De A, Ramesh V, Mahadevan S, Nagaraja V
Microbiology and Cell Biology Department, Indian Institute of Science, Bangalore.
Biochemistry. 1998 Mar 17;37(11):3831-8. doi: 10.1021/bi972171v.
The contributions from the secondary structure of the transcriptional activator protein C of bacteriophage Mu to its specific DNA binding and the influence of various factors, viz., electrolytes, and minor groove and major groove binders on this protein-DNA interaction have been addressed. Circular dichroism (CD) spectral results suggest that, in the absence of Mg2+, C protein exhibits a beta-pleated sheetlike structure and Mg2+ changes the conformation to a more alpha-helical structure which could provide specific geometrical constraints complementary to those of DNA-helix. Thus, Mg2+ acts as a cofactor for the binding of the C protein to its specific site in DNA by inducing conformational changes in the protein. Competitive binding studies with minor and major groove binding drugs, viz., distamycin A and methyl green, respectively, and the DMS footprinting data indicate that the C protein recognizes the major groove of DNA during complex formation. Further, upon major groove binding, C protein brings about changes in DNA conformation; such conformational changes could have implications in the transcription process.
噬菌体Mu转录激活蛋白C的二级结构对其特异性DNA结合的贡献，以及各种因素，即电解质、小沟和大沟结合剂对这种蛋白质-DNA相互作用的影响，已得到研究。圆二色性（CD）光谱结果表明，在没有Mg2+的情况下，C蛋白呈现β-折叠片状结构，而Mg2+将其构象改变为更具α-螺旋的结构，这可以提供与DNA螺旋互补的特定几何约束。因此，Mg2+通过诱导蛋白质构象变化，作为C蛋白与其在DNA中特定位点结合的辅助因子。分别用小沟和大沟结合药物，即Distamycin A和甲基绿进行的竞争性结合研究以及DMS足迹数据表明，C蛋白在复合物形成过程中识别DNA的大沟。此外，在大沟结合后，C蛋白会引起DNA构象变化；这种构象变化可能对转录过程有影响。
