MyJournals Home  

RSS FeedsHeme ligation and redox chemistry in two bacterial thiosulfate dehydrogenase (TsdA) enzymes [Bioenergetics] (Journal of Biological Chemistry)


22 november 2019 17:00:06

Heme ligation and redox chemistry in two bacterial thiosulfate dehydrogenase (TsdA) enzymes [Bioenergetics] (Journal of Biological Chemistry)

Thiosulfate dehydrogenases (TsdAs) are bidirectional bacterial di-heme enzymes that catalyze the interconversion of tetrathionate and thiosulfate at measurable rates in both directions. In contrast to our knowledge of TsdA activities, information on the redox properties in the absence of substrates is rather scant. To address this deficit, we combined magnetic CD (MCD) spectroscopy and protein film electrochemistry (PFE) in a study to resolve heme ligation and redox chemistry in two representative TsdAs. We examined the TsdAs from Campylobacter jejuni, a microaerobic human pathogen, and from the purple sulfur bacterium Allochromatium vinosum. In these organisms, the enzyme functions as a tetrathionate reductase and a thiosulfate oxidase, respectively. The active site Heme 1 in both enzymes has His/Cys ligation in the ferric and ferrous states and the midpoint potentials (Em) of the corresponding redox transformations are similar, -185 mV versus standard hydrogen electrode (SHE). However, fundamental differences are observed in the properties of the second, electron transferring, Heme 2. In C. jejuni, TsdA Heme 2 has His/Met ligation and an Em of +172 mV. In A. vinosum TsdA, Heme 2 reduction triggers a switch from His/Lys ligation (Em, -129 mV) to His/Met (Em, +266 mV), but the rates of interconversion are such that His/Lys ligation would be retained during turnover. In description, our findings have unambiguously assigned Em values to defined axial ligand sets in TsdAs, specified the rates of Heme 2 ligand exchange in the A. vinosum enzyme, and provided information relevant to describing their catalytic mechanism(s).

58 viewsCategory: Biochemistry
Staphylopine and pseudopaline dehydrogenase from bacterial pathogens catalyze reversible reactions and produce stereospecific metallophores [Protein Structure and Folding] (Journal of Biological Chemistry)
Withdrawal: DNA damage induces NF-{kappa}B-dependent microRNA-21 up-regulation and promotes breast cancer cell invasion. [Withdrawals/Retractions] (Journal of Biological Chemistry)
blog comments powered by Disqus
The latest issues of all your favorite science journals on one page


Register | Retrieve



Copyright © 2008 - 2020 Indigonet Services B.V.. Contact: Tim Hulsen. Read here our privacy notice.
Other websites of Indigonet Services B.V.: Nieuws Vacatures News Tweets Nachrichten