Hedgehog Homolog, Sonic (SHH)

Sonic hedgehog (Shh) is a member of a small family of secreted proteins that are essential for development in both vertebrates and invertebrates. In mammals, there are three related hedgehog genes (sonic; desert; Indian) which share approximately 60 % amino acid (aa) identity. Human Shh is synthesized as a 437 aa precursor that contains a 24 aa signal sequence and a 413 aa mature region.

The mature region is autocatalytically processed into a nonglycosylated, 20 kDa, 174 aa N-terminal fragment (Shh-N), and a catalytic-processing, glycosylated, 34 kDa, 239 aa C-terminal fragment.The 20 kDa Shh-N fragment is the core of the active hedgehog molecule. It begins with a Cys and ends with a Gly, and both amino acids are sites of lipid modification.