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. 2008 Dec 4;105(49):19031–19032. doi: 10.1073/pnas.0810781106

Fig. 1.

Fig. 1.

Pretransfer and posttransfer editing of noncognate amino acids by aminoacyl-tRNA synthetases. The amino acid (AA) is activated in an ATP-dependent reaction at the active site (AS) to form an enzyme-bound aminoacyl-adenylate (AA-AMP). In pretransfer editing, AA-AMP is hydrolyzed directly, thereby preventing the synthesis of a noncognate aminoacyl-tRNA. In posttransfer editing, AA-AMP is a substrate for esterification of the 3′ end of the tRNA, which then translocates to the editing site (ES) where the AA is removed. PPi, pyrophosphate.