Department of Biological Chemistry, University of Michigan, Ann Arbor, MI, USA.
RNA Biol. 2013 Jun;10(6):909-14. doi: 10.4161/rna.24513. Epub 2013 Apr 1.
Ribonuclease P (RNase P) catalyzes the maturation of the 5' end of precursor-tRNAs (pre-tRNA) and is conserved in all domains of life. However, the composition of RNase P varies from bacteria to archaea and eukarya, making RNase P one of the most diverse enzymes characterized. Most known RNase P enzymes contain a large catalytic RNA subunit that associates with one to 10 proteins. Recently, a protein-only form of RNase P was discovered in mitochondria and chloroplasts of many higher eukaryotes. This proteinaceous RNase P (PRORP) represents a new class of metallonucleases. Here we discuss our recent crystal structure of PRORP1 from Arabidopsis thaliana and speculate on the reasons for the replacement of catalytic RNA by a protein catalyst. We conclude, based on an analysis of the catalytic efficiencies of ribonucleoprotein (RNP) and PRORP enzymes, that the need for greater catalytic efficiency is most likely not the driving force behind the replacement of the RNA with a protein catalyst. The emergence of a protein-based RNase P more likely reflects the increasing complexity of the biological system, including difficulties in importation into organelles and vulnerability of organellar RNAs to cleavage.
核糖核酸酶 P（RNase P）催化前体 tRNA（pre-tRNA）5'端的成熟，存在于所有生命领域中。然而，RNase P 的组成在细菌、古菌和真核生物中有所不同，使其成为最具多样性的酶之一。大多数已知的 RNase P 酶包含一个与一个到十个蛋白质结合的大型催化 RNA 亚基。最近，在许多高等真核生物的线粒体和叶绿体中发现了一种仅由蛋白质组成的 RNase P。这种蛋白 RNase P（PRORP）代表了一类新的金属核酸酶。在这里，我们讨论了我们最近从拟南芥中获得的 PRORP1 的晶体结构，并推测了用蛋白质催化剂替代催化 RNA 的原因。我们根据核糖核蛋白（RNP）和 PRORP 酶的催化效率分析得出结论，对更高催化效率的需求不太可能是用蛋白质催化剂替代 RNA 的驱动力。蛋白质基 RNase P 的出现更可能反映了生物系统复杂性的增加，包括导入细胞器的困难和细胞器 RNA 易被切割的脆弱性。
