The structure of sperm Izumo1 reveals unexpected similarities with Plasmodium invasion proteins.

Kaoru Nishimura, Ling Han, Enrica Bianchi, Gavin J Wright, Daniele de Sanctis, Luca Jovine

Research output: Contribution to journalArticlepeer-review


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 β-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. Copyright © 2016 The Authors. Published by Elsevier Ltd.. All rights reserved.
Original languageEnglish
Pages (from-to)R661-R662
Number of pages2
JournalCurrent Biology
Issue number14
Early online date30 Jun 2016
Publication statusPublished - 25 Jul 2016

Cite this