Sonic hedgehog is an important signalling molecule for developmental patterning. There are several vertebrate genes that resemble the hedgehog gene first defined in Drosophila: Sonic hedgehog, Indian hedgehog, and Desert hedgehog. Sonic hedgehog has been identified as a key factor in the determination of the ventral neural tube, the anterior/posterior axis of the limb, and and cartilage-producing region of the somites.
The developmentally active part of the Sonic hedgehog precursor is the amino half of the molecule, which is the sequence represented below. This half of the molecule is removed by the enzymatic activity of the carboxyl half of the molecule.
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* * = leader sequence
( ) = alpha helix
[ ] = beta sheet
< > = turn
Notes on the music.
This piece is a single read-through of the sequence of the developmentally active amino half of the molecule. The 23-amino acid signal sequence is heard first, played by low strings. The active amino half of the precursor then enters, played by oboe. The DNA sequence enters briefly, played as triplets under the protein theme. The oboe continues to play the more water-soluble amino acids of the protein, along with clarinet playing the less water-soluble amino acids. A solo viola plays the alpha helix sections of the protein, tubular bells play the turns, and pizzicato viola plays the beta strands.