Fig. 5. Perd protein physically interacts with Grip and localizes it to muscle attachment sites. (A,B) Individual PDZ domains from Grip were prepared as GST fusion proteins, incubated with epitope-tagged Perd intracellular domain, and purified by glutathione affinity (PDZ2 was not successfully assessed in this experiment). Detection of the epitope tag (A) shows that PerdIC is present only when Grip PDZ7 is present, whereas anti-GST antibody (B) reveals that fusion protein was present in all lanes. (C-H) Double-labeling of wild-type embryos for myosin heavy chain and Grip protein shows that Grip is localized to sites of muscle attachment. In perd mutant embryos (I-N), Grip protein fails to localize and is visible over the entire periphery of Grip-expressing muscles. F-H and l-N are higher magnification images of part of the embryos shown in C-E and I-K, respectively.