23SQ | pdb_000023sq

TamA complex with TamB DUF490 in detergent micelles.

• PDB DOI: https://doi.org/10.2210/pdb23SQ/pdb
• EM Map EMD-69220: EMDB EMDataResource

• Classification: MEMBRANE PROTEIN
• Organism(s): Escherichia coli
• Expression System: Escherichia coli
• Mutation(s): No 


• Deposited: 2026-02-16 Released: 2026-06-03 
• Deposition Author(s): Adamson, L.S.R., Doyle, M.T., Grosas, A.B.
• Funding Organization(s): Australian Research Council (ARC)

---

Experimental Data Snapshot

• Method: ELECTRON MICROSCOPY
• Resolution: 3.51 Å
• Aggregation State: PARTICLE 
• Reconstruction Method: SINGLE PARTICLE 

Literature

Mechanism of phospholipid transport to the bacterial outer membrane by TAM.

Eisenhuth, A.G., Adamson, L.S.R., Zhang, C., Abbas, G.S.K., North, R.A., Leyton, D.L., Bernstein, H.D., Brown, S.H.J., Stewart, A.G., Bailey, C.B., Don, A.S., Grosas, A.B., Doyle, M.T.

(2026) bioRxiv 

• PubMed: 42051294 
• DOI: https://doi.org/10.64898/2026.03.22.713439
• Primary Citation Related Structures: 
  23SP, 23SQ


• PubMed Abstract: 
  

  Gram-negative bacteria transport phospholipids from the inner membrane (IM) to the outer membrane (OM) via poorly understood processes. These processes are essential for cell growth and the establishment of an antibiotic-resistant barrier. Here, we conducted single-particle cryo-electron microscopy, in vivo functional assays, and lipidomics to investigate the role of the "translocation and assembly module" (TAM) in lipid transport. We found that the OM-embedded subunit TamA anchors the IM-embedded bridge-like subunit TamB to the OM by forming a functional stable hybrid-barrel structure with the highly conserved C-terminal domain of unknown function 490 (DUF490). Using in vivo disulfide-tethering experiments we found that a highly conserved amphipathic helix within TamB DUF490 is important for TAM to function in OM maintenance. We also found that TamB DUF490 forms a β-taco channel containing lipid-like densities and that the lipophilic property of the channel is important for TAM to maintain the levels of cardiolipin in the OM. Not only do our data support a novel model in which TAM acts to direct specific lipid classes into the OM, but it also supports the notion that TamB is a bacterial evolutionary prototype of a structurally homologous superfamily of eukaryotic bridge-like lipid transfer proteins.

---

Organizational Affiliation: 
• Centre for Drug Discovery Innovation, The University of Sydney, Sydney, NSW, Australia.
Sydney Infectious Diseases Institute, Faculty of Medicine and Health, The University of Sydney, Sydney, NSW, Australia.
School of Medical Sciences, Faculty of Medicine and Health, The University of Sydney, Sydney, NSW, Australia.
Charles Perkins Centre, The University of Sydney, Sydney, NSW, Australia.
School of Chemistry, The University of Sydney, Sydney, NSW, Australia.
Research School of Biology, Australian National University, Canberra, ACT, Australia.
Genetics and Biochemistry Branch, National Institute of Diabetes and Digestive and Kidney Diseases / National Institutes of Health, Bethesda, MD, USA.
School of Science, Molecular Horizons, and the Australian Research Council Centre for Cryo-electron Microscopy of Membrane Proteins, University of Wollongong, Wollongong, NSW, Australia.
Molecular, Structural and Computational Biology Division, The Victor Chang Cardiac Research Institute, Darlinghurst, NSW, Australia.
School of Clinical Medicine, Faculty of Medicine and Health, UNSW Sydney, Sydney, NSW, Australia.

Biological Assembly 1  

Global Symmetry: Asymmetric - C1 
Global Stoichiometry: Hetero 2-mer - A1B1 

Biological assembly 1 assigned by authors.

Biological Assembly Evidence: electron microscopy

Macromolecule Content 

• Total Structure Weight: 112.96 kDa 
• Atom Count: 7,627 
• Modeled Residue Count: 978 
• Deposited Residue Count: 1,027 
• Unique protein chains: 2

Macromolecules

Entity ID: 1
Molecule	Chains	Sequence Length	Organism	Details	Image
Translocation and assembly module subunit TamB	A [auth B]	455	Escherichia coli	Mutation(s): 0  Gene Names: tamB, ytfN, ytfO, b4221, JW4180
UniProt
Find proteins for P39321 (Escherichia coli (strain K12)) Explore P39321  Go to UniProtKB:  P39321

Entity ID: 2
Molecule	Chains	Sequence Length	Organism	Details	Image
Translocation and assembly module subunit TamA	B [auth A]	572	Escherichia coli	Mutation(s): 0  Gene Names: tamA, yftM, ytfM, b4220, JW4179
UniProt
Find proteins for P0ADE4 (Escherichia coli (strain K12)) Explore P0ADE4  Go to UniProtKB:  P0ADE4

Experimental Data & Validation

Experimental Data

• Method: ELECTRON MICROSCOPY
• Resolution: 3.51 Å
• Aggregation State: PARTICLE 
• Reconstruction Method: SINGLE PARTICLE 

EM Software:

Task	Software Package	Version
MODEL REFINEMENT	PHENIX	1.21.2_5419
RECONSTRUCTION	cryoSPARC	4.7.0

Structure Validation

Entry History 

& Funding Information

Deposition Data

• Released Date: 2026-06-03 
Deposition Author(s): Adamson, L.S.R., Doyle, M.T., Grosas, A.B.

---

Funding Organization	Location	Grant Number
Australian Research Council (ARC)	Australia	DP260100880

Revision History  

• Version 1.0: 2026-06-03
  Type: Initial release