Cooperative binding of zinc to an aminoacyl-tRNA synthetase.
Zinc binds to tetrameric alanyl-tRNA synthetase from Escherichia coli with a stoichiometry of one g-atom of zinc per enzyme subunit. The nature of this metal-protein interaction is investigated here through a series of equilibrium dialysis and intrinsic fluorescence experiments. The dialysis data show that zinc binds to this synthetase in a cooperative manner, with half-maximal zinc binding at 0.97 microM free zinc and a Hill coefficient of 1.9. The cooperative feature is also observed in the zinc-induced quenching of the protein intrinsic fluorescence, indicating that zinc binding induces a conformational change. This is the first report of cooperative binding of zinc to an aminoacyl-tRNA synthetase, and the data provide a rationale for the oligomeric structure of the synthetase specific for alanine.
Department of Biochemistry, Loma Linda University School of Medicine, California 92350.
M X
MX
Wu
S J
SJ
Filley
K A
KA
Hill
D000412:Alanine-tRNA Ligase / Q000378:metabolism*; D001426:Bacterial Proteins; D004926:Escherichia coli; D008667:Metalloproteins / Q000378:metabolism*; D011485:Protein Binding; D013050:Spectrometry, Fluorescence; D015032:Zinc / Q000378:metabolism*
D001426:Bacterial Proteins; D008667:Metalloproteins; D000412:Alanine-tRNA Ligase; D015032:Zinc