Recombinant wt and mutant GST-CLP1 was purified from E. coli and tested for kinase activity as previously described (Ramirez et al., 2008). Double affinity purification of FlagHis-CLP1 was carried out as previously described (Trotta et al., 2006; Volta et al., 2005). Associated protein complexes were used in tRNA endonuclease assays and analyzed by Western blot. Detailed experimental techniques can be found in the Extended Experimental Procedures.
