(A) Phosphorylation of TTP in intact HEK-293 cells. Lanes 1, 2, 3 and 4 represent [32P]orthophosphate-labelled proteins eluted with 100, 200, and 250 mM imidazole buffer and the residual protein bound to the Ni-NTA beads respectively. (B, C) Purification of TTP for MS analysis. TTP was purified with Ni-NTA beads from transfected HEK-293 cells, separated by SDS/PAGE and detected by silver staining (B) or by immunoblotting with the anti-MBP-hTTP antibodies (C).