Extended Data Fig. 7: PflC is a homolog of serine protease HtrA but lacking a catalytic triad.

(a) Needleman-Wunsch global sequence alignments of Campylobacter jejuni PflC_N and PflC_C with C. jejuni HtrA from ChimeraX MatchMaker⁹¹ using default parameters. Asterisks highlight HtrA His-Asp-Ser catalytic triad not conserved in PflC. Coloured boxes indicate pruned residue pairs between PflC_N:HtrA_N (red) and PflC_C:HtrA_C (green) from MatchMaker algorithm using a 4 Å RMSD cutoff (b) Core folds of PflC and HtrA from ChimeraX structural alignment using pruned residue pairs of PflC_N and PflC_N (left) to HtrA (right) (PDBID: 6Z05³⁶) guided by the global alignment in panel A. Pruned core residues are depicted in colour, while non-core residues are depicted in grey. (c) RMSD of PflC alignment to HtrA depicted on the structure of PflC as worm diameter and colour (blue: 0 Å, white: 4 Å, red: 8 Å). (d) Left panel shows PflC and HtrA oriented as with the PflC protomer in Fig. 3c Right panels depict PflC and HtrA rotated similarly to reveal the HtrA active site cleft. Close-up boxes include stick representation of residues, highlighting HtrA’s H119:D150:S224 catalytic triad, and PflC’s N65 and S122 residues that sequence align to D150 and S224, revealing divergence and atrophy of the active site region in PflC.