Figure 4.

 Binding of Dorsal to Gro. (A) GST fusion proteins purified and immobilized on glutathione agarose beads were incubated with in vitro translated, ³⁵S-labeled proteins. After extensive washing, bound proteins were eluted from the beads and analyzed by SDS-PAGE and autoradiography. (Lanes 1–4) 1/10th the amount of input ³⁵S-labeled proteins used in the binding assay; (lanes 5–14) the ³⁵S-labeled proteins after binding to the indicated immobilized GST fusions proteins. The ³⁵S-labeled proteins are luciferase (lanes 1,8,10), Dorsal (lanes 2,5,11,13), Dorsal 379 (lanes 3,6,12), and Gro (lanes 4,7,9,14). (B) Coimmunoprecipitation experiments: Sf9 cells were infected with an empty baculovirus expression vector (lanes 1,2), a vector expressing Dorsal (lanes 3,4), a vector expressing M2-tagged Gro (lanes 5,6), or vectors expressing Dorsal and M2-tagged Gro (lanes 7,8). (Lanes 1,3,5,7) crude nuclear extracts of infected cells; (lanes 2,4,6,8) immunoprecipitates obtained using the anti-M2 antibody. Immunoblots were probed with anti-M2 (top) or anti-Dorsal (bottom) antibodies.