ABSTRACT
Transfer ribonucleic acid (tRNA) molecules play an important role in protein synthesis. Each tRNA becomes covalently bonded to a specific amino acid to form aminoacyl-tRNA which recognizes the corresponding codon in messanger RNA and ensures that the correct amino acid is added to the growing polypeptide chain. The ribosomal RNA (rRNA) transcription units in E. coli contain some tRNA genes that are transcribed and processed at the time of rRNA transcription. As in prokaryotes, several tRNAs may be transcribed together to yield a single pre-tRNA molecule that is then processed to release the mature tRNAs. Transfer RNA molecules are notable for containing unusual nucleotides such as 1-methylguanosine, pseudouridine, dihydrouridine, inosine and 4-thiouridine. These are created by modification of guanosine and uridine after tRNA synthesis. The three dimensional structure of tRNA is even more complex because of additional interactions between the various units of secondary structure.
