title: Molybdenum and tungsten in Campylobacter jejuni: their  physiological role and identification of separate transporters  regulated by a single ModE-like protein.
abstract: Campylobacter jejuni is an important human pathogen that causes millions of cases of food-borne enteritis each year. The C. jejuni respiratory chain is highly branched and contains at least four enzymes predicted to contain a metal binding pterin (MPT), with the metal being either molybdenum or tungsten. Also predicted are two separate transport systems, one for molybdenum encoded by modABC and a second for tungsten encoded by tupABC. Both transport systems were mutated and the activities of the four predicted MPT-containing enzymes were assayed in the presence of molybdenum and tungsten in wild-type and mod and tup backgrounds. Results indicate that mod is primarily a molybdenum transporter that can also transport tungsten, while tup is a tungsten-specific transporter. The MPT containing enzymes nitrate reductase, sulphite oxidase, and SN oxide reductase are strict molybdoenzymes while formate dehydrogenase prefers tungsten. A ModE-like protein regulates both transporters, repressing mod in the presence of both molybdenum and tungsten and tup only in the presence of tungsten. Like other ModE proteins, the C. jejuni ModE binds DNA through a helix-turn-helix DNA binding domain, but unlike other members of the ModE family it does not have a metal binding domain.
authors.affiliation: Department of Microbiology, North Carolina State University, Raleigh, NC 27695, USA.
authors.forename: Michael E
authors.initials: ME
authors.lastname: Taveirne
authors.forename: Michael L
authors.initials: ML
authors.lastname: Sikes
authors.forename: Jonathan W
authors.initials: JW
authors.lastname: Olson
mesh_terms: D018528:ATP-Binding Cassette Transporters / Q000235:genetics / Q000378:metabolism; D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D016123:Campylobacter jejuni / Q000235:genetics / Q000378:metabolism*; D004579:Electron Transport / Q000235:genetics; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism; D005560:Formate Dehydrogenases / Q000235:genetics / Q000378:metabolism; D006801:Humans; D026901:Membrane Transport Proteins / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D008982:Molybdenum / Q000737:chemistry / Q000378:metabolism*; D050901:Nitrate Reductase / Q000235:genetics / Q000378:metabolism; D050896:Nitrate Reductase (NAD(P)H) / Q000378:metabolism; D009565:Nitrate Reductases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D010802:Phylogeny; D015202:Protein Engineering; D011622:Pterins / Q000378:metabolism; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D014157:Transcription Factors / Q000378:metabolism*; D014414:Tungsten / Q000737:chemistry / Q000378:metabolism*
chemical_list: D018528:ATP-Binding Cassette Transporters; D001426:Bacterial Proteins; D026901:Membrane Transport Proteins; C101050:ModE protein, bacteria; D011622:Pterins; D014157:Transcription Factors; D008982:Molybdenum; D005560:Formate Dehydrogenases; D009565:Nitrate Reductases; D050896:Nitrate Reductase (NAD(P)H); D050901:Nitrate Reductase; D014414:Tungsten