5EJN

Crystal structure of Juno, the mammalian egg receptor for sperm Izumo1

  • Classification: CELL ADHESION
  • Organism(s): Mus musculus
  • Expression System: Homo sapiens

  • Deposited: 2015-11-02 Released: 2016-02-24 
  • Deposition Author(s): Nishimura, K., Han, L., Jovine, L.
  • Funding Organization(s): Karolinska Institutet; Swedish Research Council; Goran Gustafsson Foundation for Research in Natural Sciences and Medicine; Sven and Ebba-Christina Hagberg foundation; European Molecular Biology Organization; European Union 

Experimental Data Snapshot

  • Method: X-RAY DIFFRACTION
  • Resolution: 2.703 Å
  • R-Value Free: 0.248 
  • R-Value Work: 0.233 

wwPDB Validation 3D Report Full Report


This is version 1.1 of the entry. See complete history

Literature

Divergent evolution of vitamin B9 binding underlies Juno-mediated adhesion of mammalian gametes.

Han, L.Nishimura, K.Sadat Al Hosseini, H.Bianchi, E.Wright, G.J.Jovine, L.

(2016) Curr.Biol. 26: R100-R101

  • DOI: 10.1016/j.cub.2015.12.034
  • Also Cited By: 5B5K

  • PubMed Abstract: 
  • The interaction between egg and sperm is the first necessary step of fertilization in all sexually reproducing organisms. A decade-long search for a protein pair mediating this event in mammals culminated in the identification of the glycosylphosphat ...

    The interaction between egg and sperm is the first necessary step of fertilization in all sexually reproducing organisms. A decade-long search for a protein pair mediating this event in mammals culminated in the identification of the glycosylphosphatidylinositol (GPI)-anchored glycoprotein Juno as the egg plasma membrane receptor of sperm Izumo1 [1,2]. The Juno-Izumo1 interaction was shown to be essential for fertilization since mice lacking either gene exhibit sex-specific sterility, making these proteins promising non-hormonal contraceptive targets [1,3]. No structural information is available on how gamete membranes interact at fertilization, and it is unclear how Juno - which was previously named folate receptor (FR) 4, based on sequence similarity considerations - triggers membrane adhesion by binding Izumo1. Here, we report the crystal structure of Juno and find that the overall fold is similar to that of FRα and FRβ but with significant flexibility within the area that corresponds to the rigid ligand-binding site of these bona fide folate receptors. This explains both the inability of Juno to bind vitamin B9/folic acid [1], and why mutations within the flexible region can either abolish or change the species specificity of this interaction. Furthermore, structural similarity between Juno and the cholesterol-binding Niemann-Pick disease type C1 protein (NPC1) suggests how the modified binding surface of Juno may recognize the helical structure of the amino-terminal domain of Izumo1. As Juno appears to be a mammalian innovation, our study indicates that a key evolutionary event in mammalian reproduction originated from the neofunctionalization of the vitamin B9-binding pocket of an ancestral folate receptor molecule.


    Related Citations: 
    • Cross-species fertilization: the hamster egg receptor, Juno, binds the human sperm ligand, Izumo1.
      Bianchi, E.,Wright, G.J.
      (2015) Philos. Trans. R. Soc. Lond., B, Biol. Sci. 370: 20140101
    • Structural basis for molecular recognition of folic acid by folate receptors.
      Chen, C.,Ke, J.,Zhou, X.E.,Yi, W.,Brunzelle, J.S.,Li, J.,Yong, E.L.,Xu, H.E.,Melcher, K.
      (2013) Nature 500: 486
    • Structure of N-terminal domain of NPC1 reveals distinct subdomains for binding and transfer of cholesterol.
      Kwon, H.J.,Abi-Mosleh, L.,Wang, M.L.,Deisenhofer, J.,Goldstein, J.L.,Brown, M.S.,Infante, R.E.
      (2009) Cell 137: 1213
    • Juno is the egg Izumo receptor and is essential for mammalian fertilization.
      Bianchi, E.,Doe, B.,Goulding, D.,Wright, G.J.
      (2014) Nature 508: 483
    • Crystal structure of chicken riboflavin-binding protein.
      Monaco, H.L.
      (1997) EMBO J. 16: 1475
    • Structures of human folate receptors reveal biological trafficking states and diversity in folate and antifolate recognition.
      Wibowo, A.S.,Singh, M.,Reeder, K.M.,Carter, J.J.,Kovach, A.R.,Meng, W.,Ratnam, M.,Zhang, F.,Dann, C.E.
      (2013) Proc. Natl. Acad. Sci. U.S.A. 110: 15180


    Organizational Affiliation

    Department of Biosciences and Nutrition & Center for Innovative Medicine, Karolinska Institutet, Huddinge, SE-141 83, Sweden.




Macromolecules

Find similar proteins by: Sequence  |  Structure

Entity ID: 1
MoleculeChainsSequence LengthOrganismDetails
Sperm-egg fusion protein Juno
A, B
216Mus musculusMutation(s): 0 
Gene Names: Izumo1r (Folbp3, Folr4, Juno)
Find proteins for Q9EQF4 (Mus musculus)
Go to UniProtKB:  Q9EQF4
Small Molecules
Ligands 1 Unique
IDChainsName / Formula / InChI Key2D Diagram3D Interactions
NAG
Query on NAG

Download SDF File 
Download CCD File 
B
N-ACETYL-D-GLUCOSAMINE
C8 H15 N O6
OVRNDRQMDRJTHS-FMDGEEDCSA-N
 Ligand Interaction
Experimental Data & Validation

Experimental Data

  • Method: X-RAY DIFFRACTION
  • Resolution: 2.703 Å
  • R-Value Free: 0.248 
  • R-Value Work: 0.233 
  • Space Group: P 1 21 1
Unit Cell:
Length (Å)Angle (°)
a = 38.100α = 90.00
b = 52.200β = 90.00
c = 87.500γ = 90.00
Software Package:
Software NamePurpose
PHENIXrefinement
PHASERphasing
XDSdata scaling
XDSdata reduction
Cootmodel building

Structure Validation

View Full Validation Report or Ramachandran Plots



Entry History & Funding Information

Deposition Data


Funding OrganizationLocationGrant Number
Karolinska InstitutetSweden--
Swedish Research CouncilSweden2012-5093
Goran Gustafsson Foundation for Research in Natural Sciences and MedicineSweden--
Sven and Ebba-Christina Hagberg foundationSweden--
European Molecular Biology Organization--
European UnionERC 260759

Revision History 

  • Version 1.0: 2016-02-24
    Type: Initial release
  • Version 1.1: 2017-09-06
    Type: Author supporting evidence, Derived calculations