An aminoacyl tRNA synthetase (abbreviated aaRs) is an enzyme that catalyzes the binding of a specific amino acid to a tRNA to form an aminoacyl-tRNA. The synthetase hydrolyzes ATP to bind the appropriate amino acid to the 3' hydroxyl of the tRNA molecule. It also mediates a proofreading reaction to ensure high fidelity of tRNA charging; if the tRNA is found to be improperly charged, the amino acid-tRNA bond is hydrolyzed. Ribbon diagram of the catalytically perfect enzyme TIM. Factor D enzyme crystal prevents the immune system from inappropriately running out of control. ... In chemistry, an amino acid is any molecule that contains both amino and carboxylic acid functional groups. ... Transfer RNA (abbreviated tRNA) is a small RNA chain (74-93 nucleotides) that transfers a specific amino acid to a growing polypeptide chain at the ribosomal site of protein synthesis during translation. ... Adenosine triphosphate (ATP) Adenosine triphosphate (ATP) is the nucleotide known in biochemistry as the molecular currency of intracellular energy transfer; that is, ATP is able to store and transport chemical energy within cells. ...
Reaction:
amino acid + ATP → aminoacyl-AMP + PPi
aminoacyl-AMP + tRNA → aminoacyl-tRNA + AMP
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. Aminoacylation is the process of adding an aminoacyl group to a compound. ... Aminoacylation is the process of adding an aminoacyl group to a compound. ...
An aminoacyltRNAsynthetase (aaRS) is an enzyme that catalyzes the esterification of a specific amino acid to its cognate tRNA to form an aminoacyl-tRNA.
The synthetase first binds ATP and the cognate amino acid to form an aminoacyl-adenylate and release inorganic pyrophosphate (PP i
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.
Class I aminoacyl-tRNA synthetases contain a characteristic Rossman fold and are mostly monomeric [ 2 ], while class II aminoacyl-tRNA synthetases share an anti-parallel beta-sheet formation, flanked by alpha-helices [ 3 ], and are mostly dimeric or multimeric.
The synthetases specific for alanine, asparagine, aspartic acid, glycine, histidine, lysine, phenylalanine, proline, serine, and threonine belong to class-II synthetases [ 4 ].
The 10 class I synthetases are considered to have in common the catalytic domain structure based on the Rossmann fold, which is totally different from the class II catalytic domain structure.
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