A MULTIFUNCTIONAL REPEATED MOTIF IS PRESENT IN HUMAN BIFUNCTIONAL TRANSFER-RNA SYNTHETASE

Tandem repeats located in the human bifunctional glutamyl-prolyl-tRNA synthetase (EPRS) have been found in many different eukaryotic tRNA sy nthetases and were previously shown to interact with another distinct repeated motifs in human isoleucyl-tRNA synthetase. Nuclear magnetic r esonance and differential scanning calorimetry analyses of an isolated ERRS repeat showed that it consists of a helix-turn-helix with a melt ing temperature of 59 degrees C. Specific interaction of the EPRS repe ats with those of isoleucyl-tRNA synthetase was confirmed by in vitro binding assays and shown to have a dissociation constant of approximat ely 2.9 mu M. The EPRS repeats also showed the binding activity to the N-terminal motif of arginyl-tRNA synthetase as well as to various nuc leic acids, including tRNA. Results of the present work suggest that t he region comprising the repeated motifs of ERRS provides potential si tes for interactions with various biological molecules and thus plays diverse roles in the cell.