The list is long and varied. Acting counter to this activation is Yan , a negative regulator of R7 fate. The Sevenless signaling which initiates R7 photoreceptor maturation, triggers a phosphorylation cascade that activates transcription factors, modifies cell cycle regulation, affects basal transcription factors and involves protein chaperones. Even the Notch pathway is brought into play to restrict the effects of a ligand-receptor interaction. The transmembrane domain stretches from residues 2042-2051.
Sevenless protein possesses protein tyrosine kinase activity.
The protein is first synthesized as a 280-kDa glycoprotein precursor. The DNA sequence of the sevenless gene from Drosophila melanogaster has been compared with that of D. virilis . The two species diverged approximately 60 million years ago.