title: [Role of zinc ions in the functioning of bovine tryptophanyl-tRNA-synthetase].
abstract: By means of atomic absorption spectroscopy up to 0.9 Zn2+ atom per molecule of bovine tryptophanyl-tRNA-synthetase (E. C. 6.1.1.2) was found. Treatment of the enzyme with orthophenanthroline (Zn2+-chelating agent) or prolonged dialysis leading to the removal of bound Zn2+ causes inactivation of the enzyme whereas the addition of Zn2+ reactivates it. Kinetic analysis of the inhibiting action of orthophenanthroline at various concentrations of tryptophan, ATP and tRNA leads to the conclusion that removal of Zn2+ prevents the binding of the ATP molecule to tryptophanyl-tRNA-synthetase. By means of chemical modification it is shown that exposed histidine residues and the carboxylic groups of the enzyme participate in Zn2+ binding. According to circular dichroism data removal of Zn2+ has no influence on the secondary structure although some local alterations of the ternary structure are revealed.
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D000604:Amino Acyl-tRNA Synthetases / Q000502:physiology*; D000818:Animals; D002417:Cattle; D007700:Kinetics; D010179:Pancreas / Q000201:enzymology*; D010618:Phenanthrolines / Q000494:pharmacology; D011485:Protein Binding; D011487:Protein Conformation; D013054:Spectrophotometry, Atomic; D014369:Tryptophan-tRNA Ligase / Q000037:antagonists & inhibitors / Q000502:physiology*; D015032:Zinc / Q000502:physiology*
chemical_list: D010618:Phenanthrolines; D000255:Adenosine Triphosphate; D000604:Amino Acyl-tRNA Synthetases; D014369:Tryptophan-tRNA Ligase; D015032:Zinc; C025205:1,10-phenanthroline
vernacular_title: Rol' ionov tsinka v funktsionirovanii triptofanil-tRNK-sintetazy krupnogo rogatogo skota.