Aminoacyl tRNA synthetase

From Free net encyclopedia

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.

Reaction:

  1. amino acid + ATP → aminoacyl-AMP + PPi
  2. aminoacyl-AMP + tRNA → aminoacyl-tRNA + AMP
[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.de:Aminoacyl-tRNA Synthetase

Retrieved from "http://www.netipedia.com/index.php/Aminoacyl_tRNA_synthetase"