Tungstate Uptake by a Highly Specific ABC Transporter inEubacterium acidaminophilum

Abstract

The Gram-positive anaerobe Eubacterium acidaminophilum contains at least two tungsten-dependent enzymes: viologen-dependent formate dehydrogenase and aldehyde dehydrogenase.185 W-Labeled tungstate was taken up by this organism with a maximum rate of 0.53 pmol min ؊1 mg ؊1 of protein at 36°C. The uptake was not affected by equimolar amounts of molybdate. The genes tupABC coding for an ABC transporter specific for tungstate were cloned in the downstream region of genes encoding a tungsten-containing formate dehydrogenase. The substrate-binding protein, TupA, of this putative transporter was overexpressed in Escherichia coli, and its binding properties toward oxyanions were determined by a native polyacrylamide gel retardation assay. Only tungstate induced a shift of TupA mobility, suggesting that only this anion was specifically bound by TupA. If molybdate and sulfate were added in high molar excess (>1000-fold), they were also slightly bound by TupA. The K d value for tungstate was determined to be 0.5 M. The genes encoding the tungstate-specific ABC transporter exhibited highest similarities to putative transporters from Methanobacterium thermoautotrophicum, Haloferax volcanii, Vibrio cholerae, and Campylobacter jejuni. These five transporters represent a separate phylogenetic group of oxyanion ABC transporters as evident from analysis of the deduced amino acid sequences of the binding proteins. Downstream of the tupABC genes, the genes moeA, moeA-1, moaA, and a truncated moaC have been identified by sequence comparison of the deduced amino acid sequences. They should participate in the biosynthesis of the pterin cofactor that is present in molybdenum-and tungstencontaining enzymes except nitrogenase.

High-Affinity Vanadate Transport System in the CyanobacteriumAnabaena variabilisATCC 29413

“…These genes have no similarity to other cyanobacterial transporters, suggesting that they were acquired by lateral transfer on April 27, 2019 by guest http://jb.asm.org/ from other bacteria. The vupABC genes are most similar to a family of putative tungstate transport genes, exemplified by the tupABC genes of E. acidaminophilum, which have been shown to be required for the transport of tungstate in that strain (31). The similarity of vupA/tupA and vupB/tupB is much higher (58% and 61%, respectively) than vupC/tupC (31%).…”

“…Tungstoenzymes, including dehydrogenases, hydratases, and oxidoreductases that catalyze the oxidation of aldehydes, contain a tungstopterin cofactor similar to molybdopterin and are more common in hyperthermophilic bacteria and archaea with anaerobic metabolism than are molybdoenzymes (16,21,24,28,(39)(40)(41)53). Eubacterium acidaminophilum has two tungstoenzymes, viologen-dependent formate dehydrogenase and aldehyde dehydrogenase, and tungstate uptake is mediated by a specific ABC transporter encoded by the tupABC genes (31,32). Similar putative tungstate transport genes have been identified in the genomes of many other bacteria, although tungstoenzymes have not been characterized in most of these strains.…”

Vanadium Requirements and Uptake Kinetics in the Dinitrogen-Fixing Bacterium Azotobacter vinelandii

“…What happens to V in the periplasmic space of A. vinelandii is not known, but the catechols azotochelin and protochelin have been shown to be involved in Mo uptake as well as V uptake (Bellenger et al, unpublished), and molybdate in the periplasm is transported by a well-characterized ABC-type transporter (19,23,28). Such transporters commonly are used for oxoanion uptake (21,28,30,32), and one recently was identified for vanadate transport in A. variabilis (27). If such a transport system also exists in A. vinelandii, V uptake may be very similar to Mo uptake.…”

Molecular Analysis of the Copper-Transporting Efflux System CusCFBA of Escherichia coli

“…CusF could act as a periplasmic copper chaperone shuttling copper to the CusCBA efflux complex and thereby increasing the accessibility of periplasmic copper. This function is reminiscent of periplasmic substrate binding proteins that shuttle their substrates to the MerT transporter or ABC uptake systems (25,27,30,36,43,48,51,52). Another small periplasmic copper-binding protein, the CopC protein from P. syringae, binds Cu(I) and Cu(II) to different sites, and redox change of the bound copper ion causes its migration from one site of CopC to the other (6).…”