Purification and Properties of a Ribonuclease Induced during the Early Larval Development of Artemia salina

Abstract

Dormant gastrulae and developing embryos of the brine shrimp Artemia salina contain very low levels of nuclease activity. During early larval development, there is an induction of a ribonuclease which has been partially purified and characterized. The enzyme catalyzes an endonucleolytic cleavage of RNA and has no detectable activity on native or denatured DNA. Among a series of synthetic polynucleotides, poly(U) is hydrolyzed with the highest efficiency and poly(G) is not cleaved by the enzyme. The activity on poly(U) is 100 times higher than on RNA. The enzyme requires Mg²⁺ or Mn²⁺ and is inactivated by treatment with a chelating agent. The inactive preparations can be reactivated by Ca²⁺ and Mn²⁺ but not by Mg²⁺. The ribonuclease is thermosensitive and has maximal activity at pH 7.5. These properties distinguish the Artemia salina ribonuclease from other eukaryotic ribonucleases already reported. The high activity and specificity of this ribonuclease on poly(U) may suggest a role for this enzyme in the processing of the messenger RNA.