Base sequence‐specific interactions of operator DNA fragments with the lambda‐cro repressor coupled with changes in their conformations.
Base sequence‐specific interactions of operator DNA fragments with the lambda‐cro repressor coupled with changes in their conformations.
复制标题
操纵子 DNA 片段与 lambda-cro 阻遏物的碱基序列特异性相互作用及其构象的变化。
作者：
S. J. Lee;M. Shirakawa;H. Akutsu;Y. Kyōgoku;M. Shiraishi;K. Kitano;M. Shin;E. Ohtsuka;M. Ikehara
使用质子核磁共振研究了操纵基因DNA与λ-cro阻遏蛋白的相互作用机制。照片CIDNP制备了三种DNA双链体，即λ-OR 3 17-mer、phi 80-OR 2 19-mer和CRP结合位点22-mer，并将其与λ-cro的复合物的所有亚氨基质子共振分配给单个碱基对。通过监测DNA片段和λ-cro的指定信号，发现在λ-cro与λ-OR 3的复合物中，cro二聚体的两个亚基分别与OR 3的左半部分和右半部分结合，并且双齿结合诱导17-mer中间的结构畸变。λ-cro本身也经历构象变化，包括二聚体形式的松弛。在lambda‐cro与phi 80‐ OR 2的复合物中，其具有与lambda‐ OR 3共同的6 bp序列，cro二聚体的一个亚基似乎特异性地结合到共同部分。然而，cro二聚体只有轻微的构象变化。在CRP结合位点22-mer和λ-cro的混合物中，观察到它们之间没有任何构象变化的软接触。
The mechanism of interaction of the operator DNA with the lambda‐cro repressor protein was investigated using proton n.m.r. and photo CIDNP. Three kinds of DNA duplexes, the lambda‐OR3 17‐mer, phi80‐OR2 19‐mer and CRP binding site 22‐mer, were prepared, and all of their imino proton resonances of the complexes with lambda‐cro were assigned to individual base pairs. By monitoring the assigned signals of the DNA fragments and lambda‐cro, it was found that in the complex of lambda‐cro with lambda‐OR3, two subunits of the cro dimer bind to the right and left halves of the OR3, respectively, and the bidentate binding induces a structural distortion in the middle of the 17‐mer. lambda‐cro itself also undergoes a conformational change including loosening of the dimeric form. In the complex of lambda‐cro with phi 80‐OR2, which has a 6‐bp sequence common to that of lambda‐OR3, one subunit of the cro dimer seems to bind specifically to the common part. However, there is only a slight conformational change in the cro dimer. In the mixture of the CRP binding site 22‐mer and lambda‐cro, soft contact without any conformational change was observed between them.