Fig. 1. Sra-1 binds Kette through its C terminus. (A) Whole-mount stage 16 embryos stained for kette or sra-1 RNA expression as indicated, (Left) Lateral views; (middle) ventral views; (right) higher magnifications of the ventral nerve cord showing ubiquitous expression of both genes. (B) Western blot analyses of Kette (120 kDa) and Sra-1 (140 kDa) expression. Both proteins are expressed throughout embryogenesis and appear to be provided maternally. (C) Co-immunoprecipitation of Kette and Sra-1. Total cell lysate of S2-cells expressing both Myc-tagged Kette and Sra-1 was subjected to immunoprecipitation with monoclonal anti-Myc (9E10) or anti-Slit (E555.6D). Sra-1 is detected only in the anti-Myc precipitate, indicating binding of Kette and Sra-1. (D) To test the interaction between Sra-1 and Kette, we turned to a yeast two hybrid assay. Interaction between Sra-1 and Kette results in growth of the yeast cells and a blue color. Interaction is seen only when the C terminus is intact (E).