Aminoacyl tRNA synthetase
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An aminoacyl tRNA synthetase (aaRS) is an enzyme that catalyzes the esterification of a specific amino acid to one of all its compatible cognate tRNAs to form an aminoacyl-tRNA. The synthetase first binds ATP and the cognate amino acid to form an aminoacyl-adenylate and release inorganic pyrophosphate (PPi). The adenylate-aaRS complex then binds the appropriate tRNA molecule, and the amino acid is transferred from the aa-AMP to either the 2'- or 3'-OH of the last tRNA base (A76) at the 3'-end. Some synthetases also mediate a proofreading reaction to ensure high fidelity of tRNA charging; if the tRNA is found to be improperly charged, the aminoacyl-tRNA bond is hydrolyzed.
Reaction:
- amino acid + ATP → aminoacyl-AMP + PPi
- aminoacyl-AMP + tRNA → aminoacyl-tRNA + AMP
Sum of 1 and 2: amino acid + tRNA + ATP → aminoacyl-tRNA + AMP + PPi
[edit] Classes
There are two classes of aminoacyl tRNA synthetase:
- Class I has two common homologous peptide sequence motifs. It aminoacylates at the 2'-OH.
- Class II has three common homologous peptide sequence motifs. It aminoacylates at the 3'-OH.
The one exception to the above rule is PheRS, a class II enzyme that attaches Phenylalanine to the 2'-OH of tRNAPhe.
[edit] External links
Proteins: enzymes | |
|---|---|
| Topics | Active site - Allosteric regulation - Binding site - Catalytically perfect enzyme - Coenzyme - Cofactor - Cooperativity - EC numberEnzyme catalysis - Enzyme inhibitor - Enzyme kinetics - Lineweaver-Burk plot - Michaelis-Menten kinetics - List of enzymes |
| Types | EC1 Oxidoreductases/list - EC2 Transferases/list - EC3 Hydrolases/list - EC4 Lyases/list - EC5 Isomerases/list - EC6 Ligases/list |
Protein biosynthesis: translation (prokaryotic, eukaryotic) | |
|---|---|
| Ribosomal proteins | Initiation factor (Prokaryotic, Eukaryotic) -
Elongation factor (Prokaryotic, Eukaryotic) - Release factor (Prokaryotic, Eukaryotic) - Ribosomal protein s6 |
| Other concepts | Aminoacyl tRNA synthetase - Reading frame - Start codon - Shine-Dalgarno sequence/Kozak consensus sequence |
- de:Aminoacyl-tRNA-Synthetase
- ja:アミノアシルtRNAシンセテース
| This page uses content from the English-language version of Wikipedia. The original article was at Aminoacyl tRNA synthetase. The list of authors can be seen in the page history. As with Psychology Wiki, the text of Wikipedia is available under the GNU Free Documentation License. |
