Figure 3. tRNA that carries alanine.

Figure 4. Mechanism for amino acyl tRNA synthetase-the enzyme that catalyzes the attachment of an amino acid to tRNA

• Figure 4 shows the mechanism for the attachment of an amino acid in tRNA.
  
  
• In the first step, the CO2- of amino acid attacks the a-phosphorus of ATP. The carboxylic acid of amino acid is now activated with good leaving group.
  
  
• The 3’-OH group of tRNA attacks the carbonyl carbon via nucleophilic addition to give the amino acid attached tRNA.