Structures
Both classes of aminoacyl-tRNA synthetases are multidomain proteins. In a typical scenario, an aaRS consists of a catalytic domain (where both the above reactions take place) and an anticodon binding domain (which interacts mostly with the anticodon region of the tRNA and ensures binding of the correct tRNA to the amino acid). In addition, some aaRSs have additional RNA binding domains and editing domains that cleave incorrectly paired aminoacyl-tRNA molecules.
The catalytic domains of all the aaRSs of a given class are found to be homologous to one another, whereas class I and class II aaRSs are unrelated to one another. The class I aaRSs have the ubiquitous Rossmann fold and have the antiparallel beta-strands architecture, whereas the class II aaRSs have a unique fold made up of antiparallel beta-strands.
The alpha helical anticodon binding domain of Arginyl, Glycyl and Cysteinyl-tRNA synthetases is known as the DALR domain after characteristic conserved amino acids.
Read more about this topic: Aminoacyl TRNA Synthetase
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