Takahashi M, Kubista M, Nordén B
J Biol Chem. 1987 Jun 15;262(17):8109-11.
In the presence of RecA single-stranded DNA (ssDNA) is found to exhibit flow linear dichroism (LD). In the absence of the cofactor ATP gamma S, the LD is positive with a maximum at about 280 nm, whereas in the presence of the cofactor ATP gamma S there is still a positive long-wavelength band, but a negative LD contribution centered at 260 nm indicates an orientation of the DNA bases preferentially perpendicular to the fiber axis. For the complex between ssDNA and RecA without ATP gamma S, essentially all LD derives from the protein (tryptophane) subunits indicating a structure in which the tryptophanes are preferentially parallel to the fiber axis of the complex while the DNA bases remain essentially unoriented. The magnitude of the LD increases with the RecA/DNA ratio to a point corresponding to approximately three nucleotides per RecA and decreases thereafter with excess of DNA. This indicates that there are two modes of binding with different stoichiometries.
在RecA存在的情况下，发现单链DNA（ssDNA）表现出流动线性二色性（LD）。在没有辅因子ATPγS的情况下，LD为正，在约280nm处有最大值，而在辅因子ATPγS存在的情况下，仍然有一个正的长波带，但以260nm为中心的负LD贡献表明DNA碱基优先垂直于纤维轴的取向。对于没有ATPγS的ssDNA与RecA之间的复合物，基本上所有的LD都来自蛋白质（色氨酸）亚基，这表明色氨酸优先平行于复合物的纤维轴，而DNA碱基基本上没有取向的结构。LD的大小随着RecA/DNA比例增加到对应于每个RecA约三个核苷酸的点，此后随着DNA过量而降低。这表明存在两种具有不同化学计量比的结合模式。
