In enzymology , a tRNA nucleotidyltransferase ( EC 2.7.7.56 ) is an enzyme that catalyzes the chemical reaction
5-578: RNase PH is a tRNA nucleotidyltransferase , present in archaea and bacteria , that is involved in tRNA processing. Contrary to hydrolytic enzymes, it is a phosphorolytic enzyme, meaning that it uses inorganic phosphate as a reactant to cleave nucleotide-nucleotide bonds, releasing diphosphate nucleotides . The active structure of the proteins is a homohexameric complex, consisting of three ribonuclease (RNase) PH dimers. RNase PH has homologues in many other organisms, which are referred to as RNase PH-like proteins. The part of another larger protein with
10-528: A domain that is very similar to RNase PH is called an RNase PH domain (RPD). Two highly related exoribonuclease complexes: This genetics article is a stub . You can help Misplaced Pages by expanding it . TRNA nucleotidyltransferase where tRNA-N is a product of transcription, and tRNA Nucleotidyltransferase catalyzes this cytidine-cytidine-adenosine (CCA) addition to form the tRNA-NCCA product. Protein synthesis takes place in cytosolic ribosomes , mitochondria (mitoribosomes), and in plants,
15-459: 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
20-439: 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 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
25-457: The protein. 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 or Lupinus albus genes demonstrate
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