Cysteine-rich domain of the smoothened receptor (Smo) integral membrane protein.
The cysteine-rich domain (CRD) is part of the smoothened receptor (Smo), an integral membrane protein and one of the key players in the Hedgehog (Hh) signaling pathway, critical for development, cell growth and migration, as well as stem cell maintenance. The CRD of Smo is conserved in vertebrates and can also be identified in invertebrates. The precise function of the CRD in Smo is unknown. Mutations in the Drosophila CRD disrupt Smo activity in vivo, while deletion of the CRD in mammalian cells does not seem to affect the activity of overexpressed Smo.