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Structural Basis of a Novel Heme Binding Bacterial One-Component Switch

ABSTRACT: One-component systems (OCSs) integrate sensory and effector functions within a single protein, enabling rapid gene expression changes in response to environmental cues. Here, we characterized FG214, a heme binding OCS transcription factor from Fimbriimonas ginsengisoli. The Per-ARNT-Sim (PAS) domain of FG214 binds a hexacoordinate heme b in oxidized conditions and undergoes redox and ligand-dependent conformational changes, transitioning from a monomeric state to an active homodimer. Spectroscopic and structural data reveal that oxidation stabilizes the Helix-Turn-Helix (HTH)-PAS intramolecular domain interface, while reduction of the heme iron promotes HTH dissociation. Furthermore, addition of imidazole as a ferric heme ligand drives homodimerization and DNA binding. A 1.47 Å crystal structure of an imidazole-bound truncated construct captured an activated dimer, revealing heme coordination sites and homodimerization interfaces. Using DNA-binding assays, we identified an artificial promoter sequence and demonstrated ligand-enhanced protein-DNA binding. Additionally, we performed proof of concept experiments to showcase the ability of FG214 to homodimerize in vivo, setting the stage for a redox or gas sensitive biosensor. Together, these findings define FG214 as a novel heme-binding PAS transcription factor and establish a model for a redox-regulated molecular switches.

ORGANISM(S): synthetic construct Fimbriimonas ginsengisoli

PROVIDER: GSE319048 | GEO | 2026/03/15

REPOSITORIES: GEO

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