抄録
Prokaryotic tRNATrp and tRNAPhe and some other tRNAs seem to well conserve primitive tRNA (proto-tRNA) commonly ancestral to all contemporary tRNAs. The 5'-and 3'-halves of the E. coli (EC) tRNATrp and the Bacillus svbtilis (BSU) tRNAPhe were aligned with one another, resulting in a finding that proto-tRNA first emerged via duplication of ca. 38-base-long semi-tRNA which had (5') CCA (3') in its 3'-terminus. The peptidyltransferase (PT) region (bases 2469-2589) of 23S rRNA was found to be a close homologue of contemporary 5S rRNA (EC) showing a 54.4% base-match and a matching probability by chance, Pnuc(62, 114)=0.21×10-10. This well coinsides with Noller et al's (1992) recent experimental result that large-subunit rRNA has a PT activity. U1 snRNA and some possibly primitive mRNAs also showed significant levels of base sequence similarity, suggesting that some snRNAs and primitive mRNAs most probably emerged from tRNA-like or semi-tRNA-like primitive RNA (s).
