Wu M X, Filley S J, Hill K A
Department of Biochemistry, Loma Linda University School of Medicine, California 92350.
Biochem Biophys Res Commun. 1994 Jun 30;201(3):1079-83. doi: 10.1006/bbrc.1994.1815.
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.
锌以每个酶亚基一克原子锌的化学计量比与来自大肠杆菌的四聚体丙氨酰 - tRNA合成酶结合。本文通过一系列平衡透析和内源荧光实验研究了这种金属 - 蛋白质相互作用的性质。透析数据表明，锌以协同方式与这种合成酶结合，在游离锌浓度为0.97微摩尔时达到最大锌结合量的一半，希尔系数为1.9。在锌诱导的蛋白质内源荧光猝灭中也观察到了协同特征，表明锌结合诱导了构象变化。这是关于锌与氨酰 - tRNA合成酶协同结合的首次报道，这些数据为丙氨酸特异性合成酶的寡聚结构提供了理论依据。
