Pace B, Stahl D A, Pace N R
J Biol Chem. 1984 Sep 25;259(18):11454-8.
The Bacillus subtilis RNase M5 complex, responsible for the terminal maturation of 5 S rRNA, includes two proteins. One of these proteins is ribosomal protein BL16 (equivalent to Escherichia coli EL18); the other, the alpha component, is required for catalysis. The RNase M5 alpha component has been purified in bulk extensively, and the active polypeptide (Mr approximately 24,000) identified following polyacrylamide gel electrophoresis. Reaction conditions (20-30% dimethyl sulfoxide) are reported which render RNase M5 activity independent of ribosomal protein BL16. This proves that alpha indeed is the catalytic element, the actual RNase M5, which normally attacks a ribonucleoprotein substrate consisting of protein BL16 in complex with the 5 S rRNA precursor. Kinetic analyses of the BL16-dependent and independent reactions suggest that any alpha-BL16 association contributes little to the energetics of the alpha-ribonucleoprotein substrate interaction. It is postulated that the BL16 protein serves as a scaffold, to lock the precursor mRNA into a conformation recognizable by the nuclease.
负责5S rRNA末端成熟的枯草芽孢杆菌核糖核酸酶M5复合物包含两种蛋白质。其中一种蛋白质是核糖体蛋白BL16（等同于大肠杆菌EL18）；另一种α组分是催化所必需的。核糖核酸酶M5的α组分已被大量广泛纯化，并在聚丙烯酰胺凝胶电泳后鉴定出活性多肽（分子量约为24,000）。报告了使核糖核酸酶M5活性独立于核糖体蛋白BL16的反应条件（20 - 30%二甲基亚砜）。这证明α确实是催化元件，即实际的核糖核酸酶M5，它通常攻击由与5S rRNA前体复合的蛋白质BL16组成的核糖核蛋白底物。对依赖BL16和不依赖BL16的反应的动力学分析表明，任何α - BL16缔合对α - 核糖核蛋白底物相互作用的能量学贡献很小。据推测，BL16蛋白充当支架，将前体mRNA锁定为核酸酶可识别的构象。
