The A-box of Elk-1 is necessary for interaction with p35-C/EBPβ in vitro. A) Schematic representation of Elk-1 wild-type and deletion mutants. B) Radiolabeled Elk-1(wt), Elk-1(1-209), Elk-1(1-140), and Elk-1(89-428) were prepared by in vitro transcription and translation of their respective expression constructs (see Mat. and Meth.). The proteins were incubated with equivalent amounts of GST or GST-p35-C/EBPβ protein immobilized on glutathione-Sepharose. Proteins eluted from the GST beads (lanes 2) or GST-p35-C/EBPβ beads (lanes 3) were resolved on an SDS-10% polyacrylamide gel and detected by autoradiography. Lane 1 contains one-half of the amount of the radiolabeled proteins initially mixed with the beads.