Precursor of pro-apoptotic cytokine modulates aminoacylation activity of tRNA synthetase.
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.[1]References
- Precursor of pro-apoptotic cytokine modulates aminoacylation activity of tRNA synthetase. Park, S.G., Jung, K.H., Lee, J.S., Jo, Y.J., Motegi, H., Kim, S., Shiba, K. J. Biol. Chem. (1999) [Pubmed]
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