一小组细菌编码两种类型的RNaseP,经典的核糖核蛋白(RNP)RNaseP以及仅蛋白质RNasePHARP(AquifexRNaseP的同源物)。我们表征了属于三个不同门的五种细菌的双重RNaseP活性。所有五种细菌都编码RNPRNaseP的功能性RNA(基因rnpB)和蛋白质(基因rnpA)亚基,但是在大肠杆菌RNaseP耗竭菌株中,仅发现嗜热脱硫杆菌(热脱硫杆菌门)的HARP在体外和体内具有强大的tRNA5'端成熟活性。这些发现表明,两种类型的RNaseP都能够促进T.indicus的必需tRNA5'端成熟活性,因此类似于在该细菌家族中rnpA和rnpB基因丢失之前,Aquificaceae祖先的预测进化过渡状态。值得注意的是,T.indicusRNasePRNA转录了P12扩增片段,该片段在体内转录后切除,使得RNA的主要部分被片段化,从而在天然的T.indicus宿主以及在大肠杆菌互补菌株中被截短~70nt。用ThermotogamaritimaRNasePRNA的短P12螺旋代替T的天然P12元件消除了片段化,但同时损害了大肠杆菌细胞的互补效率,这表明T.indicusRNasePRNA的细胞内片段化和截短可能有利于RNA折叠和/或酶活性。
A small group of bacteria encode two types of RNase P, the classical ribonucleoprotein (RNP) RNase P as well as the protein-only RNase P HARP (homolog of Aquifex RNase P). We characterized the dual RNase P activities of five bacteria that belong to three different phyla. All five bacterial species encode functional RNA (gene rnpB) and protein (gene rnpA) subunits of RNP RNase P, but only the HARP of the thermophile Thermodesulfatator indicus (phylum Thermodesulfobacteria) was found to have robust tRNA 5\'-end maturation activity in vitro and in vivo in an Escherichia coli RNase P depletion strain. These findings suggest that both types of RNase P are able to contribute to the essential tRNA 5\'-end maturation activity in T. indicus, thus resembling the predicted evolutionary transition state in the progenitor of the Aquificaceae before the loss of rnpA and rnpB genes in this family of bacteria. Remarkably, T. indicus RNase P RNA is transcribed with a P12 expansion segment that is posttranscriptionally excised in vivo, such that the major fraction of the RNA is fragmented and thereby truncated by ∼70 nt in the native T. indicus host as well as in the E. coli complementation strain. Replacing the native P12 element of T. indicus RNase P RNA with the short P12 helix of Thermotoga maritima RNase P RNA abolished fragmentation, but simultaneously impaired complementation efficiency in E. coli cells, suggesting that intracellular fragmentation and truncation of T. indicus RNase P RNA may be beneficial to RNA folding and/or enzymatic activity.