Figure 6.

The transmembrane domains of Ptch1 and Ptch2 are equivalent functional modules. A, stick diagram illustrating the specific amino acid boundaries of the Ptch1–Ptch2 constructs used in this assay. Included below are the DNA and amino acid sequences for the boundaries of the chimeric proteins. B, Ptch1-deficient MEFs were transiently transfected with an 8×Gli-luciferase construct, a constitutively expressing Renilla luciferase construct, and constructs expressing Ptch1–Ptch2 chimeras. Cells were serum-starved for 48 h and treated with either control (pcDNA3) or N-Shh conditioned medium for 24 h. Ptch1 chimeras with either or both SSDs from Ptch2 fully repressed Smo and responded to Hh ligand, demonstrating that the SSDs in Ptch1 and Ptch2 are functionally equivalent despite the lack of repression activity of the intact Ptch2 protein. **, p < 0.01; ***, p < 0.001.