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#CCA sequence

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Processing of rRNA and tRNA

CCA sequence at 3′ end of tRNA is added by

All mature tRNAs require conserved CCA terminal trinucleotide at 3' end where amino acid attaches via ester linkage. In most bacteria and eukaryotes, CCA is absent from tRNA gene and added post-transcriptionally by ATP(CTP):tRNA nucleotidyltransferase, CCA-adding enzyme. This enzyme binds T-loop and acceptor stem, sequentially polymerizing C-C-A using CTP and ATP. It also surveys tRNA quality, adding CCA to correctly folded tRNAs and engaging in repair cycles where damaged termini are excised and resynthesized, ensuring translational competence. This refined regulation supports accurate riboso

Ref: Watson et al., Molecular Biology of the Gene, 7th ed., Chapter 15, tRNA nucleotidyltransferase CCA-adding enzyme

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Processing of mRNA, rRNA, tRNA

CCA sequence at 3' end of tRNA is added by

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

Ref: Lodish et al., Molecular Cell Biology, 9th ed., Chapter 11: CCA-adding enzyme adds CCA; Berg et al., Biochemistry, CCA nucleotidyltransferase mechanism

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