title: Bovine tryptophanyl-tRNA synthetase. A zinc metalloenzyme.
abstract: As is found by atomic absorption spectroscopy, the highly purified bovine tryptophanyl-tRNA synthetase contains up to 0.9 mol Zn2+/mol enzyme while some other bivalent metal ions are absent. The enzyme is inactivated either upon treatment with 1,10-phenanthroline (a zinc-chelating agent) or upon prolonged dialysis (which eliminates bound Zn2+ ions); addition of zinc reactivates the enzyme. Exposed histidine residue(s) and carboxylic group(s) of the enzyme are involved in the Zn2+ binding, as is shown using chemical modification. Circular dichroism spectra suggest that elimination of Zn2+ ions affects the tertiary rather than the secondary structure of the tryptophanyl-tRNA synthetase. The kinetics of inhibition with 1,10-phenanthroline toward ATP, tryptophan and tRNATrp indicates that removal of zinc prevents the ATP binding to the enzyme.
mesh_terms: D000604:Amino Acyl-tRNA Synthetases / Q000145:classification*; D000818:Animals; D002417:Cattle; D004789:Enzyme Activation; D008667:Metalloproteins / Q000145:classification*; D010179:Pancreas / Q000201:enzymology; D010618:Phenanthrolines / Q000494:pharmacology; D014369:Tryptophan-tRNA Ligase / Q000037:antagonists & inhibitors / Q000145:classification*; D015032:Zinc / Q000502:physiology*
chemical_list: D008667:Metalloproteins; D010618:Phenanthrolines; D000604:Amino Acyl-tRNA Synthetases; D014369:Tryptophan-tRNA Ligase; D015032:Zinc; C025205:1,10-phenanthroline