Interactions Between Wingless and Frizzled Molecules in Drosophila 5
CRD
Fig. 2. Structure of Frizzled proteins
acts onjz. most studies have not revealed any role for wg in PP, suggesting another ligand, possibly another Drosophila Wnt.
Fz proteins are part of the large family of seven membrane-spanning
domain receptors (Fig. 2). In Drosophila, this gene family counts several members, including Dfz2 (Bhanot et al. 1996). The Smoothened
protein (Smo), known by genetic analysis to be a component of Hedgehog signaling, is also homologous to the Fz family, yet is the most
divergent family member at the sequence level (Alcedo et al. 1996; Van
Den Heuvel and Ingham 1996) .
. Fz proteins contain several structural similarities: a conserved extracellular region containing ten invariant cysteines (CRD); seven hydrophobic segments; and a C-terminus containing a valine residue in a
somewhat conserved threonine/serine-X-valine motif (T/SXV), a putative binding site for the PDZ domain (Gomperts 1996; Wang et al.
1996).
Little is known about signaling mechanisms by these receptors. Although the Fz proteins show no primary sequence homology to other
known proteins, the structural motifs are reminiscent of G-protein coupled seven-transmembrane segment receptors, with extracellular N-terminal ligand-binding domains, and cytosolic C-termini (Wang et al.
1996). These results suggest a similar structure for Fz proteins and
G-protein coupled receptors, although with many G-protein coupled
receptors, residues in the transmembrane domains or extracellular loops
CRD
Fig. 2. Structure of Frizzled proteins
acts onjz. most studies have not revealed any role for wg in PP, suggesting another ligand, possibly another Drosophila Wnt.
Fz proteins are part of the large family of seven membrane-spanning
domain receptors (Fig. 2). In Drosophila, this gene family counts several members, including Dfz2 (Bhanot et al. 1996). The Smoothened
protein (Smo), known by genetic analysis to be a component of Hedgehog signaling, is also homologous to the Fz family, yet is the most
divergent family member at the sequence level (Alcedo et al. 1996; Van
Den Heuvel and Ingham 1996) .
. Fz proteins contain several structural similarities: a conserved extracellular region containing ten invariant cysteines (CRD); seven hydrophobic segments; and a C-terminus containing a valine residue in a
somewhat conserved threonine/serine-X-valine motif (T/SXV), a putative binding site for the PDZ domain (Gomperts 1996; Wang et al.
1996).
Little is known about signaling mechanisms by these receptors. Although the Fz proteins show no primary sequence homology to other
known proteins, the structural motifs are reminiscent of G-protein coupled seven-transmembrane segment receptors, with extracellular N-terminal ligand-binding domains, and cytosolic C-termini (Wang et al.
1996). These results suggest a similar structure for Fz proteins and
G-protein coupled receptors, although with many G-protein coupled
receptors, residues in the transmembrane domains or extracellular loops