Fig. 1. ERKs phosphorylate IEX-1 in vitro. (A) One microgram of purified GST or GST–IEX-1 fusion proteins wild-type (Wt) and mutants (T18A; T123AS126A; T/SA3; ΔBD) were reacted with purified recombinant active ERK2 in the presence of [³²P]ATP. The products were analyzed by autoradiography or western blotting (WB) with the indicated antibodies. (B) Schematic representation of IEX-1 Wt and ERK-phosphorylation and/or binding sites mutants. Hatched area indicates the putative IEX-1 transmembrane domain.