9BAC | pdb_00009bac

Cryo-EM of Hyper2 tube, ~24 nm diameter

• PDB DOI: https://doi.org/10.2210/pdb9BAC/pdb
• EM Map EMD-44404: EMDB EMDataResource

• Classification: PROTEIN FIBRIL
• Organism(s): Hyperthermus sp.
• Expression System: Escherichia coli BL21
• Mutation(s): No 


• Deposited: 2024-04-03 Released: 2025-04-09 
• Deposition Author(s): Sonani, R.R., Miller, J.G., Conticello, V., Egelman, E.H.
• Funding Organization(s): National Institutes of Health/National Institute of General Medical Sciences (NIH/NIGMS)

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Experimental Data Snapshot

• Method: ELECTRON MICROSCOPY
• Resolution: 3.40 Å
• Aggregation State: FILAMENT 
• Reconstruction Method: HELICAL 

Literature

Donor strand complementation and calcium ion coordination drive the chaperone-free polymerization of archaeal cannulae.

Sleutel, M., Sonani, R.R., Miller, J.G., Wang, F., Gonzalez Socorro, A., Chen, Y., Martin, R., Demeler, B., Rudolph, M.J., Alva, V., Remaut, H., Egelman, E.H., Conticello, V.P.

(2025) Nat Commun 16: 9082-9082

• PubMed: 41083437 
• DOI: https://doi.org/10.1038/s41467-025-64120-8
• Primary Citation of Related Structures:  
  9BAB, 9BAC


• PubMed Abstract: 
  

  Cannulae are structurally rigid tubular protein filaments that accumulate on the extracellular surface of archaea within the family Pyrodictiaceae during cell growth. These obligate anaerobes propagate under hyperthermophilic conditions in which cannulae form a biomatrix that interconnects and sustains cells. The persistence of cannulae in this environment suggests that these filaments display significant thermostability, which has attracted technological interest in their development as synthetic protein-based biomaterials. Here, we report cryoEM structural analyses of ex vivo and in vitro assembled recombinant cannulae. We demonstrate that the interactions between protomers in native and recombinant cannulae is based on donor strand complementation (DSC), a form of non-covalent polymerization previously observed for bacterial chaperone-usher pili. Unexpectedly, calcium ion coordination at the subunit interfaces reinforces the network of donor strand interactions in the cannulae. This study provides insight into the mechanism of assembly of cannulae and the structural origin of their high stability and rigidity.

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Organizational Affiliation: 
• Structural Biology Brussels, Vrije Universiteit Brussel, Brussels, Belgium.
Structural and Molecular Microbiology, VIB-VUB Center for Structural Biology, Brussels, Belgium.
Department of Biochemistry and Molecular Genetics, University of Virginia, Charlottesville, VA, USA.
Department of Chemistry, Emory University, Atlanta, GA, USA.
New York Structural Biology Center, New York, NY, USA.
Biochemistry and Molecular Genetics Department, University of Alabama at Birmingham, Birmingham, AL, USA.
Department of Chemistry and Biochemistry, University of Lethbridge, Lethbridge, AB, Canada.
Department of Protein Evolution, Max Planck Institute for Biology Tübingen, Tübingen, Germany.
Structural Biology Brussels, Vrije Universiteit Brussel, Brussels, Belgium. [e-mail].
Structural and Molecular Microbiology, VIB-VUB Center for Structural Biology, Brussels, Belgium. [e-mail].
Department of Biochemistry and Molecular Genetics, University of Virginia, Charlottesville, VA, USA. [e-mail].
Department of Chemistry, Emory University, Atlanta, GA, USA. [e-mail].
The Robert P. Apkarian Integrated Electron Microscopy Core (IEMC), Emory University, Atlanta, GA, USA. [e-mail].

Biological Assembly 1  

Global Symmetry: Helical - H  (Explore in 3D)
Global Stoichiometry: Homo 66-mer - A66 

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

Biological Assembly Evidence: electron microscopy

Macromolecule Content 

• Total Structure Weight: 16.35 kDa 
• Atom Count: 1,142 
• Modeled Residue Count: 147 
• Deposited Residue Count: 148 
• Unique protein chains: 1

Macromolecules

Entity ID: 1
Molecule	Chains	Sequence Length	Organism	Details	Image
DUF1102 domain-containing protein	A [auth z]	148	Hyperthermus sp.	Mutation(s): 0  Gene Names: DSY37_03180
UniProt
Find proteins for A0A0V8RWX1 (Pyrodictium occultum) Explore A0A0V8RWX1  Go to UniProtKB:  A0A0V8RWX1

Small Molecules

Ligands 1 Unique
ID	Chains	Name / Formula / InChI Key	2D Diagram
CA (Subject of Investigation/LOI)	B [auth z], C [auth z], D [auth z]	CALCIUM ION Ca BHPQYMZQTOCNFJ-UHFFFAOYSA-N

Experimental Data & Validation

Experimental Data

• Method: ELECTRON MICROSCOPY
• Resolution: 3.40 Å
• Aggregation State: FILAMENT 
• Reconstruction Method: HELICAL 

EM Software:

Task	Software Package	Version
MODEL REFINEMENT	PHENIX	1.15.2_3472:

Structure Validation

Entry History & Funding Information

Deposition Data

• Released Date: 2025-04-09 
Deposition Author(s): Sonani, R.R., Miller, J.G., Conticello, V., Egelman, E.H.

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Funding Organization	Location	Grant Number
National Institutes of Health/National Institute of General Medical Sciences (NIH/NIGMS)	United States	GM122150

Revision History  

• Version 1.0: 2025-04-09
  Type: Initial release
  
• Version 1.1: 2025-10-29
  Changes: Data collection, Database references