9T3P

Nonameric Ena1C ring of Bacillus cereus

Summary for 9T3P

• Entry DOI: 10.2210/pdb9t3p/pdb
• EMDB information: 55504
• Descriptor: DUF3992 domain-containing protein (1 entity in total)
• Functional Keywords: s-ena, ena anchoring, spore coat anchoring, endospore, protein fibril
• Biological source: Bacillus paranthracis
• Total number of polymer chains: 9
• Total formula weight: 170364.19

Authors

Sleutel, M.,Remaut, H. (deposition date: 2025-10-28, release date: 2025-12-03, Last modification date: 2026-03-04)

Primary citation

Zegeye, E.D.,Sleutel, M.,Jonsmoen, U.L.,Chen, J.,Morawska, L.P.,Mekonnen, Y.B.,Kuipers, O.P.,Remaut, H.,Aspholm, M.
Spatiotemporal expression of endospore appendages and cryo-EM insights into Ena1C-mediated S-ENA anchoring in Bacillus paranthracis.
Sci Rep, 16:7122-7122, 2026

PubMed Abstract: The endospores of many group species are decorated with highly resilient fibrous structures known as endospore appendages (ENAs), whose precise biological functions remain poorly understood. Structural and genetic studies have identified , , and as essential for forming the longer, thicker, and most abundant staggered (S)-ENA fibers in , whereas encodes the major subunit of the shorter, thinner, ladder-like (L)-ENAs. Here, we investigated the spatiotemporal expression dynamics of S- and L-ENA proteins and the specific role of Ena1C in S-ENA biogenesis. Using time-lapse fluorescence microscopy, we observed strict temporal regulation of gene expression, with no detectable ENA subunit production before spores became phase-bright. ENAs expression peaked during late sporulation phase, with fluorescence localized around the developing spore until its release; notably, S-ENA subunit expression began approximately one hour earlier than that of L-ENA subunits. Combining cryo-EM, negative-stain transmission electron microscopy, and genetic analyses, we show that Ena1C forms a nonameric ring-like structure required for tethering S-ENA to the spore surface. These findings provide new insights into the regulation of ENAs’ expression during fiber biogenesis and highlight their temporal coordination with spore coat and exosporium development.

PubMed: 41634327
DOI: 10.1038/s41598-026-38321-0

Experimental method

ELECTRON MICROSCOPY (3 Å)