TMS5 encodes an RNase Z^S1 protein that can process ubiquitin-60S ribosomal protein L40 family (Ub_L40) mRNAs to regulate thermo-sensitive genic male sterility in rice. Despite the importance of this protein, the structural characteristics and substrate recognition properties of RNase Z^S1 remain unclear. Here, we found that the variations in several conservative amino acids alter the activation of RNase Z^S1, and its recognition of RNA substrates depends on the structure of RNA. RNase Z^S1 acts as a homodimer. The conserved amino acids in or adjacent to enzyme center play a critical role in the enzyme activity of RNase Z^S1 and the conserved amino acids that far from active center have little impact on its enzyme activity. The cleavage efficiency of RNase Z^S1 for pre-tRNA-MetCAU35 and Ub_L401 mRNA with cloverleaf-like structure was higher than that of pre-tRNA-AspAUC9 and Ub_L404 mRNA with imperfect cloverleaf-like structure. This difference implies that the enzyme activity of RNase Z^S1 depends on the cloverleaf-like structure of the RNA. Furthermore, the RNase Z^S1 activity was not inhibited by the 5′ leader sequence and 3’ CCA motif of pre-tRNA. These findings provide new insights for studying the cleavage characteristics and substrate recognition properties of RNase Z^S.

TMS5编码一种RNase Z ^S1蛋白，该蛋白可以处理遍在蛋白60S核糖体蛋白L40家族（Ub _L40）mRNA，以调节水稻的热敏性雄性不育。尽管该蛋白很重要，但RNase Z ^S1的结构特征和底物识别特性仍不清楚。在这里，我们发现几种保守氨基酸的变异改变了RNase Z ^S1的激活，其对RNA底物的识别取决于RNA的结构。RNase Z ^S1充当同源二聚体。酶中心内或附近的保守氨基酸在RNase Z ^S1的酶活性中起关键作用远离活性中心的保守氨基酸对其酶的活性影响很小。RNase Z ^S1对具有三叶形结构的前tRNA-MetCAU35和Ub _L40 1 mRNA的切割效率高于具有不完整三叶形结构的pre-tRNA-AspAUC9和Ub _L40 4 mRNA。这种差异意味着RNase Z ^S1的酶活性取决于RNA的苜蓿叶状结构。此外，RNase Z ^S1活性不受pre-tRNA的5'前导序列和3'CCA基序抑制。这些发现为研究RNase Z的裂解特性和底物识别特性提供了新的见解。^小号。