9SKK | pdb_00009skk

Polysaccharide co-polymerase FepE open 9 subunit complex

• PDB DOI: https://doi.org/10.2210/pdb9SKK/pdb
• EM Map EMD-54967: EMDB EMDataResource

• Classification: MEMBRANE PROTEIN
• Organism(s): Escherichia coli K-12
• Expression System: Escherichia coli DH5[alpha]
• Mutation(s): No 


• Deposited: 2025-09-02 Released: 2026-05-27 
• Deposition Author(s): Wiseman, B., Hogbom, M.
• Funding Organization(s): Swedish Research Council, Knut and Alice Wallenberg Foundation

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Experimental Data Snapshot

• Method: ELECTRON MICROSCOPY
• Resolution: 3.30 Å
• Aggregation State: PARTICLE 
• Reconstruction Method: SINGLE PARTICLE 

Starting Model: in silico

Literature

Structural Basis of Lipopolysaccharide O-Antigen Chain Length Modality.

Wiseman, B., Widmalm, G., Hogbom, M.

(2026) Research (Wash D C) 9: 1276-1276

• PubMed: 42131584 
• DOI: https://doi.org/10.34133/research.1276
• Primary Citation Related Structures: 
  9SKI, 9SKJ, 9SKK, 9SKL


• PubMed Abstract: 
  

  Lipopolysaccharides are important components of the gram-negative bacterial cell envelope that are involved in immune evasion and act as a protective barrier. Employing cryo-electron microscopy, we resolved the structure and dynamics of FepE, the copolymerase component of the Wzy-dependent pathway, responsible for the length modulation of very long O-antigen molecules. Comparison of the interior volumes of related copolymerases' periplasmic domains with the volume of hydrated sugars suggests that the size of the periplasmic domain controls the length of the O-antigen, implying that polysaccharide chain polymerization occurs inside the copolymerase periplasmic domain. Moreover, we show the opening of the FepE complex as well as other large mechanistically relevant movements. The opening of the complex presents an attractive corridor for the release of completed polysaccharide chains.

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Organizational Affiliation: 
• Department of Biochemistry and Biophysics and Science for Life Laboratory, Stockholm University, Stockholm, Sweden.
Department of Chemistry, Stockholm University, Stockholm, Sweden.

Biological Assembly 1  

Global Symmetry: Asymmetric - C1 
Global Stoichiometry: Homo 9-mer - A9 

Biological assembly 1 assigned by authors and generated by (software)

Biological Assembly Evidence: electron microscopy

Macromolecule Content 

• Total Structure Weight: 396.26 kDa 
• Atom Count: 22,904 
• Modeled Residue Count: 2,903 
• Deposited Residue Count: 3,528 
• Unique protein chains: 1

Macromolecules

Entity ID: 1
Molecule	Chains	Sequence Length	Organism	Details	Image
Ferric enterobactin transport protein FepE	A, B, C, D, E, F, G, H, I	392	Escherichia coli K-12	Mutation(s): 0  Gene Names: fepE, b0587, JW0579
UniProt
Find proteins for P26266 (Escherichia coli (strain K12)) Explore P26266  Go to UniProtKB:  P26266

Experimental Data & Validation

Experimental Data

• Method: ELECTRON MICROSCOPY
• Resolution: 3.30 Å
• Aggregation State: PARTICLE 
• Reconstruction Method: SINGLE PARTICLE 

EM Software:

Task	Software Package	Version
RECONSTRUCTION	cryoSPARC	4.7
MODEL REFINEMENT	PHENIX	1.21.2_5419:

Structure Validation

Entry History 

& Funding Information

Deposition Data

• Released Date: 2026-05-27 
Deposition Author(s): Wiseman, B., Hogbom, M.

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Funding Organization	Location	Grant Number
Swedish Research Council	Sweden	2021-043992
Knut and Alice Wallenberg Foundation	Sweden	2023.0201

Revision History  

• Version 1.0: 2026-05-27
  Type: Initial release