title: Characterization of a c-type heme-containing PAS sensor domain from Geobacter sulfurreducens representing a novel family of periplasmic sensors in Geobacteraceae and other bacteria.
abstract: Geobacter sulfurreducens encodes one of the largest numbers of proteins annotated as parts of the two-component signal transduction and/or chemotaxis pathways. Ten of these signal transducers have homologous periplasmic sensor domains that contain the sequence signature for c-type hemes. One such sensor domain encoded by gene GSU0303 was isolated and characterized. The protein was expressed in Escherichia coli and was isolated as two colored species (green and red). The green species is a monomer of the sensor domain with a five-coordinated high-spin heme and the red species is probably a noncovalent dimer of the sensor domain which might have an uncharacterized ligand bound to the dimer. The UV-VIS spectrum of the green species indicates that it has a c'-type heme, but its structure is predicted to be homologous to CitA, a periplasmic PAS domain that does not contain heme. The GSU0303 sensor domain represents a previously unreported family of PAS-type periplasmic sensor domains that contain c-type hemes; these proteins could be part of an important mechanism for sensing redox potential or small ligands in the periplasm. Homologs to the sensor domains we identified in G. sulfurreducens are observed in various bacteria although they occur in larger numbers in the Geobacteraceae.
authors.affiliation: Biosciences Division, Argonne National Laboratory, Argonne, IL, USA.
authors.forename: Yuri Y
authors.initials: YY
authors.lastname: Londer
authors.forename: Irina S
authors.initials: IS
authors.lastname: Dementieva
authors.forename: Cori A
authors.initials: CA
authors.lastname: D'Ausilio
authors.forename: P Raj
authors.initials: PR
authors.lastname: Pokkuluri
authors.forename: Marianne
authors.initials: M
authors.lastname: Schiffer
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry* / Q000235:genetics; D002633:Chemotaxis; D004926:Escherichia coli / Q000235:genetics; D045302:Geobacter / Q000235:genetics / Q000378:metabolism*; D006418:Heme / Q000737:chemistry*; D008969:Molecular Sequence Data; D005810:Multigene Family; D033903:Periplasmic Proteins / Q000737:chemistry* / Q000235:genetics; D010802:Phylogeny; D017434:Protein Structure, Tertiary; D016415:Sequence Alignment; D020539:Sequence Analysis, Protein; D015398:Signal Transduction; D013056:Spectrophotometry, Ultraviolet
chemical_list: D001426:Bacterial Proteins; D033903:Periplasmic Proteins; D006418:Heme