Fine structure of RNA codewords recognized by bacterial, amphibian, and mammalian transfer RNA.

Nucleotide sequences of 50 RNA codons recognized by amphibian and mammalian liver transfer RNA preparations were determined and compared with those recognized by Escherichia coli transfer RNA. Almost identical translations were obtained with transfer RNA from guinea pig liver, Xenopus laevis liver (South African clawed toad), and E. coli. However, guinea pig and Xenopus transfer RNA differ markedly from E. coli transfer RNA in relative response to certain trinucleotides. Transfer RNA from mammalian liver, amphibian liver, and amphibian muscle respond similarly to trinucleotide codons. Thus the genetic code is essentially universal, but transfer RNA from one organism may differ from that of another in relative response to some codons.