6.1.1.21	ATP + L-histidine + tRNAHis = AMP + diphosphate + L-histidyl-tRNAHis	-	-	
6.1.1.21	ATP + L-histidine + tRNAHis = AMP + diphosphate + L-histidyl-tRNAHis	2-step mechanism, elucidation of structure-activity relationship, the N-terminal catalytic domain contains the six-stranded antiparallel beta-sheet and the three motifs characteristics of class II aaRS, a HisRS-specific helical domain inserted between motifs 2 and 3 that may contact the acceptor stem of the tRNA, a C-terminal alpha/beta domain may be involved in the recognition of the anticodon stem and loop of tRNAHis	650438	
6.1.1.21	ATP + L-histidine + tRNAHis = AMP + diphosphate + L-histidyl-tRNAHis	interaction mechanism of RNA substrate and enzyme, active site structure	650256	
6.1.1.21	ATP + L-histidine + tRNAHis = AMP + diphosphate + L-histidyl-tRNAHis	mechanism, active site structure, ligand induced structural changes, highly cooperative dynamics	649862	
6.1.1.21	ATP + L-histidine + tRNAHis = AMP + diphosphate + L-histidyl-tRNAHis	N73 is a discriminator base involved in histidylation activity, substrate recognition mechanism	653611	
6.1.1.21	ATP + L-histidine + tRNAHis = AMP + diphosphate + L-histidyl-tRNAHis	relation between the conservation of active site residues and the molecular mechanism of aminoacylation reaction, relevant reaction coordinate and the orientation of the catalytic residue, Arg259, model of active site with the substrates, Mg2+ ions and water, overview. Calculation of the transition state structures of the activation step of aminoacylation reaction using the combined ab-initio/semi-empirical calculation	714477	
6.1.1.21	ATP + L-histidine + tRNAHis = AMP + diphosphate + L-histidyl-tRNAHis	substrate-assisted concerted mechanism, rate of aminoacyl transfer is independent of the interaction between the carboxamide group of Q127 and the alpha-carboxylate carbon	661192	
6.1.1.21	ATP + L-histidine + tRNAHis = AMP + diphosphate + L-histidyl-tRNAHis	the major groove amine of C73 and the 6-keto oxygen of G-1 of tRNAHis participate in hydrogen bonding with histidine-tRNA ligase, while the 5'-monophosphate provides necessary electrostatic interactions with the positive residues of enzyme active site	661936	
6.1.1.21	ATP + L-histidine + tRNAHis = AMP + diphosphate + L-histidyl-tRNAHis	two molecules of ATP and histidine are bound per molecule of enzyme	369