Practice question

Mature transfer RNAs require universal CCA sequence at three prime terminus with terminal adenosine bearing amino acid attachment via ester linkage to two prime or three prime hydroxyl. In many eukaryotic genes, particularly vertebrate mitochondrial transfer RNAs, CCA not encoded and must be added post-transcriptionally. CCA-adding enzyme, member of class two nucleotidyltransferase beta-nucleotidyltransferase family, acts template-independently, sequentially adding cytidine, cytidine, adenosine using CTP and ATP as substrates while proofreading. Enzyme uses single active site with flexibility accommodating CTP versus ATP, flipping tRNA acceptor stem after each addition. Activity essential for translation fidelity.