Structural highlights
Function
[IZUM1_MOUSE] Essential sperm cell-surface protein required for fertilization by acting as a ligand for IZUMO1R/JUNO receptor on egg. The IZUMO1:IZUMO1R/JUNO interaction is a necessary adhesion event between sperm and egg that is required for fertilization but is not sufficient for cell fusion. The ligand-receptor interaction probably does not act as a membrane 'fusogen'.[1] [2]
Publication Abstract from PubMed
Fertilization, the culminating event in sexual reproduction, occurs when haploid sperm and egg recognize each other and fuse to form a diploid zygote. In mammals this process critically depends on the interaction between Izumo1, a protein exposed on the equatorial segment of acrosome-reacted sperm, and the egg plasma-membrane-anchored receptor Juno [1,2]. The molecular mechanism triggering gamete fusion is unresolved because both Izumo1 and Juno lack sequence similarity to known membrane fusogens. Here we report the crystal structure of Izumo1, which reveals a membrane distal region composed of a four-helix bundle connected to a carboxy-terminal immunoglobulin (Ig)-like domain through a beta-hairpin stabilized by disulfide bonds. Remarkably, different regions of Izumo1 display significant structural similarities to two proteins expressed by the invasive sporozoite stage of Plasmodium parasites: SPECT1, which is essential for host cell traversal and hepatocyte invasion [3]; and TRAP, which is necessary for gliding motility and invasion [4]. These observations suggest a link between the molecular mechanisms underlying host cell invasion by the malaria parasite and gamete membrane fusion at fertilization.
The structure of sperm Izumo1 reveals unexpected similarities with Plasmodium invasion proteins.,Nishimura K, Han L, Bianchi E, Wright GJ, de Sanctis D, Jovine L Curr Biol. 2016 Jul 25;26(14):R661-2. doi: 10.1016/j.cub.2016.06.028. Epub 2016, Jun 30. PMID:27374339[3]
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.
References
- ↑ Inoue N, Ikawa M, Isotani A, Okabe M. The immunoglobulin superfamily protein Izumo is required for sperm to fuse with eggs. Nature. 2005 Mar 10;434(7030):234-8. PMID:15759005 doi:http://dx.doi.org/10.1038/nature03362
- ↑ Bianchi E, Doe B, Goulding D, Wright GJ. Juno is the egg Izumo receptor and is essential for mammalian fertilization. Nature. 2014 Apr 24;508(7497):483-7. doi: 10.1038/nature13203. Epub 2014 Apr 16. PMID:24739963 doi:http://dx.doi.org/10.1038/nature13203
- ↑ Nishimura K, Han L, Bianchi E, Wright GJ, de Sanctis D, Jovine L. The structure of sperm Izumo1 reveals unexpected similarities with Plasmodium invasion proteins. Curr Biol. 2016 Jul 25;26(14):R661-2. doi: 10.1016/j.cub.2016.06.028. Epub 2016, Jun 30. PMID:27374339 doi:http://dx.doi.org/10.1016/j.cub.2016.06.028
