STRUCTURE OF PHENYLALANYL-TRANSFER-RNA SYNTHETASE FROM THERMUS-THERMOPHILUS

The crystal structure of phenylalanyl-tRNA synthetase from Thermus the rmophilus, solved at 2.9 Angstrom resolution, displays (alpha beta)(2) subunit organization, Unexpectedly, both the catalytic alpha- and the non-catalytic beta-subunits comprise the characteristic fold of the c lass II active-site domains, The alpha beta 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 spl iceosomal protein, in the beta-subunit is indicative of structural rel ationships among different families of RNA-binding proteins, The struc ture suggests a plausible catalytic mechanism which explains why the p rimary site of tRNA aminoacylation is different from that of the other class II enzymes.