9BAC

Cryo-EM of Hyper2 tube, ~24 nm diameter

Summary for 9BAC

• Entry DOI: 10.2210/pdb9bac/pdb
• EMDB information: 44403 44404
• Descriptor: DUF1102 domain-containing protein, CALCIUM ION (2 entities in total)
• Functional Keywords: hyper2, protein tube, helical tube, strand donation, protein fibril
• Biological source: Hyperthermus sp.
• Total number of polymer chains: 1
• Total formula weight: 16354.51

Authors

Sonani, R.R.,Miller, J.G.,Conticello, V.,Egelman, E.H. (deposition date: 2024-04-03, release date: 2025-04-09, Last modification date: 2025-10-29)

Primary citation

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.
Donor strand complementation and calcium ion coordination drive the chaperone-free polymerization of archaeal cannulae.
Nat Commun, 16:9082-9082, 2025

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.

PubMed: 41083437
DOI: 10.1038/s41467-025-64120-8

Experimental method

ELECTRON MICROSCOPY (3.4 Å)