A Cleavage Site of Ribonuclease F

A new endoribonuclease activity, RNase F, was partially purified from Escherichia coli cells. This activity can specifically cleave a precursor RNA molecule (of species 1) isolated from T4‐infected cells [N. Watson & D. Apirion (1981) Biochem. Biophys. Res. Commun. 103, 543–551], The cleavage results in products which are very similar to RNA molecules found in the cell, generating a 3′‐phosphate and a 5′‐hydroxyl groups. The cleavage takes place between a cytosine and an adenine moiety, within a possible loop and stem structure; the cut is in the border between the double‐stranded and single‐stranded regions of this structure. The specificity of this enzyme could be the introduction of a cleavage near the 3′ ends o f tRNA molecules and other RNAs like species 1 which could resemble tRNA in their three‐dimensional structure.