Zhou H M, Strydom D J
Center for Biochemical and Biophysical Sciences and Medicine, Boston, MA 02115.
Eur J Biochem. 1993 Oct 1;217(1):401-10. doi: 10.1111/j.1432-1033.1993.tb18259.x.
A ribonuclease (RNase) that cleaves specifically on the 3' side of uridine [Shapiro, R., Fett, J. W., Strydom, D. J. & Vallee, B. L. (1986a) Biochemistry 25, 7255-7264] was purified from human plasma and its amino acid sequence was determined. This protein is a 119-residue single-chain polypeptide cross-linked by four disulfide bonds and has an amino-terminal pyroglutaminyl residue. No post-translational modifications were observed during extensive sequence studies on peptide fragments, except for the amino-terminal pyroglutamic acid and a possible deamidation of Asn66. The protein is homologous to the pancreatic ribonucleases and angiogenin, but differs substantially from both of these proteins; the protein sequence has 43% identity with human pancreatic ribonuclease and 39% identity with human angiogenin, as compared to 35% identity between human angiogenin and pancreatic ribonuclease. It is referred to as RNase 4, based on the nomenclature currently used for the genes of pancreatic RNase (RNase 1) and the eosinophil-derived RNases (RNase 2 and RNase 3). Virtually all of the RNase active-site components, including the catalytic residues His12, His119 and Lys41, are preserved. However, some invariant residues of RNase 1 are replaced, e.g. Lys7 by arginine, Asp14 by histidine, and Pro42 by arginine. RNase 4 contains a unique two-residue deletion at the position corresponding to amino acids 77 and 78 of pancreatic RNase, and its carboxyterminal sequence is truncated at position 122. The deletion in angiogenin at position 21 is also found in RNase 4. RNase 4 is very similar to two RNases isolated from bovine and porcine liver, and together they form a new family in the RNase superfamily. The degree of inter-species similarity (90%) is much greater than within the pancreatic RNase and angiogenin families, which suggests that this ribonuclease could possess a physiologically important function other than general RNA catabolism.
一种特异性切割尿苷3'侧的核糖核酸酶（RNase）[夏皮罗，R.，费特，J. W.，斯特里多姆，D. J. & 瓦利，B. L.（1986a）《生物化学》25，7255 - 7264]从人血浆中纯化出来，并测定了其氨基酸序列。该蛋白质是由四个二硫键交联的119个残基的单链多肽，有一个氨基末端焦谷氨酰残基。在对肽片段进行广泛的序列研究过程中，除了氨基末端焦谷氨酸和Asn66可能的脱酰胺作用外，未观察到翻译后修饰。该蛋白质与胰腺核糖核酸酶和血管生成素同源，但与这两种蛋白质有很大不同；与人类胰腺核糖核酸酶相比，其蛋白质序列有43%的同一性，与人类血管生成素相比有39%的同一性，而人类血管生成素和胰腺核糖核酸酶之间的同一性为35%。根据目前用于胰腺RNase（RNase 1）基因和嗜酸性粒细胞衍生的RNase（RNase 2和RNase 3）的命名法，它被称为RNase 4。几乎所有的RNase活性位点成分，包括催化残基His12、His119和Lys41都得以保留。然而，RNase 1的一些不变残基被取代，例如Lys7被精氨酸取代，Asp14被组氨酸取代，Pro42被精氨酸取代。RNase 4在与胰腺RNase氨基酸77和78相对应的位置有一个独特的两个残基缺失，其羧基末端序列在122位被截断。血管生成素在21位的缺失在RNase 4中也有发现。RNase 4与从牛和猪肝中分离出的两种RNase非常相似，它们共同在RNase超家族中形成一个新家族。种间相似程度（90%）远大于胰腺RNase和血管生成素家族内部的相似程度，这表明这种核糖核酸酶可能具有除一般RNA分解代谢之外的生理重要功能。
