Walter F, Murchie A I, Duckett D R, Lilley D M
CRC Nucleic Acid Structure Research Group, Department of Biochemistry, The University of Dundee, United Kingdom.
RNA. 1998 Jun;4(6):719-28. doi: 10.1017/s135583829898030x.
Four-way helical junctions are found widely in natural RNA species. In this study, we have studied the conformation of two junctions by fluorescence resonance energy transfer. We show that the junctions are folded by pairwise coaxial helical stacking, forming one predominant stacking conformer in both examples studied. At low magnesium ion concentrations, the helical axes of both junctions are approximately perpendicular. One junction undergoes a rotation into a distorted antiparallel structure induced by the binding of a single magnesium ion. By contrast, the axes of the four-way junction of the U1 snRNA remain approximately perpendicular under all conditions examined, and we have determined the stacking conformer adopted.
四向螺旋连接广泛存在于天然RNA分子中。在本研究中，我们通过荧光共振能量转移研究了两个连接的构象。我们表明，连接通过成对的同轴螺旋堆积折叠，在所研究的两个例子中都形成了一种主要的堆积构象。在低镁离子浓度下，两个连接的螺旋轴近似垂直。其中一个连接在单个镁离子结合的诱导下发生旋转，形成扭曲的反平行结构。相比之下，U1 snRNA的四向连接的轴在所有检测条件下都近似垂直，并且我们已经确定了其采用的堆积构象。
