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. 2015 Jul 13;16(7):15872–15902. doi: 10.3390/ijms160715872

Figure 4.

Figure 4

Catalytic mechanism of aminoacylation by aminoacyl-tRNA synthetases. The top row represents the first step in which an aminoacyl adenylate intermediate is formed. In the second step, the “charged” aminoacyl-tRNA is formed. Binding of cognate tRNA is required for adenylate formation for GluRS, GlnRS, ArgRS, and LysRS-1 enzymes. Class II AARSs catalyze nucleophilic attack on the adenylate using the A76 3ʹ-hydroxyl; class I enzymes use the 2ʹ-OH for initial attack before transesterification to the 3ʹ-position.