Izumo Sperm Egg Fusion 1 (IZUMO1)

The sperm-specific protein Izumo, named for a Japanese shrine dedicated to marriage, is essential for sperm-egg plasma membrane binding and fusion.Mass spectrometry, RT-PCR analysis of testis RNA, and database searching elucidated the DNA sequence and identified a human homolog . The predicted human gene encodes a 350-amino acid type I membrane protein of the Ig superfamily containing an extracellular Ig domain with a putative glycosylation site. Western blot analysis detected a 37-kD protein on the sperm surface after the exocytotic acrosome reaction process but not on fresh sperm. Anti-IZUMO, but not control, polyclonal antibody treatment inhibited fusion with zona pellucida-free hamster eggs.