Repressor of temperate mycobacteriophage LI harbors a stable C-terminal domain and binds to different asymmetric operator DNAs with variable affinity
Repressor of temperate mycobacteriophage LI harbors a stable C-terminal domain and binds to different asymmetric operator DNAs with variable affinity
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DOI：
10.1186/1743-422x-4-64
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发表时间：
2007-06-28
期刊：
影响因子：
4.8
通讯作者：
Sau, Subrata
中科院分区：
文献类型：
--
作者：
Ganguly, Tridib;Bandhu, Amitava;Sau, Subrata
背景：温和噬菌体生命周期的溶原性模式通常由一种称为“阻遏物”的蛋白质维持。温带类刺蛾的阻遏蛋白与一些对称的操纵基因DNA结合，以调节它们的基因表达。相反，温和型分枝杆菌噬菌体和其他一些噬菌体的阻遏物分子与多个不对称操纵基因DNA结合。结果：利用高度纯化的温和型分枝杆菌噬菌体LI的阻遏物（repressor，CI），我们证明了LI CI含有一个N-末端结构域（NTD）和一个C-末端结构域（CTD），它们被一个小的铰链区分隔开。有趣的是，CTD在25 ℃时比NTD更紧凑。CTD和CI在30 ℃下都含有大量的α-螺旋，但在42 ℃下部分解折叠。在接近200 nM的浓度下，两种蛋白质在溶液中形成可观量的二聚体。另外的研究表明，CI在25 ℃下以可变的亲和力结合LI的O-64和OL型不对称操作子。有趣的是，阻遏子-操纵子的相互作用在42 ℃时会受到很大的影响. CI的构象变化是最有可能负责其在42摄氏度的操作符结合亲和力降低。结论：由分枝杆菌噬菌体编码的阻遏蛋白显着不同的阻遏蛋白。在功能水平上，它们与相关的神经元几乎相同，但在结构水平上，它们几乎相同。
Background: Lysogenic mode of life cycle of a temperate bacteriophage is generally maintained by a protein called 'repressor'. Repressor proteins of temperate lambdoid phages bind to a few symmetric operator DNAs in order to regulate their gene expression. In contrast, repressor molecules of temperate mycobacteriophages and some other phages bind to multiple asymmetric operator DNAs. Very little is known at present about the structure- function relationship of any mycobacteriophage repressor.Results: Using highly purified repressor (CI) of temperate mycobacteriophage LI, we have demonstrated here that LI CI harbors an N-terminal domain (NTD) and a C- terminal domain (CTD) which are separated by a small hinge region. Interestingly, CTD is more compact than NTD at 25 degrees C. Both CTD and CI contain significant amount of alpha-helix at 30 degrees C but unfold partly at 42 degrees C. At nearly 200 nM concentration, both proteins form appreciable amount of dimers in solution. Additional studies reveal that CI binds to O-64 and OL types of asymmetric operators of LI with variable affinity at 25 degrees C. Interestingly, repressor - operator interaction is affected drastically at 42 degrees C. The conformational change of CI is most possibly responsible for its reduced operator binding affinity at 42 degrees C.Conclusion: Repressors encoded by mycobacteriophages differ significantly from the repressor proteins of. and related phages at functional level but at structural level they are nearly similar.