first tandem Wiskott-Aldrich Syndrome Homology (WASP) region 2 (WH2 motif) repeat found in Drosophila melanogaster Spire, and similar proteins
This family contains the first of four tandem repeats of Wiskott-Aldrich syndrome protein (WASP)-homology domain 2 (WH2) in Drosophila melanogaster Spire (also called Spir), an actin nucleator essential for establishing an actin mesh during oogenesis. Spire was first identified as a Drosophila maternal effect gene essential to establishment of both the anterior/posterior and dorsal/ventral body axes in developing oocytes and embryos. It has been found to sever filaments and sequester monomers in addition to nucleating new filaments; it remains associated with the slow-growing pointed end of the new filament. Spire promotes dissociation of the actin nucleator Cappuccino (Capu) from the barbed end of actin filaments. Spire is involved in intracellular vesicle transport along actin fibers, providing a link between actin cytoskeleton dynamics and intracellular transport. Drosophila Spire contains four tandem WH2 domains which appear to function by determining the size of filament nuclei according to the number of WH2 repeats, suggesting that the WH2 domains of Spire line up actin subunits along a filament strand of the actin double helix, thereby generating nuclei for actin assembly. This model contains the first tandem WH2 domain of Spire (also called Spir-A or WH2-A).
Jiyao W et al.(2023). "The conserved domain database in 2023.",