Cell：首次发现不含RNA的酶RNA

　　

生物通报道，来自奥地利维也纳大学医学院解剖与细胞生物学中心，维也纳大学医学院癌症研究所，维也纳高等院校分子医学研究中心的科学家近期发现了一种不含RNA的核酶（又称酶RNA）。相关的研究文章发表在10月31日的Cell上。

 

众所周知核酶（ribozyme）是具有催化功能的RNA分子。核酶又称核酸类酶、酶RNA、类酶RNA。

 

在tRNA成熟前，前体tRNA的5’端有一段额外的核苷酸会被一种核酸内切酶名为Rnase P的酶切除下来，经过这一过程前体tRNA方成为成熟的具有生物功能的成熟tRNA。

 

迄今为止，所有已发现的Rnase（核酶）都是由一个RNA加一个或多个蛋白所构成，并且在tRNA成熟的过程中Rnase负责去尾促进tRNA成熟。

 

Walter Rossmanith带领的研究小组通过蛋白质纯化技术将人类线粒体Rnase P酶的蛋白成分纯化出来，并通过蛋白重组技术将三个蛋白组合起来，获得Rnase P的活性。因此，研究小组认为，人类线粒体Rnase P酶是一种蛋白质酶，它并不需要反式作用RNA（trans-acting RNA）就能发挥催化活性。

 

研究者对线粒体酶进行分析发现，组成线粒体酶的还有多种酶，比如tRNA甲基转移酶，一个短链脱氢酶（还原酶家族成员），以及一个至今不清楚活性的蛋白质。

 

原文摘要：RNase P without RNA: Identification and Functional Reconstitution of the Human Mitochondrial tRNA Processing Enzyme

 

【Summary】

tRNAs are synthesized as immature precursors, and on their way to functional maturity, extra nucleotides at their 5′ ends are removed by an endonuclease called RNase P. All RNase P enzymes characterized so far are composed of an RNA plus one or more proteins, and tRNA 5′ end maturation is considered a universal ribozyme-catalyzed process. Using a combinatorial purification/proteomics approach, we identified the components of human mitochondrial RNase P and reconstituted the enzymatic activity from three recombinant proteins. We thereby demonstrate that human mitochondrial RNase P is a protein enzyme that does not require a trans-acting RNA component for catalysis. Moreover, the mitochondrial enzyme turns out to be an unexpected type of patchwork enzyme, composed of a tRNA methyltransferase, a short-chain dehydrogenase/reductase-family member, and a protein of hitherto unknown functional and evolutionary origin, possibly representing the enzyme's metallonuclease moiety. Apparently, animal mitochondria lost the seemingly ubiquitous RNA world remnant after reinventing RNase P from preexisting components.

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