title: Exogenous 5,6-dimethylbenzimidazole caused production of a non-functional tetrachloroethene reductive dehalogenase in Sulfurospirillum multivorans.
abstract: Corrinoid-dependent reductive dehalogenation is mediated by phylogenetically diverse anaerobic bacteria that either synthesize corrinoids de novo or are dependent on corrinoid salvaging from the environment. The tetrachloroethene (PCE) reductive dehalogenase (PceA) of the Gram-negative Epsilonproteobacterium Sulfurospirillum multivorans harbours a norpseudo-B12 as corrinoid cofactor. Norpseudo-B12 differs from coenzyme B12 in the nucleotide loop structure. Adenine instead of 5,6-dimethylbenzimidazole (DMB) serves as lower ligand base of the central cobalt ion, and the nucleotide loop of norpseudo-B12 lacks a methyl group at position 176. In this study, S. multivorans was grown anaerobically with PCE in the presence of DMB. At a DMB concentration of 25 μM, the adenine moiety in the nucleotide loop of norpseudo-B12 was quantitatively replaced by DMB. The formation of the DMB-containing nor-B12 severely affected PCE-dependent growth and the PceA activity. In DMB-treated cells processing of the cytoplasmic PceA precursor was impeded, a result pointing to retarded cofactor incorporation. PceA enriched from cells cultivated with DMB contained nor-B12 . Nor-B12 purified from cells grown in the presence of DMB mediated the abiotic reductive dehalogenation of trichloroacetate to dichloroacetate at a 25-fold lower rate in comparison with norpseudo-B12 , a fact underpinning the relevance of norpseudo-B12 as efficient catalyst for reductive dehalogenation in general.
authors.affiliation: Department of Applied and Ecological Microbiology, Institute of Microbiology, Friedrich Schiller University, Philosophenweg 12, D-07743, Jena, Germany.
authors.forename: Sebastian
authors.initials: S
authors.lastname: Keller
authors.forename: Markus
authors.initials: M
authors.lastname: Ruetz
authors.forename: Cindy
authors.initials: C
authors.lastname: Kunze
authors.forename: Bernhard
authors.initials: B
authors.lastname: Kräutler
authors.forename: Gabriele
authors.initials: G
authors.lastname: Diekert
authors.forename: Torsten
authors.initials: T
authors.lastname: Schubert
mesh_terms: D001562:Benzimidazoles / Q000378:metabolism*; D003038:Cobamides / Q000096:biosynthesis / Q000737:chemistry; D045728:Corrinoids / Q000096:biosynthesis; D020565:Epsilonproteobacteria / Q000201:enzymology* / Q000254:growth & development; D010088:Oxidoreductases / Q000378:metabolism*
chemical_list: D001562:Benzimidazoles; D003038:Cobamides; D045728:Corrinoids; C015158:5,6-dimethylbenzimidazole; D010088:Oxidoreductases; C112990:tetrachloroethene dehalogenase