Kohwi-Shigematsu T, Enomoto T, Yamada M A, Nakanishi M, Tsuboi M
Proc Natl Acad Sci U S A. 1978 Oct;75(10):4689-93. doi: 10.1073/pnas.75.10.4689.
The reaction of chloroacetaldehyde with adenine bases in DNA to give a fluorescent product was used to study the availability to intermolecular reaction of positions 1 and 6 of adenine in DNA complexes with calf thymus DNA helix-destabilizing protein. No inhibition of this reaction was observed when heat-denatured DNA was complexed with the protein at a protein/DNA weight ratio of 10:1, compared to free DNA. On the contrary, the same reaction was inhibited markedly for denatured DNA in the presence of calf thymus histone HI at protein/DNA weight ratio of 2:1. Furthermore, the exchange rate for hydrogens of amino and imide groups of DNA bases in DNA strands with deuterium in the solvent was totally unaffected upon complexing of DNA with the DNA helix-destabilizing protein as examined by stopped-flow ultraviolet spectroscopy. These results indicate that the DNA helix-destabilizing protein forms a complex with single-stranded DNA, leaving DNA bases uncovered by the protein. The fluorescence intensity of DNA pretreated with chloroacetaldehyde was amplified by nearly 3-fold upon addition of the DNA helix-destabilizing protein. The possibility of "unstacking" of DNA bases induced by the protein is discussed.
利用氯乙醛与DNA中的腺嘌呤碱基反应生成荧光产物,来研究在与小牛胸腺DNA螺旋去稳定蛋白形成的DNA复合物中,腺嘌呤第1位和第6位发生分子间反应的可能性。与游离DNA相比,当热变性DNA与蛋白以蛋白/DNA重量比为10:1复合时,未观察到该反应受到抑制。相反,在小牛胸腺组蛋白H1存在下,当蛋白/DNA重量比为2:1时,变性DNA的相同反应受到明显抑制。此外,通过停流紫外光谱法检测发现,DNA链中DNA碱基的氨基和亚氨基上的氢与溶剂中的氘的交换速率在DNA与DNA螺旋去稳定蛋白复合后完全不受影响。这些结果表明,DNA螺旋去稳定蛋白与单链DNA形成复合物,使DNA碱基未被蛋白覆盖。加入DNA螺旋去稳定蛋白后,用氯乙醛预处理的DNA的荧光强度增加了近3倍。文中讨论了该蛋白诱导DNA碱基“解堆积”的可能性。