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首页> 外文期刊>Journal of Molecular Biology >Differential Affinity and Cooperativity Functions of the Amino-terminal 70 Residues of lambda Integrase.
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Differential Affinity and Cooperativity Functions of the Amino-terminal 70 Residues of lambda Integrase.

机译：Lambda整合酶的氨基末端70个残基的差分亲和力和协同功能。

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摘要

The site-specific recombinase (Int) of bacteriophage lambda is a heterobivalent DNA-binding protein that binds two different classes of DNA-binding sites within its recombination target sites. The several functions of Int are apportioned between a large carboxy-terminal domain that cleaves and ligates DNA at each of its four "core-type" DNA-binding sites and a small amino-terminal domain, whose primary function is binding to each of its five "arm-type" DNA sites, which are distant from the core region. Int bridges between the two classes of binding sites are facilitated by accessory DNA-bending proteins that along with Int comprise higher-order recombinogenic complexes. We show here that although the 64 amino-terminal residues of Int bind efficiently to a single arm site, this protein cannot form doubly bound complexes on adjacent arm sites. However, 1-70 Int does show the same cooperative binding to adjacent arm sites as the full length protein. We also found that 1-70 Int specifies cooperative interactions with the accessory protein Xis when the two are bound to their adjacent cognate sites P2 and X1, respectively. To complement the finding that these two amino-terminal domain functions (along with arm DNA binding) are all specified by residues 1-70, we determined that Thr75 is the first residue of the minimal carboxy-terminal domain, thereby identifying a specific interdomain linker region. We have measured the affinity constants for Int binding to each of the five arm sites and the cooperativity factors for Int binding to the two pairs of adjacent arm sites, and we have identified several DNA structural features that contribute to the observed patterns of Int binding to arm sites. Taken together, the results highlight several interesting features of arm DNA binding that invite speculation about additional levels of complexity in the regulation of lambda site-specific recombination.
机译：噬菌体λ的位点特异性重组酶（Int）是一种异双价DNA结合蛋白，可在其重组靶位点内结合两种不同类型的DNA结合位点。 Int的几种功能分配在一个较大的羧基末端结构域和一个较小的氨基末端结构域之间，该羧基末端结构域在其四个“核心型” DNA结合位点的每一个处切割并连接DNA，而氨基末端结构域的主要功能是与其五个“臂型” DNA位点，它们远离核心区域。两类结合位点之间的Int桥可通过辅助DNA弯曲蛋白（与Int一起包含更高阶的重组原复合物）来促进。我们在这里显示，尽管Int的64个氨基末端残基有效地结合到单个臂位，但该蛋白质不能在相邻臂位上形成双重结合的复合物。但是，1-70 Int确实显示出与全长蛋白质相同的对相邻臂位的协同结合。我们还发现，当二者分别结合到它们相邻的同源位点P2和X1时，1-70 Int指定与辅助蛋白Xis的协同相互作用。为了补充这两个氨基末端结构域功能（连同臂DNA结合）全部由残基1-70指定的发现，我们确定Thr75是最小羧基末端结构域的第一个残基，从而鉴定了特定的域间连接子地区。我们已经测量了Int与五个臂位的每个结合的亲和常数和Int与两对相邻臂位的结合的协同作用因子，并且确定了几个DNA结构特征，这些特征有助于观察到的Int与两个臂位结合的模式。手臂站点。两者合计，结果突出了手臂DNA绑定的几个有趣的功能，这引发了人们对lambda位点特异性重组调控中复杂性的额外水平的猜测。

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