NUCLEOSIDE TRIPHOSPHATASE-ACTIVITY ASSOCIATED WITH THE N-TERMINAL DOMAIN OF MAMMALIAN TRYPTOPHANYL-TRANSFER-RNA SYNTHETASE

Bovine tryptophanyl-tRNA synthetase (EC 6.1.1.2) deprived of Zn2+ by c helation with the phosphonate analog of Ap(4)A hydrolized ATP(GTP) to ADP(GDP) although its ability to form tryptophanyl adenylate was impai red. This hydrolytic activity is stimulated by Mg2+ and Mn2+ ions and inhibited by Zn2+. Monoclonal antibody Aml against the N-terminal doma in of the enzyme completely abolished ATP(GTP)ase activity. The core p eptide generated after proteolytic splitting of the N-domain lacks thi s activity. We suggest that the nucleotide binding site(s) different f rom ATP sites involved in aminoacylation reaction reside(s) at the N-t erminal domain(s) of the enzyme.