Aminoacyl tRNA synthetase

From Wikipedia, the free encyclopedia

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:

  1. amino acid + ATP → aminoacyl-AMP + PPi
  2. aminoacyl-AMP + tRNA → aminoacyl-tRNA + AMP

Sum of 1 and 2: amino acid + tRNA + ATP → aminoacyl-tRNA + AMP + PPi

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.

v • d • e
Proteins: enzymes

Active site - Binding site - Catalytically perfect enzyme - Coenzyme - Cofactor - EC number - Enzyme catalysis - Enzyme kinetics - Enzyme inhibitor - Lineweaver-Burk plot - Michaelis-Menten kinetics

EC1 Oxidoreductases,O+R+D/list (alcohol oxidoreductases, CH-CH oxidoreductases, peroxidase, oxygenase) - EC2 Transferases/list (methyltransferase, acyltransferase, glycosyltransferase, transaminase, phosphotransferase, polymerase, kinase) - EC3 Hydrolases/list (esterase, DNA glycosylases, glycosidase, protease, acid anhydride hydrolases) - EC4 Lyases/list (carboxy-lyases, aldolase, dehydratase, synthase, adenylate cyclase, guanylate cyclase) - EC5 Isomerases/list (mutase, topoisomerase) - EC6 Ligases/list (DNA ligase, aminoacyl tRNA synthetase)

v • d • e
Protein biosynthesis: translation (prokaryotic, eukaryotic)

Ribosomal proteins: Initiation factor (Prokaryotic, Eukaryotic) - Elongation factor (Prokaryotic, Eukaryotic) - Release factor (Prokaryotic, Eukaryotic) - Ribosomal protein S6 kinase

Aminoacyl tRNA synthetase - Reading frame - Start codon - Shine-Dalgarno sequence/Kozak consensus sequence

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