Structure of phenylalanyl-tRNA synthetase from Thermus Thermophilus

The crystal structure of phenylalanyl-tRNA synthetase from Thermus thermophilus, solved at 2.9 Å resolution, displays (αβ)₂ subunit organization. Unexpectedly, both the catalytic α- and the non-catalytic β-subunits comprise the characteristic fold of the class II active-site domains. The αβ heterodimer contains most of the building blocks so far identified in the class II synthetases. The presence of an RNA-binding domain, similiar to that of the U1A spliceosomal protein, in the β-subunit is indicative of structural relationships among different families of RNA-binding proteins. The structure suggests a plausible catalytic mechanism which explains why the primary site of tRNA aminoacylation is different from that of the other class II enzymes.