Fig. 6: CanX and AbpX belong to the TasA superfamily.

a pairwise profile HMM comparison of representative archaeal and bacterial cell-surface filament subunits. The heatmap shows HHsearch probabilities (%) for each pairwise comparison. The proteins are grouped into five categories: archaeal CanX proteins (arc CanX), archaeal and bacterial TasA-like proteins (arc & bac TasA-like), bacterial type I pilins (bac T1P), archaeal type IV pilins and archaellins (arc T4P & archaellins), and bacterial type IV pilins (bac T4P), all of which are β-sandwich/jelly-roll fold proteins that assemble into filaments. The NCBI/UniProt accession numbers of the proteins are provided in the “Methods” section; b distribution of the TasA superfamily across archaea, visualized on a species-level archaeal tree from the Genome Taxonomy Database. Colored dots indicate the presence of specific protein families: TasA/AbpX (blue), CanX (red), AbpA (green), and S. acidocaldarius 0406 thread (magenta). Phyla are indicated on the outer ring of the tree. Asgard Asgardarchaeota, Methano Methanobacteriota, Met B Methanobacteriota_B, Iain Iainarchaeota, and Aenigm Aenigmatarchaeota; c, d structural representations of representative TasA superfamily proteins. AlphaFold3 models are shown for selected proteins, while cryoEM structures are displayed for P. calidifontis AbpA (PDB: 7UEG) and the S. acidocaldarius 0406 thread subunit (PDB: 7PNB). β-helices are colored red, and β-strands are colored yellow.