The Hedgehog (Hh) signaling pathway is a highly conserved regulator of growth and differentiation that is essential for both vertebrate and invertebrate development. In Drosophila, the HH pathway is regulated by a high molecular weight intracellular protein complex called the Hedgehog Transducing Complex (HTC), whose composition is controlled by the activation of the pathway. My thesis project is to characterise the HTC complex that regulates the fate of the HH transcription factor, CI. I am using structural studies, biochemistry and enzymology to better understand the protein-protein interactions and function that govern the Hedgehog pathway. My work provide a high resolution view of the HTC and help to understand how those proteins work and interact with each other.