Structure of protein PH0536 from Pyrococcus horikoshii at 1.7 A resolution reveals a novel assembly of an oligonucleotide/oligosaccharide-binding fold and an alpha-helical bundle.

摘要

Aminoacyl-tRNA synthetases (ARSs) catalyze the cova-lent linking of amino acids and their cognate tRNAs to decode genetic information. ARSs are at the center of the question of the origin of life. Their evolution is of particular importance for understanding the evolution of translation and the transition from the RNA world to modern DNA-based forms of life. A plausible scheme for the evolution of these proteins has been proposed in which the class-defining domain is likely to be the oldest module with later inclusion of additional domains in extant ARSs. At any stage of this evolutionary process, single domains or combinations of these domains have diverged to generate extant aminoacyl-tRNA synthetase-like proteins. For this reason, the structures of aminoacyl-tRNA synthetase-like proteins (or domains) are of great interest. EMAP IP (endotheiial monocyte activating polypeptide II) and Trbplll" (an ancient structure-specific tRNA-binding protein) are two examples of amino-acyl-tRNA synthetase-like proteins. EMAP II (functional cytokine domain), the C-terminal 166 residues of its precursor (pro-EMAP II), is an anti-tumor cytokine and it can also interact with different tRNAs. It has been reported that the full-length pro-EMAP II is involved in the formation of a multi-ARS complex containing at least nine different ARSs.