9IHH

Ex vivo spore-silk A-ENA fibers

Summary for 9IHH

• Entry DOI: 10.2210/pdb9ihh/pdb
• EMDB information: 52871
• Descriptor: Ex vivo spore-silk A-ENA fibers (2 entities in total)
• Functional Keywords: endospore, isopeptide bond, a-ena, cross-linked, protein fiber, autocatalytic, protein fibril
• Biological source: Bacillus thuringiensis serovar israelensis
• Total number of polymer chains: 29
• Total formula weight: 316608.95

Authors

Sleutel, M.,Sogues, A.,Remaut, H. (deposition date: 2025-02-21, release date: 2026-03-04, Last modification date: 2026-04-01)

Primary citation

Sleutel, M.,Sogues, A.,Remaut, H.
Auto-crosslinking sporesilk fibers promote endospore and Cry toxin clustering.
Nat Commun, 2026

PubMed Abstract: Bacillus thuringiesis infects and kills insect larvae via its spores and associated entomotoxin-containing parasporal bodies (PSBs). We show that endospores and PSBs of B. thuringiensis Sv. Israëlensis are covered in a 'sporesilk' matrix that consist of 8 nm wide fibers with a double helical symmetry, formed by protofilaments of stacked alphahelical hairpins. These alpha endospore appendages ('A-ENA') are stabilized by up to ten autocatalytic and proximity-induced intermolecular isopeptide bonds per subunit, forming a continuous covalent polymer with remarkable chemical and physical robustness. We show A-ENA functions as B. thuringiensis virulence factor, increasing insecticidal activity by clustering spores and PSBs into an infectious clumps. Moreover, we demonstrate the recombinant production and self-assembly of A-ENA nanofibers, and show that the exogenic addition of A-ENA fibers to B. thuringiensis strains natively lacking sporesilks results in spore-PSB clustering and gain of virulence, enabling the rational, non-GMO functionalization of these biological pest control agents.

PubMed: 41813682
DOI: 10.1038/s41467-026-70495-z

Experimental method

ELECTRON MICROSCOPY (2.1 Å)