Conserved amino acids near the carboxy terminus of bacterial tyrosyl-tRNA synthetase are involved in tRNA and Tyr-AMP binding

Bacterial tyrosyl-tRNA synthetases occur in two large subfamilies, TyrRS an d TyrRZ, that possess about 250/u amino acid identity. Their amino-terminal region, the active site domain, is more conserved (>36% identity). The car boxyterminal segment of these enzymes includes the tRNA binding domain and contains only few conserved residues. Replacement of three of these residue s in in Acidithiobacillus ferrooxidans TyrRZ revealed that S356 and K395 pl ay roles in tRNA binding, while H306, a residue at the junction of the cata lytic and tRNA binding domains, stabilizes the Tyr-AMP:TyrRZ complex. The r eplacement data suggest that conserved amino acids in A. ferrooxidans TyrRZ and Bacillus stearothermophilus TyrRS play equivalent roles in enzyme func tion. (C) 2001 Federation of European Biochemical Societies. Published by E lsevier Science B.V. All rights reserved.