Expression, purification, crystallization and preliminary phasing of the heteromerization domain of the tRNA-export and aminoacylation cofactor Arc1p from yeast.

Eukaryotic aminoacyl-tRNA synthetases (aaRSs) must be integrated into an efficient tRNA-export and shuttling machinery. This is reflected by the presence of additional protein-protein interaction domains and a correspondingly higher degree of complex formation in eukaryotic aaRSs. However, the structural basis of interaction between eukaryotic aaRSs and associated protein cofactors has remained elusive. The N-terminal heteromerization domain of the tRNA aminoacylation and export cofactor Arc1p has been cloned from yeast, expressed and purified. Crystals have been obtained belonging to space group C2, with unit-cell parameters a = 222.32, b = 89.46, c = 126.79 angstroms, beta = 99.39 degrees. Calculated Matthews coefficients are compatible with the presence of 10-25 monomers in the asymmetric unit. A complete multiple-wavelength anomalous dispersion data set has been collected from a selenomethionine-substituted crystal at 2.8 angstroms resolution. Preliminary phasing reveals the presence of 20 monomers organized in five tetramers per asymmetric unit.