In Vivo Function of tRNase Z in Esherichia coli and Yeast Saccharomyces cerevisiae

在大多数生物体中，tRNase Z被认为对tRNA分子的3 '加工至关重要。然而，大肠杆菌tRNase ZS基因在正常生长条件下似乎是可有可无的。在这里，我们深入研究了大肠杆菌tRNase ZS体外良好底物的各种（预）trna，发现该酶可以蚕食成熟trna的3 '端CCA残基。此外，我们发现大肠杆菌tRNase ZS在细胞中充分表达时，通过去除氨基酰基trna中的氨基酸来关闭生长。目前的数据表明，tRNase ZS可能通过抑制某些应激条件下的翻译来帮助调节细胞生长速率。我们还在体外检测了重组酵母tRNase ZL对多种酵母前trna的3 '加工活性。重组酵母tRNase ZL在鉴定核苷酸后能够高效地切割酵母前trna。综上所述，我们推测大肠杆菌和酵母之间tRNase Z结构域结构的差异可能导致了底物识别和切割位点的特异性。

In most organisms, tRNase Z is thought to be essential for 3′ processing of tRNA molecules. The Escherichia coli tRNase ZS gene, however, appears to be dispensable under normal growth conditions. Here we intensively examined various (pre-)tRNAs for good substrates of E. coli tRNase ZS in vitro, and found that the enzyme can nibble off the 3′ terminal CCA residues from mature tRNAs. Furthermore, we discovered that E. coli tRNase ZS, when sufficiently expressed in the cell, shuts down growth by removing amino acids from aminoacyl-tRNAs. The current data suggest that tRNase ZS may help modulate a cell growth rate by repressing translation under some stressful conditions. We also examined 3′ processing activity of recombinant yeast tRNase ZL against various yeast pre-tRNAs in vitro. The recombinant yeast tRNase ZL was able to cleavage yeast pre-tRNAs efficiently after the discriminator nucleotide. Taken together, we speculate the difference of tRNase Z domain structure between E. coli and yeast might lead to the specificity of substrate recognition and cleavage site.