The fragments from the 28 S ribosomal RNA of Galleria mellonella with unesterified uridine at the 3'-termini.

The three 3'-ends of the 28 S galleria RNA are all unesterified uridines. The two 18-S products due to the primary nick of the 28 S RNA have a similar 3'-terminal dinucleotide: G-Uoh. All of the seven species of secondary products from the Galleria 28 S RNA were suggested to have unesterified uridines, in common, at the 3'-ends. These results raise the possibility that the enzyme concerned in generating the primary and secondary nicks is a uracil-specific and 5'-phosphate-forming phosphodiesterase. The esterase, in association with the higher structure of the rRNA molecule in the larger subunit of the ribosome, probably determines the sites for these nicks in the 28 S rRNA. It is proposed also that the same enzyme can be responsible for cleaving the 28-S and 5.8-S rRNAs from their immediate precursor molecules.