Lorber B, Giegé R, Ebel J P, Berthet C, Thierry J C, Moras D
J Biol Chem. 1983 Jul 10;258(13):8429-35.
A complex formed between the dimeric aspartyl-tRNA synthetase from yeast (Mr congruent to 125,000) and two molecules of its cognate yeast tRNAAsp (Mr = 24,160) was crystallized using ammonium sulfate as the precipitant. The crucial parameter which governs a successful crystallization is the enzyme tRNA stoichiometry. Crystals are only obtained when the starting solution precisely contains two tRNA molecules for one enzyme molecule. It was demonstrated by electrophoresis, biological activity assays, and crystallographic data that the crystals contain the two components in the same two to one stoichiometric ratio. The crystals, of cubic shape with edges up to 0.8 mm, belong to space group 1432. The cell parameter is 354 A and the asymmetric unit contains one particle of complex. The solvent content is about 78%, higher than the values commonly observed. Although particularly soft, the quality of the crystals is suitable for x-ray diffraction studies up to 7-A resolution.
利用硫酸铵作为沉淀剂，使来自酵母的二聚天冬氨酰 - tRNA合成酶（分子量约为125,000）与其两个同源酵母tRNAAsp分子（分子量 = 24,160）形成的复合物结晶。决定成功结晶的关键参数是酶与tRNA的化学计量比。只有当起始溶液中每个酶分子恰好含有两个tRNA分子时，才能获得晶体。通过电泳、生物活性测定和晶体学数据表明，晶体中这两种成分的化学计量比为二比一。晶体呈立方体形状，边长可达0.8毫米，属于空间群I432。晶胞参数为354 Å，不对称单元包含一个复合物颗粒。溶剂含量约为78%，高于通常观察到的值。尽管晶体特别软，但质量适合进行高达7 Å分辨率的X射线衍射研究。
