Purification and Properties of Double-stranded RNA-degrading Nuclease,dsRNase, from the Digestive Juice of the Silkworm, Bombyx mori

抄録

A nuclease which degrades double-stranded RNA was purified from the digestive juice of fifth-instar larvae of the silkworm, Bombyx mori, using gel filtration and affinity column chromatography. The enzyme was found to have a molecular weight of 41,000 as estimated by a gel filtration method and detected as a single band with the same molecular weight on polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate. It degraded double-stranded RNA of cytoplasmic polyhedrosis virus genome, synthetic Poly(I)/Poly(C), Poly(I) and Poly(C). It also digested copolymer Poly(AU), Poly(A) and Poly(U), but showed weak degradation of Poly(A)/Poly(U), Poly(C)/Poly(G), Poly(G) and natural DNA isolated from calf thymus. The pH range wherein the reaction occurred was greater than 7. The purified enzyme did not require Mg²⁺ to degrade CPV-dsRNA, whereas divalent cations including Mg²⁺ and Ca²⁺ were needed to degrade synthetic Poly(I)/Poly(C). The enzyme activity was suppressed by Co²⁺, Zn²⁺ and Mn²⁺.