Cerini C, Kerjan P, Astier M, Gratecos D, Mirande M, Sémériva M
Laboratoire de Génétique et Biologie Cellulaires, CNRS, Marseille, France.
EMBO J. 1991 Dec;10(13):4267-77. doi: 10.1002/j.1460-2075.1991.tb05005.x.
In higher eukaryotes, nine aminoacyl-tRNA synthetases are associated within a multienzyme complex which is composed of 11 polypeptides with molecular masses ranging from 18 to 150 kDa. We have cloned and sequenced a cDNA from Drosophila encoding the largest polypeptide of this complex. We demonstrate here that the corresponding protein is a multifunctional aminoacyl-tRNA synthetase. It is composed of three major domains, two of them specifying distinct synthetase activities. The amino and carboxy-terminal domains were expressed separately in Escherichia coli, and were found to catalyse the aminoacylation of glutamic acid and proline tRNA species, respectively. The central domain is made of six 46 amino acid repeats. In prokaryotes, these two aminoacyl-tRNA synthetases are encoded by distinct genes. The emergence of a multifunctional synthetase by a gene fusion event seems to be a specific, but general attribute of all higher eukaryotic cells. This type of structural organization, in relation to the occurrence of multisynthetase complexes, could be a mechanism to integrate several catalytic domains within the same particle. The involvement of the internal repeats in mediating complex assembly is discussed.
在高等真核生物中，9种氨酰-tRNA合成酶与一个多酶复合体相关联，该复合体由11种分子量在18至150 kDa之间的多肽组成。我们从果蝇中克隆并测序了一个编码该复合体最大多肽的cDNA。我们在此证明相应的蛋白质是一种多功能氨酰-tRNA合成酶。它由三个主要结构域组成，其中两个结构域具有不同的合成酶活性。氨基末端和羧基末端结构域分别在大肠杆菌中表达，并分别被发现可催化谷氨酸和脯氨酸tRNA种类的氨酰化。中央结构域由六个46个氨基酸的重复序列组成。在原核生物中，这两种氨酰-tRNA合成酶由不同的基因编码。通过基因融合事件产生多功能合成酶似乎是所有高等真核细胞的一个特定但普遍的特征。这种结构组织类型，与多合成酶复合体的出现相关，可能是一种将多个催化结构域整合到同一颗粒中的机制。本文还讨论了内部重复序列在介导复合体组装中的作用。
