Deutscher M P, Ni R C
J Biol Chem. 1982 Jun 10;257(11):6003-6.
Mammalian aminoacyl-tRNA synthetases are often found in several different molecular weight forms in the same extract, although the structural basis for this diversity is not clear. In this report, we describe the separation of high and low molecular weight forms of rat liver arginyl-tRNA synthetase, and the extensive purification to near homogeneity of the low molecular weight form of the enzyme, free of other aminoacyl-tRNA synthetases. The purified enzyme catalyses the incorporation into tRNA of 9,500 nmol of arginine/min/mg of protein under optimal assay conditions, corresponding to a turnover number of approximately 550 min-1. The molecular weight of the native enzyme was calculated to be approximately 59,000 based on a sedimentation coefficient of about 3.6 S and a Stokes radius of 39 A. The subunit molecular weight based on sodium dodecyl sulfate-acrylamide gel electrophoresis was also about 60,000, indicating that the enzyme is a monomer. The relation of this form of arginyl-tRNA synthetase to the high molecular weight form and its possible origin are discussed.
在同一提取物中，哺乳动物氨酰 - tRNA合成酶常常以几种不同分子量的形式存在，尽管这种多样性的结构基础尚不清楚。在本报告中，我们描述了大鼠肝脏精氨酰 - tRNA合成酶高分子量和低分子量形式的分离，以及将该酶的低分子量形式广泛纯化至接近均一，且不含其他氨酰 - tRNA合成酶。在最佳测定条件下，纯化后的酶催化每分钟每毫克蛋白质将9500 nmol精氨酸掺入tRNA，相应的转换数约为550 min⁻¹。基于约3.6 S的沉降系数和39 Å的斯托克斯半径，计算出天然酶的分子量约为59,000。基于十二烷基硫酸钠 - 丙烯酰胺凝胶电泳的亚基分子量也约为60,000，表明该酶是单体。本文讨论了这种形式的精氨酰 - tRNA合成酶与高分子量形式的关系及其可能的来源。
