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FYVE-related domain found in Spir proteins, Spire1 and Spire2 Spir proteins were originally discovered as the protein products of the Drosophila spire gene. They are Jun N-terminal kinase (JNK)-interacting proteins that have exclusively been identified in metazoans. They may play roles in membrane trafficking and cortical filament crosslinking. This family includes Spire1 and Spire2, which function as new essential factors in asymmetric division of oocytes. They mediate asymmetric spindle positioning by assembling a cytoplasmic actin network. They are also required for polar body extrusion by promoting assembly of the cleavage furrow. Moreover, they cooperate synergistically with Fmn2 to assemble F-actin in oocytes. Both Spire1 and Spire2 contain an N-terminal protein-interaction KIND domain, WH2 actin-binding domains, a Rab GTPase-interaction Spir-box, and a C-terminal FYVE membrane-binding domain. Their FYVE domains resemble FYVE-related domains that are structurally similar to the canonical FYVE domains but lack the three signature sequences: an N-terminal WxxD motif (x for any residue), the central basic R(R/K)HHCRxCG patch, and a C-terminal RVC motif, which form a binding pocket that specifically bind the phospholipid phosphatidylinositol 3-phosphate (PtdIns3P or PI3P). |
Jiyao W et al.(2023). "The conserved domain database in 2023.",