Park S G, Jung K H, Lee J S, Jo Y J, Motegi H, Kim S, Shiba K
National Creative Research Initiatives Center for ARS Network, Sung Kyun Kwan University, Suwon, Kyunggido, 440-746, Korea.
J Biol Chem. 1999 Jun 11;274(24):16673-6. doi: 10.1074/jbc.274.24.16673.
Endothelial monocyte activating polypeptide II (EMAPII) is a cytokine that is specifically induced by apoptosis. Its precursor (pro-EMAPII) has been suggested to be identical to p43, which is associated with the multi-tRNA synthetase complex. Herein, we have demonstrated that the N-terminal domain of pro-EMAPII interacts with the N-terminal extension of human cytoplasmic arginyl-tRNA synthetase (RRS) using genetic and immunoprecipitation analyses. Aminoacylation activity of RRS was enhanced about 2.5-fold by the interaction with pro-EMAPII but not with its N- or C-terminal domains alone. The N-terminal extension of RRS was not required for enzyme activity but did mediate activity stimulation by pro-EMAPII. Pro-EMAPII reduced the apparent Km of RRS to tRNA, whereas the kcat value remained unchanged. Therefore, the precursor of EMAPII is a multi-functional protein that assists aminoacylation in normal cells and releases the functional cytokine upon apoptosis.
内皮单核细胞激活多肽II（EMAPII）是一种由细胞凋亡特异性诱导产生的细胞因子。其前体（前EMAPII）被认为与p43相同，p43与多tRNA合成酶复合体相关。在此，我们通过遗传学和免疫沉淀分析证明，前EMAPII的N端结构域与人细胞质精氨酰-tRNA合成酶（RRS）的N端延伸相互作用。RRS的氨酰化活性通过与前EMAPII相互作用而增强约2.5倍，但单独与前EMAPII的N端或C端结构域相互作用则无此效果。RRS的N端延伸对于酶活性不是必需的，但确实介导了前EMAPII对活性的刺激作用。前EMAPII降低了RRS对tRNA的表观Km值，而kcat值保持不变。因此，EMAPII的前体是一种多功能蛋白，在正常细胞中协助氨酰化，并在细胞凋亡时释放功能性细胞因子。
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