The p43 Component of the Mammalian Multi-synthetase Complex Is Likely To Be the Precursor of the Endothelial Monocyte-activating Polypeptide II Cytokine

Sophie Quevillon,Fabrice Agou,Jean-Charles Robinson,Marc Mirande

doi:10.1074/jbc.272.51.32573

Abstract

p43 is one of the three auxiliary components invariably associated with nine aminoacyl-tRNA synthetases as a multienzyme complex ubiquitous to all eukaryotic cells from flies to humans. The cDNA encoding the hamster protein was isolated by using mixed oligonucleotides deduced from peptide sequences. The 359-amino acid protein is the hamster homologue of the recently reported murine and human EMAP II cytokine implicated in a variety of inflammatory disorders. The sequence of several proEMAP II proteins suggests that the p43 component of the complex is the precursor of the active mature cytokine after cleavage at a conserved Asp residue. The COOH-terminal moiety of p43 is also homologous to polypeptide domains found in bacterial methionyl- or phenylalanyl-tRNA synthetases and in the yeast Arc1p/G4p1 protein that associates with yeast methionyl-tRNA synthetase. Our results implicate the COOH-terminal moiety of p43 as a RNA binding domain. In the native state, as a component of the multisynthetase complex, p43 may be required for tRNA channeling and, after proteolytic processing occurring in tumor cells, would acquire inflammatory properties possibly related to apoptosis. The release of a truncated p43 from the complex could be involved in mediation of the signaling of tumor cells and stimulation of an acute inflammatory response.

Highlights

The nucleotide sequence(s) reported in this paper has been submitted to the GenBankTM/EBI Data Bank with accession number(s) AF021800
Structural Behavior of Human p43—Because two distinct protein species related to p43, a component of the multisynthetase complex and a precursor of the endothelial monocyteactivating polypeptides (EMAP) II cytokine, have been described, we considered the possibility that two discrete polypeptides expressed from the same gene coexist within the cell
The NH2-terminal moiety of the protein of about 200 amino acid residues displays no significant homology with proteins of known function registered in the data libraries

Summary

EXPERIMENTAL PROCEDURES

General Recombinant DNA Techniques—All recombinant manipulations were carried out using standard procedures [16]. Fractions containing p43Ct (eluted at 165 mM) were pooled (36 ml), concentrated, dialyzed against 20 mM potassium phosphate, pH 7.5, 1 mM dithioerythritol, and stored at Ϫ70 °C at a protein concentration of 11 mg/ml. Analytical Gel Filtration—The apparent native molecular mass of p43Ct was determined by gel filtration on a Superose 12 HR 10/30 (Pharmacia) column equilibrated in 50 mM potassium phosphate, pH 7.5, 10 mM ␤-mercaptoethanol containing 10% of glycerol where indicated and developed at room temperature at a flow rate of 0.4 ml1⁄7minϪ1. Homogeneous human p43Ct (1.6 pmol to 5 nmol) was incubated with in vitro transcribed tRNA (10 fmol, 107 cpm/pmol) in the binding buffer containing 20 mM Tris-HCl, pH 7.5, 150 mM NaCl, 10 mM MgCl2, 10 mM 2-mercaptoethanol, and 10% glycerol in a final volume of 10 ␮l. When homopolymeric ribonucleotides were used, they were end-labeled with [␥-32P]ATP and T4 polynucleotide kinase

RESULTS

AAR ATH TGG GAR CA

DISCUSSION