Premium
A role for tungsten in the biology of Campylobacter jejuni : tungstate stimulates formate dehydrogenase activity and is transported via an ultra‐high affinity ABC system distinct from the molybdate transporter
Author(s) -
Smart Jonathan P.,
Cliff Matthew J.,
Kelly David J.
Publication year - 2009
Publication title -
molecular microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.857
H-Index - 247
eISSN - 1365-2958
pISSN - 0950-382X
DOI - 10.1111/j.1365-2958.2009.06902.x
Subject(s) - molybdate , biology , campylobacter jejuni , tungstate , formate dehydrogenase , biochemistry , isothermal titration calorimetry , atp binding cassette transporter , mutant , formate , thermus thermophilus , eubacterium , microbiology and biotechnology , transporter , escherichia coli , bacteria , chemistry , gene , inorganic chemistry , genetics , catalysis
Summary The food‐borne pathogen Campylobacter jejuni possesses no known tungstoenzymes, yet encodes two ABC transporters (Cj0300–0303 and Cj1538–1540) homologous to bacterial molybdate (ModABC) uptake systems and the tungstate transporter (TupABC) of Eubacterium acidaminophilum respectively. The actual substrates and physiological role of these transporters were investigated. Tryptophan fluorescence spectroscopy and isothermal titration calorimetry of the purified periplasmic binding proteins of each system revealed that while Cj0303 is unable to discriminate between molybdate and tungstate ( K D values for both ligands of 4–8 nM), Cj1540 binds tungstate with a K D of 1.0 ± 0.2 pM; 50 000‐fold more tightly than molybdate. Induction‐coupled plasma mass spectroscopy of single and double mutants showed that this large difference in affinity is reflected in a lower cellular tungsten content in a cj1540 ( tupA ) mutant compared with a cj0303c ( modA ) mutant. Surprisingly, formate dehydrogenase (FDH) activity was decreased ∼50% in the tupA strain, and supplementation of the growth medium with tungstate significantly increased FDH activity in the wild type, while inhibiting known molybdoenzymes. Our data suggest that C. jejuni possesses a specific, ultra‐high affinity tungstate transporter that supplies tungsten for incorporation into FDH. Furthermore, possession of two MoeA paralogues may explain the formation of both molybdopterin and tungstopterin in this bacterium.