Translational System
Overview
Translational Mechanism and amber-codon
tRNA/aminoacyl-synthetase
The class I synthetases are monomeric synthetases and feature all structurally similar active site Rossmann fold domains in the region of the N-terminal. Beside this region, there are no significant structural or sequence similarities among the class I enzymes.
There is an acceptor binding site inserted into the Rossmann-fold domain at a common location which binds the single stranded terminal end of the tRNA, while its C-terminal domain binds in the minor groove of the L-shaped tRNA and the anticodon arm. That is the point for the discrimination among the different tRNAs. The binding requires the formation of a hairpin structure of the single stranded 3’-terminus with the amino acid and the ATP in the active site (Chang et al., 2010, Krebs et al., 2014).
Figure 1: Crystal structure of a class I tRNA/aminoacyl synthetase.
The tRNA is shown in red and the protein i n blue (Krebs et al., 2014).