Eichler D C, Eales S J
J Biol Chem. 1982 Dec 10;257(23):14384-9.
An endoribonuclease which cleaves only single-stranded RNA has been purified from nucleoli of Ehrlich ascites tumor cells. The molecular weight of the ribonuclease is 50,000 to 52,000 as estimated from sedimentation in glycerol density gradients and by gel filtration on Sephadex G-100. The endoribonuclease requires Mg2+ or Mn2+ (0.2 mM) for optimum activity. Monovalent cations including K+, Na+, and NH+4 are inhibitory. The ribonuclease gave an apparent Km for single-stranded RNA of 30 microM. Using ribohomopolymers, we found that the enzyme could digest single-stranded, poly(C), poly(U), and poly(A) equally well, but would not degrade duplex poly(C) . poly(I) or poly(A) . poly(U). The lack of base specificity was further demonstrated using RNA sequence analysis of partial digest products of yeast 5.8 S RNA. The ribonuclease activity is sensitive to EDTA and N-ethylmaleimide, but is not inhibited by human placental RNase inhibitor. The enzyme makes endonucleolytic cleavages which generate 5'-phosphate-terminated oligonucleotides.
一种仅切割单链RNA的核糖核酸内切酶已从艾氏腹水瘤细胞的核仁中纯化出来。根据在甘油密度梯度中的沉降和在Sephadex G - 100上的凝胶过滤估计，该核糖核酸酶的分子量为50,000至52,000。该核糖核酸内切酶需要Mg2+或Mn2+（0.2 mM）以达到最佳活性。包括K+、Na+和NH4+在内的单价阳离子具有抑制作用。该核糖核酸酶对单链RNA的表观Km为30 microM。使用核糖同聚物，我们发现该酶能同样良好地消化单链的聚（C）、聚（U）和聚（A），但不会降解双链聚（C）·聚（I）或聚（A）·聚（U）。使用酵母5.8 S RNA部分消化产物的RNA序列分析进一步证明了其缺乏碱基特异性。该核糖核酸酶活性对EDTA和N - 乙基马来酰亚胺敏感，但不受人胎盘核糖核酸酶抑制剂抑制。该酶进行内切核酸酶切割，产生5'-磷酸末端的寡核苷酸。
