tRNA nucleotidyltransferase

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tRNA nucleotidyltransferase
1r6m.jpg
RNase PH hexamer, Pseudomonas aeruginosa
Identifiers
EC number2.7.7.56
CAS number116412-36-3
Databases
IntEnzIntEnz view
BRENDABRENDA entry
ExPASyNiceZyme view
KEGGKEGG entry
MetaCycmetabolic pathway
PRIAMprofile
PDB structuresRCSB PDB PDBe PDBsum
Gene OntologyAmiGO / QuickGO

In enzymology, a tRNA nucleotidyltransferase (EC 2.7.7.56) is an enzyme that catalyzes the chemical reaction

tRNAn+1 + phosphate tRNAn + a nucleoside diphosphate

where tRNA-N is a product of transcription, and tRNA Nucleotidyltransferase catalyzes this cytidine-cytidine-adenosine (CCA) addition to form the tRNA-NCCA product.

Function[edit]

Protein synthesis takes place in cytosolic ribosomes, mitochondria (mitoribosomes), and in plants, the plastids (chloroplast ribosomes). Each of these compartments requires a complete set of functional tRNAs to carry out protein synthesis. The production of mature tRNAs requires processing and modification steps[1] such as the addition of a 3’-terminal cytidine-cytidine-adenosine (CCA). Since no plant tRNA genes encode this particular sequence, a tRNA nucleotidyltransferase must add this sequence post-transcriptionally and therefore is present in all three compartments.

In eukaryotes, multiple forms of tRNA nucleotidyltransferases are synthesized from a single gene and are distributed to different subcellular compartments in the cell. There are multiple in-frame start codons which allow for the production of variant forms of the enzyme containing different targeting information predominantly found in the N-terminal sequence of the protein (reference). In vivo experiments show that the N-terminal sequences are used as transit peptides for import into the mitochondria and plastids. Comparison studies using available tRNA nucleotidyltransferase sequences have identified a single gene coding for this enzyme in plants. Complementation studies in yeast using cDNA derived from Arabidopsis thaliana[2] or Lupinus albus genes[3] demonstrate the biological activity of these enzymes. The enzyme has also been shown to repair damaged or incomplete CCA sequences in yeast.[4]

This enzyme belongs to the family of transferases, specifically those transferring phosphorus-containing nucleotide groups (nucleotidyltransferases).

References[edit]

  1. ^ Hopper AK, Phizicky EM (January 2003). "tRNA transfers to the limelight". Genes Dev. 17 (2): 162–80. doi:10.1101/gad.1049103. PMID 12533506.
  2. ^ Gu J (2000). Identification of proteins interacting with lupin and Arabidopsis tRNA nucleotidyltransferase (MSc). Concordia University, Canada. pp. 51–55.
  3. ^ Shanmugam K, Hanic-Joyce PJ, Joyce PB (January 1996). "Purification and characterization of a tRNA nucleotidyltransferase from Lupinus albus and functional complementation of a yeast mutation by corresponding cDNA". Plant Mol. Biol. 30 (2): 281–95. doi:10.1007/bf00020114. PMID 8616252.
  4. ^ Rosset R, Monier R (November 1965). "[Instability of the terminal 3'-hydroxy sequence of transfer RNA in microorganisms. I. Turnover of terminal AMP in Saccharomyces cerevisiae]". Biochim. Biophys. Acta (in French). 108 (3): 376–84. doi:10.1016/0005-2787(65)90030-4. PMID 4286478.

Further reading[edit]