Coupled energetics of λ cro repressor self-assembly and site-specific DNA operator binding II:: Cooperative interactions of cro dimers
Coupled energetics of λ cro repressor self-assembly and site-specific DNA operator binding II:: Cooperative interactions of cro dimers
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DOI：
10.1006/jmbi.2000.4050
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发表时间：
2000-09-22
影响因子：
5.6
通讯作者：
Ackers, GK
中科院分区：
文献类型：
--
作者：
Darling, PJ;Holt, JM;Ackers, GK
噬菌体lambda依赖于cI和交叉抑制因子的相互作用，它们自组装并结合噬菌体基因组的两个操作符（O-R和O-L）来控制溶原到裂解的开关。虽然已经详细研究了cI的自组装和OR结合，但要更全面地了解噬菌体lambda的基因调控，还需要详细了解交叉抑制因子的作用，因为它在O-R位点进行二聚体和结合。由于二聚化和算子结合是耦合过程，因此要充分阐明该系统中的调控能量学，需要确定二聚化和协同结合的平衡常数。作为这些结合研究的前奏，已经测量了cross的二聚化常数。在这里，交叉结合O-R的能量学，是评估使用定量dna足迹滴定技术。同时分析了野生型和修饰型O-R位点组合的结合数据，并结合二聚化能量，获得了三个O-R位点的内在和合作DNA结合能。二聚体与O(R)3的结合最强，其次是O(R)1，最后是O(R)2。邻接结合抑制因子表现出正协同性，范围为-0.6 ~ -1.0 kcal/mol。在基因调控的动态模型框架中讨论了这些新解决的能量学的含义。这种对cross阻遏物dna结合特性的描述为该系统可以探索其他更复杂的调控元件（如ci - cross协同性）奠定了基础。(C) 2000年学术出版社。
The bacteriophage lambda relies on interactions of the cI and cro repressors which self assemble and bind the two operators (O-R and O-L) of the phage genome to control the lysogenic to lytic switch. While the self assembly and OR binding of cI have been investigated in detail, a more complete understanding of gene regulation by phage lambda also requires detailed knowledge of the role of cro repressor as it dimerizes and binds at O-R sites. Since dimerization and operator binding are coupled processes, a full elucidation of the regulatory energetics in this system requires that the equilibrium constants for dimerization and cooperative binding be determined. The dimerization constant for cro has been measured as a prelude to these binding studies. Here, the energetics of cro binding to O-R, are evaluated using quantitative DNaseI footprint titration techniques. Binding data for wild-type and modified O-R site combinations have been simultaneously analyzed in concert with the dimerization energetics to obtain both the intrinsic and cooperative DNA binding energies for cro with the three O-R ,sites. Binding of cro dimers is strongest to O(R)3, then O(R)1 and lastly, O(R)2. Adjacently bound repressors exhibit positive cooperativity ranging from -0.6 to -1.0 kcal/mol. Implications of these, newly resolved, energetics are discussed in the framework of a dynamic model for gene regulation. This characterization of the DNA-binding properties of cro repressor establishes the foundation on which the system can be explored for other, more complex, regulatory elements such as cI-cro cooperativity. (C) 2000 Academic Press.