Perreault J P, Altman S
Department of Biology, Yale University, New Haven, CT 06520.
J Mol Biol. 1993 Apr 5;230(3):750-6. doi: 10.1006/jmbi.1993.1197.
The pathway is described for activation by Mg2+ of substrates for M1 RNA, the catalytic subunit of the RNase P from Escherichia coli. The dissociation constants are reported for binding of Mg2+ to the substrate and for the binding of the metal ion-substrate complex to the enzyme. The enzyme binds the substrate with the same affinity whether or not Mg2+ is already bound to the substate. However, only substrates with bound Mg2+ can make a productive ternary complex when combined with the enzyme. The presence of certain 2'-hydroxyl groups in the substrate is required to stabilize the binding of Mg2+ and, thereby, to increase the lifetime of the ternary complex. An energy profile for the reaction of M1 RNA with a small model substrate is presented and the role of Mg2+ bound to the substrate is discussed.
本文描述了Mg2+激活大肠杆菌核糖核酸酶P的催化亚基M1 RNA底物的途径。报告了Mg2+与底物结合以及金属离子-底物复合物与酶结合的解离常数。无论Mg2+是否已经与底物结合，酶都以相同的亲和力结合底物。然而，只有结合了Mg2+的底物与酶结合时才能形成有活性的三元复合物。底物中某些2'-羟基的存在是稳定Mg2+结合所必需的，从而增加三元复合物的寿命。给出了M1 RNA与小模型底物反应的能量分布图，并讨论了结合在底物上的Mg2+的作用。
