Takeda Y, Nara H, Iwahashi K, Mitsui Y, Iitaka Y
J Biochem. 1983 Jul;94(1):275-82. doi: 10.1093/oxfordjournals.jbchem.a134340.
The interactions of putrescine, the major diamine in E. coli, with E. coli DNA as a model of phage DNA were studied by melting temperature analysis, equilibrium dialysis and X-ray diffraction with the aid of molecular model building. The chemical analysis of the DNA-putrescine complex shows that the molar binding ratio of putrescine to DNA (phosphate) is nearly 1 to 2. The equilibrium (or reversible) binding of putrescine to DNA was suggested by the fact that the melting temperature increased according to the concentration of added putrescine, and its elevation was not saturated even at the molar ratio of 6 to 1. The equilibrium dialysis experiments indicate that the association constant for the complex is a little smaller than, but in the same order (10(3) liter/mol) as, that of DNA-spermine complex. The binding of putrescine stabilizes the B-form of DNA fiber, which is well preserved even at 66% relative humidity. The distance between the neighboring DNA helices in the wet fiber increased with the increasing degree of hydration, as in the case of native DNA. Unlike spermine, putrescine does not form precipitate upon mixing with DNA in the concentration range for UV measurement, suggesting that the cross-bridge formed by putrescine is intra-double helical. The equilibrium binding of putrescine to DNA, seems to be important for the life cycle of lambda-phage.
以大肠杆菌DNA作为噬菌体DNA的模型，通过解链温度分析、平衡透析以及借助分子模型构建的X射线衍射，研究了大肠杆菌中主要二胺腐胺与大肠杆菌DNA的相互作用。DNA-腐胺复合物的化学分析表明，腐胺与DNA（磷酸）的摩尔结合比接近1比2。腐胺与DNA的平衡（或可逆）结合是由以下事实表明的：解链温度随添加腐胺的浓度而升高，即使在摩尔比为6比1时其升高也未达到饱和。平衡透析实验表明，该复合物的缔合常数略小于DNA-精胺复合物，但处于相同数量级（10³升/摩尔）。腐胺的结合使DNA纤维的B型结构稳定，即使在相对湿度为66%时也能很好地保持。与天然DNA的情况一样，湿纤维中相邻DNA螺旋之间的距离随水合程度的增加而增加。与精胺不同，在紫外测量的浓度范围内，腐胺与DNA混合时不会形成沉淀，这表明腐胺形成的交联桥是在双螺旋内部。腐胺与DNA的平衡结合似乎对λ噬菌体的生命周期很重要。
