植物中tRNaseZ同源蛋白的鉴定和分析

Identification and sequence analysis of plant tRNase Z homologous proteins

tRNase Z是金属-β-内酰胺酶(MBL)超家族中的一员,它与pre-tRNA 3'末端的成熟加工相关。人们普遍对微生物和动物的tRNase Z研究较多,但对植物的tRNase Z认识很少。为了更好地了解植物tRNase Z,我们对10种已测序植物进行tRNase Z同源检索并分析。研究表明植物中存在3种tRNase Z,细菌型tRNase ZS只存在于低等的陆生植物和绿藻类植物中,真核型tRNase ZL和海栖热袍菌型tRNase ZS广泛存在于各类植物中。海栖热袍菌tRNase ZS具有独特的保守模体:KL模体、EgxSxxG模体、xHxT模体和HxH模体。对开花植物的tRNase ZS定位预测显示,海栖热袍菌型tRNase ZS定位于植物细胞的叶绿体中。进一步分析发现,低等植物中存在一些没有tRNase Z活性的tRNase Z-like蛋白。试验结果显示植物的tRNase Z比真菌和动物的更加丰富。海栖热袍菌型tRNase ZS和tRNase Z-like蛋白的发现,丰富了tRNase Z家族,加深了人们对tRNase Z的认识。

As a part of the metallo-β-lactamase（ MBL） superfamily,tRNA 3＇-end maturation is a process through which the 3＇-trailer sequence of precursor tRNAs（ pre-tRNAs） is removed. Compared with microbe and animals,there are fewer reports on tRNase Z in plants. Then we analyzed tRNase Z homologous proteins in 10 plants whose whole genome sequencing have been completed. It appeared that plants contained multiple distinct tRNase Zs predicted to reside in different subcellular compartments. Furthermore,while the bacterial-type tRNase Z^Ss are present only in basal land plants and green algae,the eukaryotic-type tRNase Z^Land TM-type tRNase Z^Ss are widespread in plants. The protein sequences of the TM-type tRNase Z^Ss identified in plants are similar to those of the bacterial-type tRNase Z^Ss,but have distinct features,including the TM-type flexible arm,the variant catalytic HEAT and HST motifs,and a lack of the PxKxRN motif. By prediction of flowering plant tRNase Z^Ss,we found that TM-type tRNase Z^Ss had a chloroplast signal sequence. Furthermore,while we analyzed the tRNase Z sequences,we mined some tRNase Z-like proteins in basal land palnts and green algae. Our results revealed that the tRNase Z was more various in plants than fungi and animal. We thus expanded the TM-type tRNase Z^Sfamily in plant and firstly predicted tRNase Z^L-like protein.