8OTQ image
Entry Detail
PDB ID:
8OTQ
EMDB ID:
Title:
Cryo-EM structure of Strongylocentrotus purpuratus sperm-specific Na+/H+ exchanger SLC9C1 in GDN
Biological Source:
Host Organism:
PDB Version:
Deposition Date:
2023-04-21
Release Date:
2023-11-01
Method Details:
Experimental Method:
Resolution:
3.22 Å
Aggregation State:
PARTICLE
Reconstruction Method:
SINGLE PARTICLE
Macromolecular Entities
Polymer Type:polypeptide(L)
Description:Sperm-specific sodium proton exchanger
Chain IDs:A, B
Chain Length:1331
Number of Molecules:2
Biological Source:Strongylocentrotus purpuratus
Primary Citation
Structure and electromechanical coupling of a voltage-gated Na + /H + exchanger.
Nature 623 193 201 (2023)
PMID: 37880360 DOI: 10.1038/s41586-023-06518-2

Abstact

Voltage-sensing domains control the activation of voltage-gated ion channels, with a few exceptions1. One such exception is the sperm-specific Na+/H+ exchanger SLC9C1, which is the only known transporter to be regulated by voltage-sensing domains2-5. After hyperpolarization of sperm flagella, SLC9C1 becomes active, causing pH alkalinization and CatSper Ca2+ channel activation, which drives chemotaxis2,6. SLC9C1 activation is further regulated by cAMP2,7, which is produced by soluble adenyl cyclase (sAC). SLC9C1 is therefore an essential component of the pH-sAC-cAMP signalling pathway in metazoa8,9, required for sperm motility and fertilization4. Despite its importance, the molecular basis of SLC9C1 voltage activation is unclear. Here we report cryo-electron microscopy (cryo-EM) structures of sea urchin SLC9C1 in detergent and nanodiscs. We show that the voltage-sensing domains are positioned in an unusual configuration, sandwiching each side of the SLC9C1 homodimer. The S4 segment is very long, 90 Å in length, and connects the voltage-sensing domains to the cytoplasmic cyclic-nucleotide-binding domains. The S4 segment is in the up configuration-the inactive state of SLC9C1. Consistently, although a negatively charged cavity is accessible for Na+ to bind to the ion-transporting domains of SLC9C1, an intracellular helix connected to S4 restricts their movement. On the basis of the differences in the cryo-EM structure of SLC9C1 in the presence of cAMP, we propose that, upon hyperpolarization, the S4 segment moves down, removing this constriction and enabling Na+/H+ exchange.

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