Yakovlev G, Moiseyev G P, Sorrentino S, De Prisco R, Libonati M
Engelhardt Institute of Molecular Biology, Russian Academy of Sciences, Moscow, Russia.
J Biomol Struct Dyn. 1997 Oct;15(2):243-50. doi: 10.1080/07391102.1997.10508189.
To establish the mechanism of dsRNA degradation by mammalian single-stranded-preferring ribonucleases, and, in particular, the influence of their positively charged non-catalytic amino acid residues, we have studied the kinetic parameters of the depolimerization of single- and double-stranded polyribonucleotides such as poly(U), poly(U).poly(A), poly(C) and poly(C).poly(I) by the action of human seminal RNase, bovine seminal RNase and ox pancreas RNase A. While the activities of these RNases on poly(I).poly(C) were definitely lower than those on poly(C), the activities of human seminal and bovine seminal RNases on poly(U).poly(A) and poly(U) were of the same order of magnitude under physiological salt conditions. The ratio of the RNase A degrading activities towards poly(U) and poly(U).poly(A) at I = 0.16 M is ten times higher than the corresponding ratios determined with bovine seminal and human seminal ribonucleases. The high activities of these two RNases towards poly(U).poly(A) are discussed on the basis of their efficient estabilishing action on this double-helical nucleic acid due to their high affinity for poly(A). The destabilizing action of human seminal RNase and bovine seminal RNase on the poly (U).poly(A) duplex is higher than that measurable with bovine RNase A because of the higher number of positive charges present on those enzyme molecules. This may therefore explain why human seminal and bovine seminal ribonucleases are more efficient than RNase A in the depolymerization of poly(U).poly(A) at physiological ionic strength.
为了确定哺乳动物单链偏好性核糖核酸酶降解双链RNA的机制，尤其是其带正电荷的非催化氨基酸残基的影响，我们研究了人精浆核糖核酸酶、牛精浆核糖核酸酶和牛胰核糖核酸酶A作用下单链和双链多聚核糖核苷酸（如聚尿苷酸、聚尿苷酸·聚腺苷酸、聚胞苷酸和聚胞苷酸·聚肌苷酸）解聚的动力学参数。虽然这些核糖核酸酶对聚肌苷酸·聚胞苷酸的活性明显低于对聚胞苷酸的活性，但在生理盐条件下，人精浆核糖核酸酶和牛精浆核糖核酸酶对聚尿苷酸·聚腺苷酸和聚尿苷酸的活性处于同一数量级。在离子强度I = 时，核糖核酸酶A对聚尿苷酸和聚尿苷酸·聚腺苷酸的降解活性之比比用牛精浆核糖核酸酶和人精浆核糖核酸酶测定的相应比值高10倍。基于这两种核糖核酸酶对聚腺苷酸的高亲和力，对聚尿苷酸·聚腺苷酸这种双螺旋核酸具有高效的稳定作用，讨论了它们对聚尿苷酸·聚腺苷酸的高活性。由于这些酶分子上存在更多的正电荷，人精浆核糖核酸酶和牛精浆核糖核酸酶对聚尿苷酸·聚腺苷酸双链的去稳定作用高于用牛核糖核酸酶A可测量的作用。因此，这可能解释了为什么在生理离子强度下，人精浆核糖核酸酶和牛精浆核糖核酸酶在聚尿苷酸·聚腺苷酸解聚方面比核糖核酸酶A更有效。
