Fig. 7. Binding of LKB1 to STRADα creates novel binding site(s) for MO25α. The indicated forms of GST–STRADα were co-expressed in 293 cells together with Myc-MO25α and/or wild-type Flag-LKB1 or the isolated LKB1 catalytic domain (LKB1[44–343]). Thirty-six hours post-transfection, the GST–STRADα proteins were affinity purified, subjected to SDS–PAGE and immunoblotting with anti-Myc antibody to detect Myc-MO25α, anti-Flag antibody to detect co-purified Flag-LKB1 and Flag-LKB1[44–343], or with anti-GST antibody to detect STRADα forms (upper panels). Five micrograms of total cell lysates prior to affinity purification were also subjected to immunoblotting with anti-Myc and anti-Flag antibodies to ensure that MO25α and LKB1 were expressed at similar levels in each co-transfection (lower panels). Similar results were obtained in three separate experiments.