Cytoplasmic aminoacyl-tRNA synthetases of higher eukaryotes acquired extra peptides in the course of their evolution. It has been thought that these appendices are related to the occurrence of the multiprotein complex consisting of at least eight different tRNA synthetase polypeptides. This complex is believed to be a signature feature of metazoans. In this study, we used multiple sequence alignments to infer the locations of the peptide appendices from human cytoplasmic tRNA synthetases found in the multisynthetase complex. The selected peptide appendices ranged from 22 aa of aspartyl-tRNA synthetase to 267 aa of methionyltRNA synthetase. We then made genetic constructions to investigate interactions between all 64 combinations of these peptides that were individually fused to nonsynthetase test proteins. The analyses identified 11 (10 heterologous and 1 homologous) interactions. The six peptide-dependent interactions paralleled what had been detected by crosslinking methods applied to the isolated multisynthetase complex. Thus, small peptide appendices seem to link together different synthetases into a complex. In addition, five interacting pairs that had not been detected previously were suggested from the observed peptide-dependent complexes.

Endothelial monocyte activating polypeptide II (EMA-PII) 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 Nterminal 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 K m of RRS to tRNA, whereas the k cat 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.Aminoacyl-tRNA synthetases (ARSs) 1 catalyze ligation of their cognate amino acids to specific tRNAs. Although basic architecture of the core domain is well conserved among ARSs, unique peptide extensions have been found in the N-or Cterminal ends of metazoan enzymes (1-3). Although these extensions have been thought to be involved in heterologous molecular interactions, their functional significance is not yet understood.A macromolecular protein complex consisting of at least nine different ARSs has been found in higher eukaryotes (1-3). This multi-ARS complex also contains three nonsynthetase components, p18, p38, and p43 whose functions are not clear (4 -7). Among these nonsynthetase components, p43 has been proposed to be a precursor of a tumor-specific cytokine, endothelial monocyte-activating polypeptide II (EMAPII) based on over 80% sequence identity between the two proteins (6). EMAPII was originally identified in the culture medium of murine fibrosarcoma cells induced by methylcholanthrene A (8). It triggers an acute inflammatory response (9, 10) and is involved in development-related apoptosis (11).The precursor for EMAPII (pro-EMAPII) is processed at the Asp residue of ASTD/S sequence to release the C-terminal cytokine domain of 23 kDa (11). Its C-terminal domain shares homology with the C-terminal parts of methionyl-tRNA synthetases of prokaryotes, archaea and nematode, and also a yeast protein, Arc1p/G4p, which interacts with methionyl-and glutamyl-tRNA synthetases. The N-terminal domain of pro-EMAPII does not show homology to any known proteins, and its function has not been understood.EMAPII is expressed in a wide range of cell lines and normal tissues (12) and its mRNA level is unchanged during apoptosis (11) although its production is induced by apoptosis. The present work was designed to address whether pro-EMAPII is identical to p43 and to understand its function in the normal cell. The results showed that pro-EMAPII is associated with the N-terminal extension of human arginyl-tRNA synthetase (RRS), facilitating aminoacylation reaction. EXPE...

Tandem repeats located in the human bifunctional glutamyl-prolyl-tRNA synthetase (EPRS) have been found in many different eukaryotic tRNA synthetases and were previously shown to interact with another distinct repeated motifs in human isoleucyl-tRNA synthetase. Nuclear magnetic resonance and differential scanning calorimetry analyses of an isolated EPRS repeat showed that it consists of a helix-turn-helix with a melting temperature of 59°C. Specific interaction of the EPRS repeats with those of isoleucyl-tRNA synthetase was confirmed by in vitro binding assays and shown to have a dissociation constant of approximately 2.9 M. The EPRS repeats also showed the binding activity to the N-terminal motif of arginyl-tRNA synthetase as well as to various nucleic acids, including tRNA. Results of the present work suggest that the region comprising the repeated motifs of EPRS provides potential sites for interactions with various biological molecules and thus plays diverse roles in the cell.

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The study aim s to explore the problem s of analysis unit w hen exam ining m anagem ent perform ance and efficiency using DEA (Data Envelopm ent Analysis). Generally the DEA results depend on input, output, and analysis units. W e used data from Park (2012) which analyze paddy farm ers in Jeonnam province. Results show that data from farm household unit w as w ell fitted to exam ine m anagem ent efficiency, not data from per area unit. This study w ill be helpful for researchers and practitioners to understand proper analysis unit w hen using the DEA for enhancing farm com petitiveness.