Biosynthesis of transfer RNA: in vitro conversion of transfer RNA precursors from Bombyx mori to 4S RNA by Escherichia coli enzymes.

Evidence for the presence of rapidly labeled short-lived RNA species, presumed to be precursors to transfer RNA (tRNA), in the silk glands of Bombyx mori is presented. These precursors, which migrate between 4S and 5S markers on acrylamide gels, can be converted in vitro into molecules indistinguishable in size from tRNA. The conversion is also catalyzed by a crude enzyme fraction isolated from ribosomes of E. coli. Since a similar enzyme preparation cleaves the suppressor tRNA(Tyr) sequence of E. coli from its precursor molecule, it would appear that the precursor to E. coli tRNA(Tyr) and the precursors to silk-gland tRNAs share common structural features.