Cryo-EM structure of native human uromodulin, a zona pellucida module polymer.

Alena Stsiapanava,Luca Rampoldi,Luca Jovine,Ling Han,Marcel Bokhove,Martina Brunati,Marta Carroni,Hans Hebert,Chenrui Xu,Sara Zamora‐Caballero,Shigeki Yasumasu,Céline Schaeffer,Bin Wu

doi:10.15252/embj.2020106807

Abstract

Assembly of extracellular filaments and matrices mediating fundamental biological processes such as morphogenesis, hearing, fertilization, and antibacterial defense is driven by a ubiquitous polymerization module known as zona pellucida (ZP) “domain”. Despite the conservation of this element from hydra to humans, no detailed information is available on the filamentous conformation of any ZP module protein. Here, we report a cryo‐electron microscopy study of uromodulin (UMOD)/Tamm–Horsfall protein, the most abundant protein in human urine and an archetypal ZP module‐containing molecule, in its mature homopolymeric state. UMOD forms a one‐start helix with an unprecedented 180‐degree twist between subunits enfolded by interdomain linkers that have completely reorganized as a result of propeptide dissociation. Lateral interaction between filaments in the urine generates sheets exposing a checkerboard of binding sites to capture uropathogenic bacteria, and UMOD‐based models of heteromeric vertebrate egg coat filaments identify a common sperm‐binding region at the interface between subunits.

Highlights

The zona pellucida (ZP) module is a polymer building block of ~260 amino acids that fold into two topologically related immunoglobulin-like domains, ZP-N and ZP-C (Bokhove and Jovine, 2018; Bork and Sander, 1992; Jovine et al, 2002, 2004)
UMOD forms a one-start helix with an unprecedented 180-degree twist between subunits enfolded by interdomain linkers that have completely reorganized as a result of propeptide dissociation
The interdomain linker of the UMOD precursor is entirely structured by forming an α-helix (α1) and a β-strand (β1) that pack against ZP-C; this orients the ZP-N domain so that it homodimerizes with ZP-N from another molecule (Bokhove et al, 2016a)

Summary

Introduction

The ZP module is a polymer building block of ~260 amino acids that fold into two topologically related immunoglobulin-like domains, ZP-N and ZP-C (Bokhove and Jovine, 2018; Bork and Sander, 1992; Jovine et al, 2002, 2004). The interdomain linker of the UMOD precursor is entirely structured by forming an α-helix (α1) and a β-strand (β1) that pack against ZP-C; this orients the ZP-N domain so that it homodimerizes with ZP-N from another molecule (Bokhove et al, 2016a) Despite these differences, in both cases the last β-strand of ZP-C (βG) - generally referred to as the external hydrophobic patch (EHP) - is part of a polymerization-blocking C-terminal propeptide (CTP) whose protease-dependent release is required for protein incorporation into filaments (Jovine et al, 2004; Schaeffer et al, 2009). In both mammalian egg coat proteins and UMOD, this process is dependent on membrane anchoring of the precursors (Brunati et al, 2015; Jovine et al, 2002); it is unclear how propeptide dissociation triggers polymerization, and the molecular basis of ZP module-mediated protein assembly remains essentially unknown

Methods

Results

Discussion

Conclusion