A recurrent RNA-binding domain is appended to eukaryotic aminoacyl-tRNA synthetases

Aminoacyl-tRNA synthetases of higher eukaryotes possess polypeptide extensi ons in contrast to their prokaryotic counterparts. These extra domains of p oorly understood function are believed to be involved in protein-protein or protein-RNA interactions. Here we showed by gel retardation and filter bin ding experiments that the repeated units that build the linker region of th e bifunctional glutamyl-prolyl-tRNA synthetase had a general RNA-binding ca pacity. The solution structure of one of these repeated motifs was also sol ved by NMR spectroscopy. One repeat is built around an antiparallel coiled- coil, Strikingly, the conserved lysine and arginine residues form a basic p atch on one side of the structure, presenting a suitable docking surface fo r nucleic acids. Therefore, this repeated motif may represent a novel type of general RNA-binding domain appended to eukaryotic aminoacyl-tRNA synthet ases to serve as a cis-acting tRNA-binding cofactor.