Crystal structure of the trimeric ectodomain of archaeal Fusexin1 (Fsx1)

Experimental Data Snapshot

  • Resolution: 2.30 Å
  • R-Value Free: 0.243 
  • R-Value Work: 0.199 
  • R-Value Observed: 0.200 

wwPDB Validation   3D Report Full Report

This is version 1.2 of the entry. See complete history


Discovery of archaeal fusexins homologous to eukaryotic HAP2/GCS1 gamete fusion proteins.

Moi, D.Nishio, S.Li, X.Valansi, C.Langleib, M.Brukman, N.G.Flyak, K.Dessimoz, C.de Sanctis, D.Tunyasuvunakool, K.Jumper, J.Grana, M.Romero, H.Aguilar, P.S.Jovine, L.Podbilewicz, B.

(2022) Nat Commun 13: 3880-3880

  • DOI: https://doi.org/10.1038/s41467-022-31564-1
  • Primary Citation of Related Structures:  

  • PubMed Abstract: 

    Sexual reproduction consists of genome reduction by meiosis and subsequent gamete fusion. The presence of genes homologous to eukaryotic meiotic genes in archaea and bacteria suggests that DNA repair mechanisms evolved towards meiotic recombination. However, fusogenic proteins resembling those found in gamete fusion in eukaryotes have so far not been found in prokaryotes. Here, we identify archaeal proteins that are homologs of fusexins, a superfamily of fusogens that mediate eukaryotic gamete and somatic cell fusion, as well as virus entry. The crystal structure of a trimeric archaeal fusexin (Fusexin1 or Fsx1) reveals an archetypical fusexin architecture with unique features such as a six-helix bundle and an additional globular domain. Ectopically expressed Fusexin1 can fuse mammalian cells, and this process involves the additional globular domain and a conserved fusion loop. Furthermore, archaeal fusexin genes are found within integrated mobile elements, suggesting potential roles in cell-cell fusion and gene exchange in archaea, as well as different scenarios for the evolutionary history of fusexins.

  • Organizational Affiliation

    Instituto de Fisiología, Biología Molecular y Neurociencias (IFIBYNE-CONICET), Buenos Aires, Argentina.

Find similar proteins by:  (by identity cutoff)  |  3D Structure
Entity ID: 1
MoleculeChains Sequence LengthOrganismDetailsImage
A, B, C
524metagenomeMutation(s): 0 
Find proteins for C0HM55 (Uncultured archaeon)
Explore C0HM55 
Go to UniProtKB:  C0HM55
Entity Groups  
Sequence Clusters30% Identity50% Identity70% Identity90% Identity95% Identity100% Identity
UniProt GroupC0HM55
Sequence Annotations
  • Reference Sequence
Small Molecules
Ligands 3 Unique
IDChains Name / Formula / InChI Key2D Diagram3D Interactions
Query on CA

Download Ideal Coordinates CCD File 
AA [auth B]
AB [auth C]
BA [auth B]
BB [auth C]
CA [auth B]
AA [auth B],
AB [auth C],
BA [auth B],
BB [auth C],
CA [auth B],
CB [auth C],
D [auth A],
DA [auth B],
DB [auth C],
E [auth A],
EA [auth B],
EB [auth C],
F [auth A],
FA [auth B],
FB [auth C],
G [auth A],
GA [auth B],
GB [auth C],
H [auth A],
HA [auth B],
I [auth A],
IA [auth B],
J [auth A],
JA [auth B],
K [auth A],
KA [auth B],
L [auth A],
M [auth A],
N [auth A],
YA [auth C],
ZA [auth C]
Query on CL

Download Ideal Coordinates CCD File 
KB [auth C]
LB [auth C]
MB [auth C]
NB [auth C]
OB [auth C]
KB [auth C],
LB [auth C],
MB [auth C],
NB [auth C],
OB [auth C],
PB [auth C],
QB [auth C],
RA [auth B],
SA [auth B],
T [auth A],
TA [auth B],
U [auth A],
UA [auth B],
V [auth A],
VA [auth B],
W [auth A],
WA [auth B],
X [auth A],
XA [auth B],
Y [auth A],
Z [auth A]
Query on NA

Download Ideal Coordinates CCD File 
HB [auth C]
IB [auth C]
JB [auth C]
LA [auth B]
MA [auth B]
HB [auth C],
IB [auth C],
JB [auth C],
LA [auth B],
MA [auth B],
NA [auth B],
O [auth A],
OA [auth B],
P [auth A],
PA [auth B],
Q [auth A],
QA [auth B],
R [auth A],
S [auth A]
Experimental Data & Validation

Experimental Data

  • Resolution: 2.30 Å
  • R-Value Free: 0.243 
  • R-Value Work: 0.199 
  • R-Value Observed: 0.200 
  • Space Group: C 1 2 1
Unit Cell:
Length ( Å )Angle ( ˚ )
a = 262.51α = 90
b = 111.33β = 100.709
c = 68.51γ = 90
Software Package:
Software NamePurpose
MxCuBEdata collection
XDSdata reduction
XSCALEdata scaling
Cootmodel building

Structure Validation

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Entry History & Funding Information

Deposition Data

Funding OrganizationLocationGrant Number
Swedish Research CouncilSweden2016-03999
Swedish Research CouncilSweden2020-04936
Knut and Alice Wallenberg FoundationSweden2018.0042

Revision History  (Full details and data files)

  • Version 1.0: 2022-07-13
    Type: Initial release
  • Version 1.1: 2024-03-27
    Changes: Data collection, Database references
  • Version 1.2: 2024-05-01
    Changes: Refinement description