Processing and Modification of tRNA Requires Several Enzymes

Processing and Modification of tRNA Requires Several Enzymes 

Transfer RNAs are processed from larger precursors in both prokaryotic and eukaryotic cells. This processing involves two types of nucleases Endoribonucleases, that cleave at internal sites in the RNA, and exonucleases, that remove nucleotides from the ends of the chains. 

The processing steps of E. coli tyrosine tRNATyr are diagrammed in figure 28.15. The initial transcript has, in addition to the 85 nucleotide residues of the final product, 41 residues at the 5 end and 225 residues at the 3 end it probably folds to form the typical cloverleaf structure of the mature tRNA prior to processing. Processing begins when a specific endonuclease called RNaseF cleaves the precursor 

Processing of E. coli ribosomal RNA. The ribosomal RNA is associated with these arrows. The various nucleases are described in 

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