和底物浓度下，沙雷氏菌属核酸酶的二聚体形式比单体形式或单体鱼腥藻属核酸酶在切割多核苷酸而不是寡核苷酸方面相对更有活性，其与沙雷氏菌核酸酶的二聚体形式与高分子量DNA形成大的酶-底物网络并以进行性方式切割多核苷酸的能力相关，我们的结论是，在粘质沙雷氏菌的自然栖息地，营养物质的供应可能成为生长限制，二聚核酸酶可以实现其营养比单体酶更有效地发挥作用。
The extracellular endonucleases from Serratia marcescens and Anabaena sp. are members of a family of nonspecific endonucleases. In contrast to the monomeric Anabaena nuclease, the Serratia nuclease is a dimer of two identical subunits, To find out whether the two active sites of the Serratia nuclease function independently of each other and what the advantage of being a dimer for this enzyme might be, we produced (i) dimers in which the two subunits were cross-linked, (ii) heterodimers consisting of a wild type and an inactive mutant subunit which were also cross-linked, and (iii) monomeric variants which are unable to dimerize, The monomeric H184R variant and the cross-linked S140C variant exhibit the same activity as the wild type enzyme, while the cross-linked heterodimer with one inactive subunit shows only half of the activity of the wild type enzyme, demonstrating functional independence of the two subunits of the Serratia nuclease, On the other hand at low enzyme and substrate concentrations dimeric forms of the Serratia nuclease are relatively more active than monomeric forms or the monomeric Anabaena nuclease in cleaving polynucleotides, not, however, oligonucleotides, which is correlated with the ability of dimeric forms of the Serratia nuclease to form large enzyme-substrate networks with high molecular weight DNA and to cleave polynucleotides in a processive manner, We conclude that in the natural habitat of Serratia marcescens where the supply of nutrients may become growth limiting the dimeric nuclease can fulfil its nutritive function more efficiently than a monomeric enzyme.