CRP-DNA COMPLEXES - INDUCING THE A-LIKE FORM IN THE BINDING-SITES WITH AN EXTENDED CENTRAL SPACER
CRP-DNA COMPLEXES - INDUCING THE A-LIKE FORM IN THE BINDING-SITES WITH AN EXTENDED CENTRAL SPACER
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DOI：
10.1006/jmbi.1994.0019
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发表时间：
1995-01-20
影响因子：
5.6
通讯作者：
ADHYA, S
中科院分区：
文献类型：
--
作者：
IVANOV, VI;MINCHENKOVA, LE;ADHYA, S
用于结合大肠杆菌环AMP受体蛋白（CRP）的共有DNA序列具有两个对称相关的反向识别元件TGTGA：TCACA，由可变间隔区隔开，通常为6 bp长。我们已经表明，CRP-cAMP复合物，当结合到合成的结合位点与一个扩展的8 bp的间隔片段，诱导增加的DNA圆二色性（CD）。λ> 275 nm处的CD变化与DNA的大约一个螺旋圈转变为A样形式一致。CRP结合位点的B-构象与具有6 bp间隔区的Inc和uxaCA启动子中的B-构象相似。伴随DNA结合的另一个效应是在λ < 272 nm处配体cAMP的光谱区域中负CD幅度的急剧增加。当CRP与具有6或8bp间隔区的特异性位点以及与非特异性DNA结合时观察到这种效应。我们推断A样形式是通过压缩和解旋具有8bp中心间隔区的CRP-DNA复合物中的DNA而产生的。这是为了保持一个固定的长度和扭转角度肛门是由蛋白质的相对刚性框架控制。该模型与具有6 bp间隔区的一些结合位点也可能显示具有延伸的8bp间隔区的位点固有的CD增加的观察结果一致。这些6 bp的间隔区的特点是增加的扭曲角，需要他们的解旋结合CRP。我们建议，CRP和结合位点之间的相互适应，通过局部解旋和B-> A-样的转换在DNA中是普遍的重要性，并可能发生在其他蛋白质-DNA复合物，如RNA聚合酶与启动子DNA的复合物。
The consensus DNA sequence for binding of the Escherichia coli cyclic AMP receptor protein (CRP) has two symmetrically related inverted recognition elements TGTGA:TCACA, separated by a variable spacer, normally 6 bp long. We have shown that the CRP-cAMP complex, when bound to synthetic binding sites with an extended 8 bp spacer segment, induces an increase in the DNA circular dichroism (CD). The CD change at lambda > 275 nm agrees with the shift of approximately one helical turn of DNA into A-like form. The B-conformation is preserved for CRP binding sites similar to that in the Inc and uxaCA promoters with 6 bp spacers. Another effect accompanying DNA binding is a dramatic increase of the negative CD magnitude in the spectral region of the ligand cAMP, at lambda < 272 nm. This effect is observed when CRP binds to specific sites with 6 or 8 bp spacers as well as to non-specific DNA.We reason that the A-like form arises by compressing and unwinding the DNA in CRP-DNA complexes having 8 bp central spacers. This serves to maintain a fixed length and twisting angle anal is controlled by the protein's relatively rigid frame. This model is consistent with the observation that some binding sites with 6 bp spacers may also show the CD increase inherent to the sites with the extended 8 bp spacers. These 6 bp spacers are characterized by an increased twisting angle that requires their unwinding to bind to CRP.We propose that a mutual adaptation between CRP and binding sites by local untwisting and a B-->A-like transition in the DNA is of general importance and may occur in other protein-DNA complexes, such as the complex of RNA polymerase with promoter DNA.