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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
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.
External links[]
Proteins: enzymes | |
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Topics |
Active site - Allosteric regulation - Binding site - Catalytically perfect enzyme - Coenzyme - Cofactor - Cooperativity - EC number Enzyme 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) | |||||||||||||||||||||||||||
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Ribosomal proteins |
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Other concepts |
Aminoacyl tRNA synthetase · Reading frame · Start codon · Stop codon · Shine-Dalgarno sequence/Kozak consensus sequence | ||||||||||||||||||||||||||
see also disorders of translation and posttranslational modification Template:Protein biosynthesis navs |
- de:Aminoacyl-tRNA-Synthetase
- ja:アミノアシルtRNAシンセテース
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