8RKI image
Entry Detail
PDB ID:
8RKI
Title:
Molecular basis of ZP3/ZP1 heteropolymerization: crystal structure of a native vertebrate egg coat filament fragment
Biological Source:
Source Organism:
PDB Version:
Deposition Date:
2023-12-25
Release Date:
2024-03-13
Method Details:
Experimental Method:
Resolution:
4.20 Å
R-Value Free:
0.36
R-Value Work:
0.32
R-Value Observed:
0.33
Space Group:
P 31 2 1
Macromolecular Entities
Polymer Type:polypeptide(L)
Description:Zona pellucida sperm-binding protein 3
Chain IDs:A
Chain Length:320
Number of Molecules:1
Biological Source:Oryzias latipes
Polymer Type:polypeptide(L)
Description:Choriogenin H
Chain IDs:B
Chain Length:170
Number of Molecules:1
Biological Source:Oryzias latipes
Polymer Type:polypeptide(L)
Description:Choriogenin H
Chain IDs:C
Chain Length:167
Number of Molecules:1
Biological Source:Oryzias latipes
Ligand Molecules
Primary Citation

Abstact

Following the fertilization of an egg by a single sperm, the egg coat or zona pellucida (ZP) hardens and polyspermy is irreversibly blocked. These events are associated with the cleavage of the N-terminal region (NTR) of glycoprotein ZP2, a major subunit of ZP filaments. ZP2 processing is thought to inactivate sperm binding to the ZP, but its molecular consequences and connection with ZP hardening are unknown. Biochemical and structural studies show that cleavage of ZP2 triggers its oligomerization. Moreover, the structure of a native vertebrate egg coat filament, combined with AlphaFold predictions of human ZP polymers, reveals that two protofilaments consisting of type I (ZP3) and type II (ZP1/ZP2/ZP4) components interlock into a left-handed double helix from which the NTRs of type II subunits protrude. Together, these data suggest that oligomerization of cleaved ZP2 NTRs extensively cross-links ZP filaments, rigidifying the egg coat and making it physically impenetrable to sperm.

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Primary Citation of related structures