Table 1.

Table of division of aaRSs into classes.

Class I aaRSs	Class II aaRSs
ValRS, LeuRS, IleRS, CysRS,	SerRS, ThrRS, ProRS, GlyRS,
MetRS, ArgRS, GluRS, GlnRS,	HisRS, AspRS, AsnRS, PheRS,
TyrRS, TrpRS, LysRS I	AlaRS, LysRS II
	SepRS, PylRS, hmPheRS
Signature motifs
HIGH, KMSKS	motif 1, motif 2, motif 3
Architecture of catalytic domains
Rossmann fold	Antiparallel fold
Primary site of aminoacylation
2′-OH	3′-OH (except of PheRS)