9SJ2

Calcium coordinated ABPX fibers from Pyrodictium abyssi

Summary for 9SJ2

• Entry DOI: 10.2210/pdb9sj2/pdb
• EMDB information: 54935
• Descriptor: AbpX, CALCIUM ION (2 entities in total)
• Functional Keywords: fiber; helical; filament; hyperthermophile; calcium binding; donor strand complementation; pyrodictium abyssi; extracellular matrix; biomatrix; sinusoidal filament, structural protein
• Biological source: Pyrodictium abyssi DSM 6158
• Total number of polymer chains: 5
• Total formula weight: 88062.26

Authors

Sleutel, M.,Sogues, A.,Remaut, H.,Conticello, V.,Socorro, A. (deposition date: 2025-08-29, release date: 2026-06-10, Last modification date: 2026-08-19)

Primary citation

Sleutel, M.,Sogues, A.,Gonzalez Socorro, A.,Cooman, V.,Fislage, M.,Nijhawan, A.K.,Zuo, X.,Alva, V.,Remaut, H.,Conticello, V.P.
Pyrodictium abyssi AbpX reveals a calcium-responsive family of microbial biomatrix proteins that form thermostable hydrogels.
Proc.Natl.Acad.Sci.USA, 123:e2600204123-e2600204123, 2026

PubMed Abstract: Evolutionary pressure on microbial communities propagating under extreme environmental conditions often results in unique structural adaptations to promote cell survival. Here, we report an investigation of AbpX, a biomatrix protein identified in cultures of the hyperthermophilic archaeon . Under ex vivo and in vitro conditions, AbpX assembles into a paracrystalline lattice composed of semiflexible fibrils. CryoEM analysis of recombinant AbpX fibrils reveals that the precursor protein polymerizes through donor strand complementation (DSC), a process previously reported for chaperone-usher fimbriae in Gram-negative bacteria. Unlike the latter DSC protein polymers, AbpX undergoes chaperone-free polymerization in the presence of calcium ions, which are sequestered at the donor strand-acceptor groove interface between protomers in the fibril. Using a combination of cryoEM and crystallographic information, a structural model is proposed for the AbpX lattice that provides insight into its potential role in biofilm formation. These findings suggest that calcium ion coordination may contribute to fibril assembly and preorganize fibrils for incorporation into the protein lattice. Bioinformatic analysis indicates that AbpX exemplifies a distinct and broadly distributed clade of calcium ion responsive biomatrix proteins within the TasA superfamily that can be fabricated into hydrogel biomaterials in vitro under environmentally benign conditions.

PubMed: 42308048
DOI: 10.1073/pnas.2600204123

Experimental method

ELECTRON MICROSCOPY (3.57 Å)