Pieler T, Digweed M, Erdmann V A
Institut für Biochemie, Freie Universität Berlin, FRG.
J Biomol Struct Dyn. 1985 Dec;3(3):495-514. doi: 10.1080/07391102.1985.10508437.
The temperature dependent transition from duplex to a single strand in E. coli 5S ribosomal RNA is a multistep process, and it involves intermediate states. We have analyzed these structural dynamics by chemical modification of cytidines and by single strand specific nuclease digestions. This combined approach led to the characterization of premelting and melting transitions within individual structural segments of the native macromolecule, which we feel may find general application to the structure of biological polyribonucleotides: 1) G-C base pairs at the termini of helices are relatively unstable and they readily undergo premelting transition. 2) Internal G-U/A-U rich stretches of helices exhibit dynamic premelting properties. 3) Hairpin loops have a relatively stronger destabilizing effect than internal loops. 4) Bulge loops destabilize the neighbouring base pairs. 5) Melting of helical segments occurs starting from the destabilizing structures listed above, preferentially from the helix termini. E. coli 5S rRNA has been shown to adopt different conformations. The presence of urea leads to induction of enhancement in the sensitivity for nuclease S1 at several nucleotide positions. The possibility of structural rearrangements will be discussed.
大肠杆菌5S核糖体RNA中从双链到单链的温度依赖性转变是一个多步骤过程，且涉及中间状态。我们通过胞嘧啶的化学修饰和单链特异性核酸酶消化来分析这些结构动力学。这种联合方法使得我们能够表征天然大分子各个结构片段内的预熔解和熔解转变，我们认为这可能在生物多聚核糖核苷酸结构中具有普遍应用：1）螺旋末端的G-C碱基对相对不稳定，容易发生预熔解转变。2）螺旋内部富含G-U/A-U的片段表现出动态预熔解特性。3）发夹环比内部环具有相对更强的去稳定化作用。4）凸起环会使相邻碱基对去稳定化。5）螺旋片段的熔解从上述去稳定化结构开始，优先从螺旋末端开始。已表明大肠杆菌5S rRNA会采用不同构象。尿素的存在会导致在几个核苷酸位置对核酸酶S1的敏感性增强。将讨论结构重排的可能性。
