Letter | Published:

Structure of IZUMO1–JUNO reveals sperm–oocyte recognition during mammalian fertilization

Nature volume 534, pages 566569 (23 June 2016) | Download Citation

Abstract

Fertilization is a fundamental process in sexual reproduction, creating a new individual through the combination of male and female gametes1,2,3,4. The IZUMO1 sperm membrane protein5 and its counterpart oocyte receptor JUNO6 have been identified as essential factors for sperm–oocyte interaction and fusion. However, the mechanism underlying their specific recognition remains poorly defined. Here, we show the crystal structures of human IZUMO1, JUNO and the IZUMO1–JUNO complex, establishing the structural basis for the IZUMO1–JUNO-mediated sperm–oocyte interaction. IZUMO1 exhibits an elongated rod-shaped structure comprised of a helical bundle IZUMO domain and an immunoglobulin-like domain that are each firmly anchored to an intervening β-hairpin region through conserved disulfide bonds. The central β-hairpin region of IZUMO1 provides the main platform for JUNO binding, while the surface located behind the putative JUNO ligand binding pocket is involved in IZUMO1 binding. Structure-based mutagenesis analysis confirms the biological importance of the IZUMO1–JUNO interaction. This structure provides a major step towards elucidating an essential phase of fertilization and it will contribute to the development of new therapeutic interventions for fertility, such as contraceptive agents.

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Accessions

Data deposits

The coordinates and structure-factor data of human IZUMO1, JUNO (form 1 and form 2), IZUMO1-JUNO complex (form 1, form 2, and form3) have been deposited in the Protein Data Bank under the accession numbers 5JK9, 5JKA, 5JKB, 5JKC, 5JKD and 5JKE, respectively.

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Acknowledgements

We thank the beamline staff members at the Photon Factory and SPring-8 for their assistance with data collection. We thank Y. Yamada and D. Liebschner for assistance with S-SAD data collection at PF-1A. This research is supported by the Platform Project for Supporting in Drug Discovery and Life Science Research (Platform for Drug Discovery, Informatics, and Structural Life Science) from the Japan Agency for Medical Research and Development (AMED). This work was supported by a Grant-in-Aid from the Japanese Ministry of Education, Culture, Sports, Science, and Technology (U.O., S.U., N.I. and T.S.); CREST, JST (T.S.); the Takeda Science Foundation (U.O., N.I. and T.S.); the Mochida Memorial Foundation for Medical and Pharmaceutical Research (U.O.); and the Daiichi Sankyo Foundation of Life Science (U.O.).

Author information

Author notes

    • Umeharu Ohto
    •  & Hanako Ishida

    These authors contributed equally to this work.

Affiliations

  1. Graduate School of Pharmaceutical Sciences, The University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113-0033, Japan

    • Umeharu Ohto
    • , Hanako Ishida
    •  & Toshiyuki Shimizu
  2. Graduate School of Engineering, Osaka University, 2-1 Yamadaoka, Suita 565-0871, Japan

    • Elena Krayukhina
    •  & Susumu Uchiyama
  3. Okazaki Institute for Integrative Bioscience, National Institutes of Natural Sciences, 5-1 Higashiyama, Myodaiji, Okazaki, Aichi 444-8787, Japan

    • Susumu Uchiyama
  4. Department of Cell Science, Institute of Biomedical Sciences, School of Medicine, Fukushima Medical University, 1 Hikarigaoka, Fukushima City, Fukushima 960-1295, Japan

    • Naokazu Inoue

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Contributions

H.I. expressed and purified recombinant proteins and performed size-exclusion chromatography and isothermal titration calorimetry experiments. H.I. and U.O. performed crystallization and structure determination. E.K and S.U performed AUC analyses. N.I. performed cellular assays. U.O and T.S. directed the research and wrote the paper with assistance from all other authors.

Competing interests

The authors declare no competing financial interests.

Corresponding authors

Correspondence to Umeharu Ohto or Toshiyuki Shimizu.

Reviewer Information Nature thanks K. Melcher, M. Okabe and the other anonymous reviewer(s) for their contribution to the peer review of this work.

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    Supplementary Information

    This file contains the uncropped blots with size marker indications.

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DOI

https://doi.org/10.1038/nature18596

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