Izumo sperm-oocyte fusion protein 1 (IZUMO1)

IZUMO1 is a sperm-specific, immunoglobulin-like type I transmembrane protein essential for the recognition and adhesion of sperm to oocytes (egg cells) during mammalian fertilization[1][2][3][4]. It localizes to the sperm’s acrosomal membrane and, post-acrosome reaction, to the equatorial segment of the sperm, where it interacts with its receptor JUNO (also known as FOLR4) on the egg surface[3][5]. Crystal structures reveal a boomerang-shaped architecture, featuring a four-helix bundle (the Izumo domain) and a glycosylated Ig-like domain, stabilized by conserved disulfide bonds[1][4]. Binding of IZUMO1 to JUNO is necessary for sperm-egg membrane fusion, and knockouts of either protein in mice lead to infertility without other health effects[3][5]. IZUMO1 does not act as a classical viral fusogen but may function as a scaffold or adhesion protein that facilitates multiprotein fusion complexes, triggering membrane apposition and eventual fusion[1][4]. The high-affinity interaction between IZUMO1 and JUNO provides a promising research platform for designing non-hormonal contraceptives, though no drugs or diagnostic biomarkers are in clinical use as of the latest scientific reports[3][4][5].

Other names

Izumo sperm-egg fusion protein 1Oocyte binding/fusion factorOBFSperm-specific protein IzumoMGC34799IZUMOizumo sperm-oocyte fusion 1oocyte binding/fusion factorizumo sperm-egg fusion 1sperm-specific protein Izumo