G Ribitsch, R De Clercq, W Folkhard, P Zipper, J Schurz, J Clauwaert
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引用次数: 9
Abstract
The influence of Mg2+ ions on the secondary and tertiary structure of the RNA from bacteriophage MS2 was investigated by small-angle X-ray scattering and light scattering and by sedimentation experiments. The analysis of the outer part of the X-ray scattering curve obtained at low temperature in the absence of Mg2+ yielded a cross-section radius of gyration of 0.88 nm and a mass per unit length of 1720 g mol-1 nm-1. Very similar values for these parameters, which refer to the secondary structure of the RNA molecule, were also derived from the X-ray scattering curves obtained in the presence of different amounts of Mg2+ (0.07 to 1 ions per nucleotide). On the contrary, the inner part of the X-ray scattering curves turned out to be highly dependent on the Mg2+ concentration: the cross-section radius of gyration and the mass per unit length, which were determined from the scattering curves at small angles as parameters related to the tertiary structure of the RNA, amounted to 3.11 nm and 4000 g mol-1 nm-1, respectively, in the absence of Mg2+ and increased significantly upon raising the concentration of Mg2+. The increase of these structural parameters was found to be accompanied by a decrease of the overall radius of gyration (as revealed indirectly by X-ray scattering and directly by light scattering measurements) and by an increase of the sedimentation coefficient. The results from the investigations of the RNA at low temperature clearly establish the existence of double-stranded structures down to very low Mg2+ concentrations as well as the occurrence of Mg2+ induced changes of the tertiary structure.(ABSTRACT TRUNCATED AT 250 WORDS)
采用小角x射线散射、光散射和沉降实验研究了Mg2+离子对噬菌体MS2中RNA二级和三级结构的影响。在没有Mg2+的情况下,对低温下获得的x射线散射曲线的外部进行分析,得到的截面旋转半径为0.88 nm,单位长度的质量为1720 g mol-1 nm-1。这些参数(指RNA分子的二级结构)的非常相似的值也可以从不同量的Mg2+(每核苷酸0.07到1个离子)存在下获得的x射线散射曲线中得到。相反,x射线散射曲线的内部部分高度依赖于Mg2+的浓度:在没有Mg2+的情况下,由小角度散射曲线确定的与RNA的第三级结构有关的截面旋转半径和单位长度质量分别为3.11 nm和4000 g mol-1 nm-1,随着Mg2+浓度的增加,它们显著增加。发现这些结构参数的增加伴随着总旋转半径的减小(由x射线散射间接和光散射测量直接揭示)和沉降系数的增加。低温下对RNA的研究结果清楚地证实了低Mg2+浓度下双链结构的存在以及Mg2+诱导的三级结构变化的发生。(摘要删节250字)