Aminoacyl tRNA Synthetase

Aminoacyl tRNA synthetase (aaRS) or aminoacyl tRNA ligase catalyzes the esterification of a specific amino acid to its cognate tRNA to form an aminoacyl-tRNA. The amino acid is transferred by the ribosome from the aminoacylated-tRNA onto a growing polypeptide chain. Class I of aaRS is a monomer or dimer, it has 2 highly conserved sequence motifs and it aminoacylates at the 2’-OH of an adenosine nucleotide. Class II of aaRS is a dimer or tetramer, it has 3 highly conserved sequence motifs and it aminoacylates at the 3’-OH of an adenosine nucleotide. CP1 domain of RS edits a mischarged aa-tRNA. Some of the crystal structures are complexes of the RS with their reactant analog: amino acid-sulfamoyl adenine (aa-SA).^[1].

• For leucine-RS details see Leucyl-tRNA Synthetase.
• For pyrrolysyl-RS of pyrrolysine-tRNA ligase details see Pyrrolysyl-tRNA synthetase.

3D Structures of Aminoacyl tRNA synthetase

Aminoacyl tRNA synthetase 3D structures

One very interesting question in biology is how does an aminoacyl-tRNA synthetase recognize a particular tRNA and charge it with the correct amino acid? This is a challenging problem, since all tRNAs have the same general structure. Interestingly, different tRNA synthetases accomplish this goal in different ways.

The (GlnRS) interacts with both . Genetic and biochemical data indicate that GlnRS interacts with all three bases of the , which are unstacked and splay outward so they can bind in separate recognition pockets of GlnRS. The 3' end of tRNAgln plunges deeply into a protein pocket that also binds the enzyme's and glutamine substrates.