This entry represents Izumo sperm-egg fusion protein 2 (IZUMO2), a member of the IZUMO family.IZUMO is a protein with asingle immunoglobulin (Ig) domain. Its expression has been found to be testis-specific [, ]. IZUMO is not detectable on the surface of fresh sperm, but becomes exposed after an exocytotic process, the acrosome reaction, has occurred. It is thought to bind to putative Izumo receptors on the oocyte. Studies have shown that knock-out mice (Izumo-/- males) were sterile despite normal mating behaviour and ejaculation, indicating the importance of the protein in fertilisation []. IZUMO is a typical type I membrane glycoprotein with one immunoglobulin-like domain and a putative N-glycoside link motif (Asn 204) []. It contains cysteine residues thought to form a disulphide bridge, and a conserved GCL sequence motif.
