Target type: biologicalprocess
The process in which the 3' end of a pre-tRNA molecule is converted to that of a mature tRNA. [GOC:go_curators]
tRNA 3'-end processing is a crucial step in tRNA biogenesis, ensuring the correct structure and function of these essential molecules. The process involves a series of enzymatic reactions that trim the 3' end of the tRNA precursor, add a CCA sequence, and modify the terminal adenosine residue.
**1. Pre-tRNA 3' End Processing:**
- The initial tRNA transcript, known as pre-tRNA, has a 3' extension beyond the mature tRNA sequence.
- This extension is removed by an exonuclease, typically RNase Z in eukaryotes and bacteria.
- RNase Z recognizes a specific sequence at the 3' end of the pre-tRNA and cleaves the transcript, leaving a 5'-hydroxyl group at the newly formed 3' end.
**2. CCA Addition:**
- After trimming, the tRNA molecule lacks the essential CCA sequence at the 3' end.
- This sequence is added by a dedicated enzyme called tRNA nucleotidyltransferase (or CCA-adding enzyme).
- The enzyme adds the three nucleotides (cytosine, cytosine, adenosine) in a template-independent manner, utilizing ATP, CTP, and ATP as substrates.
- The CCA sequence is essential for tRNA function as it serves as the amino acid acceptor site and is recognized by aminoacyl-tRNA synthetases.
**3. Terminal Adenosine Modification:**
- The terminal adenosine (A76) of the CCA sequence is often modified by the addition of a 3' - 3'-linked cytidine residue (C76).
- This modification, catalyzed by tRNA nucleotidyltransferase, enhances the efficiency of tRNA aminoacylation.
- In some cases, A76 can also be modified by the addition of a 3' - 5' linked cytidine residue (C76) by the enzyme tRNA-specific CCA-adding enzyme.
**4. Quality Control:**
- Throughout the processing steps, quality control mechanisms ensure the correct and efficient processing of tRNA molecules.
- This includes surveillance mechanisms that detect and eliminate misprocessed or damaged tRNA transcripts, preventing the accumulation of non-functional tRNA molecules.
**In summary, tRNA 3'-end processing is a precisely regulated and essential step in tRNA biogenesis, ensuring the production of mature and functional tRNA molecules that are critical for protein synthesis.**'
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| Protein | Definition | Taxonomy |
|---|---|---|
| Ribonuclease T | A ribonuclease T that is encoded in the genome of Escherichia coli K-12. [PRO:DNx, UniProtKB:P30014] | Escherichia coli K-12 |
| Compound | Definition | Classes | Roles |
|---|---|---|---|
| citric acid, anhydrous | citric acid : A tricarboxylic acid that is propane-1,2,3-tricarboxylic acid bearing a hydroxy substituent at position 2. It is an important metabolite in the pathway of all aerobic organisms. Citric Acid: A key intermediate in metabolism. It is an acid compound found in citrus fruits. The salts of citric acid (citrates) can be used as anticoagulants due to their calcium chelating ability. | tricarboxylic acid | antimicrobial agent; chelator; food acidity regulator; fundamental metabolite |
| aurintricarboxylic acid | aurintricarboxylic acid : A member of the class of quinomethanes that is 3-methylidene-6-oxocyclohexa-1,4-diene-1-carboxylic acid in which the methylidene hydrogens are replaced by 4-carboxy-3-hydroxyphenyl groups. The trisodium salt is the biological stain 'chrome violet CG' while the triammonium salt is 'aluminon'. Aurintricarboxylic Acid: A dye which inhibits protein biosynthesis at the initial stages. The ammonium salt (aluminon) is a reagent for the colorimetric estimation of aluminum in water, foods, and tissues. | monohydroxybenzoic acid; quinomethanes; tricarboxylic acid | fluorochrome; histological dye; insulin-like growth factor receptor 1 antagonist |
| dithionitrobenzoic acid | dithionitrobenzoic acid : An organic disulfide that results from the formal oxidative dimerisation of 2-nitro-5-thiobenzoic acid. An indicator used to quantify the number or concentration of thiol groups. Dithionitrobenzoic Acid: A standard reagent for the determination of reactive sulfhydryl groups by absorbance measurements. It is used primarily for the determination of sulfhydryl and disulfide groups in proteins. The color produced is due to the formation of a thio anion, 3-carboxyl-4-nitrothiophenolate. | nitrobenzoic acid; organic disulfide | indicator |
| 7-nitro-1h-indole-2-carboxylic acid | 7-nitro-1H-indole-2-carboxylic acid: acts on AP endonuclease, 3'-phosphodiesterase, and 3'-phosphatase activities of APE1; structure in first source |