Kariu T, Sano K, Shimokawa H, Itoh R, Yamasaki N, Kimura M
Laboratory of Biochemistry, Faculty of Agriculture, Kyushu University, Fukuoka, Japan.
Biosci Biotechnol Biochem. 1998 Jun;62(6):1144-51. doi: 10.1271/bbb.62.1144.
A wound-inducible ribonuclease (RNase NW) was purified from leaves of Nicotiana glutinosa. The purified RNase NW has an optimum pH around 5 and 7, and its base specificity is suggested based on the relative rates of hydrolysis of homopolyribonucleotides to be a preference for guanine base. The complete amino acid sequence of RNase NW was deduced by a combination of protein and cDNA sequencings. The cDNA sequence includes the entire coding sequence for a polypeptide with 229 amino acids including a putative secretion signal peptide at the N-terminus composed of 25 amino acids. The amino acids identified by the protein chemical methods are unambiguously localized within the deduced amino acid sequence from the cDNA sequence. Comparison of the sequence of RNase NW with those of other known plant RNases showed that it was identical except for eight residues to that of N. alata RNase NE, which is present in the style and pollen under normal conditions and is induced in roots in response to phosphate starvation [Dodds et al., Plant. Mol. Biol., 31, 227-238 (1996)]. RNase NW shows considerable sequence similarity to other known RNases, sharing 57% to 84% identical residues. Northern blot analysis using an RNase NW cDNA fragment as a probe showed that the RNase NW transcript was not detected in leaves without wounding, but it was induced within 4 h after wounding and then gradually decreased during 20 h.
从粘毛烟草叶片中纯化出一种伤口诱导型核糖核酸酶（RNase NW）。纯化后的RNase NW的最适pH值约为5和7，根据同聚核糖核苷酸的相对水解速率推测其碱基特异性为对鸟嘌呤碱基有偏好。通过蛋白质测序和cDNA测序相结合的方法推导得到了RNase NW的完整氨基酸序列。该cDNA序列包含一个由229个氨基酸组成的多肽的完整编码序列，在N端有一个由25个氨基酸组成的假定分泌信号肽。通过蛋白质化学方法鉴定的氨基酸明确地定位在从cDNA序列推导得到的氨基酸序列中。将RNase NW的序列与其他已知植物核糖核酸酶的序列进行比较，结果表明，除了8个残基外，它与烟草RNase NE的序列相同，RNase NE在正常条件下存在于花柱和花粉中，在根部受到磷饥饿诱导时产生[多兹等人，《植物分子生物学》，31，227 - 238（1996）]。RNase NW与其他已知核糖核酸酶显示出相当大的序列相似性，相同残基的比例为57%至84%。使用RNase NW cDNA片段作为探针进行的Northern印迹分析表明，在未受伤的叶片中未检测到RNase NW转录本，但在受伤后4小时内被诱导，然后在20小时内逐渐减少。
