Hochschild A, Douhan J, Ptashne M
Cell. 1986 Dec 5;47(5):807-16. doi: 10.1016/0092-8674(86)90523-4.
Although lambda repressor and lambda Cro bind to the same six operators on the phage chromosome, the fine specificities of the two proteins differ: repressor binds more tightly to OR1 than to OR3, and vice versa for Cro. In this paper, we change base pairs in the operators and amino acids in the proteins to analyze the basis for these preferences. We find that these preferences are determined by residues 5 and 6 of the recognition helices of the two proteins and by the amino-terminal arm, in the case of repressor. We also find that the most important base pairs in the operator which enable repressor and Cro to discriminate between OR1 and OR3 are position 3 (for Cro) and positions 5 and 8 (for repressor). These and previous results show how repressor and Cro recognize and distinguish between two related operator sequences.
尽管λ阻遏蛋白和λ Cro蛋白结合噬菌体染色体上相同的六个操纵基因，但这两种蛋白质的精细特异性有所不同：阻遏蛋白与OR1的结合比与OR3更紧密，而Cro则相反。在本文中，我们改变操纵基因中的碱基对和蛋白质中的氨基酸，以分析这些偏好的基础。我们发现，这些偏好是由这两种蛋白质识别螺旋的第5和第6位残基以及阻遏蛋白的氨基末端臂决定的。我们还发现，操纵基因中使阻遏蛋白和Cro能够区分OR1和OR3的最重要碱基对，对于Cro来说是第3位，对于阻遏蛋白来说是第5和第8位。这些以及之前的结果表明了阻遏蛋白和Cro如何识别并区分两个相关的操纵基因序列。
