FGF domain, beta-trefoil fold, found in Drosophila melanogaster protein branchless (Bnl) and similar proteins
Protein Bnl is a homolog of mammalian fibroblast growth factors. It is a dosage-sensitive regulator of terminal branching. It functions as a chemoattractant that can guide terminal branches to new tissues and even to individual cells within a tissue. Bnl contains a FGF domain with beta-trefoil fold, which is characterized by 12 beta strands folded into three similar trefoil subdomains (alpha, beta, and gamma) associated to give an overall structure with pseudo-3-fold symmetry.
Jiyao W et al.(2023). "The conserved domain database in 2023.",