7 MAMMALIAN AMINOACYL-TRANSFER RNA-SYNTHETASES ASSOCIATED WITHIN THE SAME COMPLEX ARE FUNCTIONALLY INDEPENDENT
7 MAMMALIAN AMINOACYL-TRANSFER RNA-SYNTHETASES ASSOCIATED WITHIN THE SAME COMPLEX ARE FUNCTIONALLY INDEPENDENT
复制标题
DOI：
10.1111/j.1432-1033.1983.tb07244.x
复制
发表时间：
1983-01-01
期刊：
影响因子：
--
通讯作者：
WALLER, JP
中科院分区：
文献类型：
--
作者：
MIRANDE, M;CIRAKOGLU, B;WALLER, JP
对绵羊肝脏中含有7种异亮氨酸、亮氨酸、蛋氨酸、谷氨酰胺、谷氨酸、赖氨酸和精氨酸的氨基酰tRNA合成酶的异型多酶复合体进行了动力学分析。这项研究是为了研究这些酶的联合可能会赋予不同于它们不相关的对应酶的动力学性质的可能性。通过两种不同的方法获得的证据导致了相关酶在功能上独立的结论。首先，该复合体的甲硫基-tRNA和赖氨酰-tRNA合成酶组分的动力学常数与控制蛋白分解后得到的非结合组分的动力学常数没有显著差异。其次，该复合体的甲硫酰-tRNA合成酶组分显示出相同的动力学常数；无论是在单独存在[14C]蛋氨酸、三磷酸腺苷和高度浓缩的tRNAMet的情况下，还是在其他6种酶形成未标记的氨基酰-tRNA所需的底物存在的情况下，都是如此。同样，由其他6种酶中的任何一种催化的[14C]氨基酰-tRNA合成的初始速率不受其他氨酰-tRNA合成酶的伴随功能的影响。在tRNA氨酰化分析中占主导地位的条件下，复合体的氨酰基-tRNA合成酶成分的沉降行为表明，在这些条件下，它们仍然是关联的。讨论了这些发现对复合体内酶的结构组织的影响。
A heterotypic multienzyme complex from sheep liver containing 7 aminoacyl-tRNA synthetases specific for isoleucine, leucine, methionine, glutamine, glutamic acid, lysine and arginine was subjected to kinetic analyses. The study was undertaken to examine the possibility that association of these enzymes may impart kinetic properties which differ from those of their unassociated counterparts. The evidence obtained by 2 different approaches leads to the conclusion that the associated enzymes are functionally independent. Firstly, the kinetic constants of the methionyl-tRNA and lysyl-tRNA sythetase components of the complex do not differ significantly from those of their unassociated counterparts obtained after controlled proteolysis of the complex. Secondly, the methionyl-tRNA synthetase component of the complex displays identical kinetic constants; this is true whether assayed in the presence of [14C]methionine, ATP and highly enriched tRNAMet alone, or in the additional presence of the substrates required for unlabeled aminoacyl-tRNA formation by each of the other 6 enzymes. Similarly, the initial rates of [14C]aminoacyl-tRNA formation catalyzed by any of the 6 other enzymes were unaffected by the concomitant functioning of the other aminoacyl-tRNA synthetases. The sedimentation behavior of the aminoacyl-tRNA synthetase components of the complex under conditions prevailing in the tRNA aminoacylation assay indicates that they remain associated under these conditions. The implications of these findings on the structural organization of the enzymes within the complex are discussed.