BREAKDOWN OF DOUBLE-STRANDED RNA BY BULL SEMEN RIBONUCLEASE

Bull semen ribonuclease, a basic protein with a molecular weight of 25,500, is similar to pancreatic ribonuclease A in regard to its specific activity (per μmole of enzyme) towards single‐stranded RNA, cytosine 2′ :3′‐phosphate and poly U, to its pH optimum in the action on single‐stranded RNA and to its inactivity towards double‐stranded DNA. It has been found, however, that this enzyme also degrades double‐stranded RNA, prepared from MS2 infected Escherichia coli cells, as well as the synthetic complex formed by poly A and poly U, under conditions where ribonuclease A has no appreciable effect. The pH optimum of the enzymatic activity on the substrates mentioned above appears to be around 7. The final products of the reaction with poly(A) · poly(U) have been shown to be uridine 3′‐phosphate and poly A. Copyright © 1969, Wiley Blackwell. All rights reserved