Nonspecific interaction of lac repressor with DNA: an association reaction driven by counterion release.
Nonspecific interaction of lac repressor with DNA: an association reaction driven by counterion release.
复制标题
lac 阻遏物与 DNA 的非特异性相互作用：由抗衡离子释放驱动的缔合反应。
作者：
P. Dehaseth;T. Lohman;M. Record
我们已经通过DNA-纤维素层析的定量应用研究了lac阻遏蛋白与DNA的非特异性相互作用（deHaseth，P.L.，等人（1977），Biochemistry 16（本期系列中五篇论文的第三篇））。所观察到的相互作用，KRD obsd的关联常数，是一个敏感的函数的离子浓度和pH值。应用结合理论来解释这些影响给出的结果，11 +/- 2单价离子释放的相互作用和阻遏物上的两个基团必须质子化的阻遏物结合到DNA。我们认为，大部分的离子释放的结果从DNA的阳离子的位移，并估计在此基础上，12 +/- 2磷酸参与离子与蛋白质的相互作用。离子释放驱动质子化反应和整个阻遏物-DNA相互作用。低分子量离子在阻遏物-DNA相互作用中的主要作用表明，在讨论基因表达控制机制时必须考虑离子浓度的变化。
We have investigated the nonspecific interaction of lac repressor protein with DNA by a quantitative application of DNA-cellulose chromatography (deHaseth, P.L., et al. (1977), Biochemistry 16 (third of five papers in a series in this issue)). The observed association constant for the interaction, KRD obsd, is a sensitive function of ion concentrations and pH. Application of binding theory to interpret these effects gives the results that 11 +/- 2 monovalent ions are released in the interaction and two groups on repressor must be protonated for repressor to bind to DNA. We argue that much of the ion release results from the displacement of cations from the DNA, and estimate on this basis that 12 +/- 2 phosphates are involved in ionic interactions with the protein. Ion release drives the protonation reaction and the overall repressor-DNA interaction. The major role of low molecular weight ions in the repressor-DNA interaction suggests that ion concentration changes must be considered in discussing mechanisms of control of gene expression.