A region of mLin-2/CASK encompassing the GK domain binds to X11α. A, C, Myc-tagged X11α protein expressed in 293 cells was precipitated with different mLin-2/CASK GST fusion proteins and revealed with anti-myc antibody after Western blot. We have also detected binding to nonmyc-tagged constructs (results not shown). B, Brain, liver, and kidney extracts were run on a gel, and proteins were transferred to nitrocellulose. Myc-tagged X11α protein expressed in 293 cells was used as a positive control (X11α). An overlay assay was performed with soluble GST fusion proteins. Bound GST proteins were revealed using anti-GST antibody–HRP protein A chemiluminescence method.