Key Bacterial Multi-Centered Metal Enzymes Involved in Nitrate and Sulfate Respiration

Adenylylsulfate reductase (adenosine 5-phosphosulfate [APS] reductase [APSR]) plays a key role in catalyzing APS to sulfite in dissimilatory sulfate reduction. Here, we report the crystal structure of APSR from Desulfovibrio gigas at 3.1-Å resolution. Different from the ␣ 2 ␤ 2 -heterotetramer of the Archaeoglobus fulgidus, the overall structure of APSR from D. gigas comprises six ␣␤-heterodimers that form a hexameric structure. The flavin adenine dinucleotide is noncovalently attached to the ␣-subunit, and two gigas and A. fulgidus shows the largest differences toward the C termini of the ␤-subunits, and structural comparison reveals notable differences at the C termini, activity sites, and other regions. The disulfide comprising Cys156 to Cys162 stabilizes the C-terminal loop of the ␤-subunit and is crucial for oligomerization. Dynamic light scattering and ultracentrifugation measurements reveal multiple forms of APSR upon the addition of AMP, indicating that AMP binding dissociates the inactive hexamer into functional dimers, presumably by switching the C terminus of the ␤-subunit away from the active site. The crystal structure of APSR, together with its oligomerization properties, suggests that APSR from sulfatereducing bacteria might self-regulate its activity through the C terminus of the ␤-subunit.Sulfate-reducing bacteria (SRB) are a special group of prokaryotes that are found in sulfate-rich environments because of their ability to metabolize sulfate. SRB use sulfate as the final electron acceptor in various anaerobic environments, such as soil, oil fields, the sea, or the innards of animals or even human beings (10,11,19,25,33). Their ability to degrade sulfate offers protection against environmental pollution. SRB can remove sulfate and toxic heavy atoms from factory waste waters (12). The Desulfovibrio species is a much-studied representative of SRB, and Desulfovibrio gigas has been studied under many diverse conditions to elucidate metabolic pathways (23,35).Sulfate reduction is one of the oldest forms of cellular metabolism. The reduction can be either assimilatory or dissimilatory. Sulfate is the terminal electron acceptor in dissimilatory reduction and the raw material for the biosynthesis of cysteine in assimilatory reduction. The latter type of reduction occurs in archaebacteria, bacteria, fungi, and plants via various pathways (17). For example, in Escherichia coli, the reduction initially catalyzes sulfate to adenosine 5Ј-phosphosulfate (APS) by ATP sulfurylase. APS is then phosphorylated by APS kinase to 3Ј-phosphate APS, which is then further reduced to sulfite by 3Ј-phosphate APS reductase (APSR). Finally, sulfite is reduced by sulfite reductase to sulfide, which condenses with O-acetylserine by O-acetylserine lyase to form cysteine. For comparison, in dissimilatory sulfate reduction, sulfate is first catalyzed by ATP sulfurylase to APS, which is then directly reduced by APSR to sulfite. Sulfite is subsequently reduced by dissimilatory sulfite reductase to the following three possible pro...

show abstract

“…3C). The overall structure of APSR can be grouped into the structure family of fumarate reductase (9,14).…”

Section: Resultsmentioning

confidence: 99%

Crystal Structure of Adenylylsulfate Reductase fromDesulfovibrio gigasSuggests a Potential Self-Regulation Mechanism Involving the C Terminus of the β-Subunit

et al. 2009

View full text Add to dashboard Cite

show abstract

“…Several SRP, including members of the genera Desulfovibrio, Desulfobulbus, Desulfotomaculum, Desulfobacterium and Thermodesulfovibrio, can respire nitrate using the process of nitrate ammonification (Fritz, Einsle, Rudolf, Schiffer, & Kroneck, 2005;Moura, González, Moura, & Fauque, 2007), where nitrate is converted to nitrite and this to ammonia (Simon & Klotz, 2013). Sulphate is usually reduced preferentially by SRP, despite nitrate being the thermodynamically more favourable electron acceptor (Marietou, Griffiths, & Cole, 2009).…”

Section: Other Electron Acceptorsmentioning

confidence: 99%

“…A mutant lacking the nrfA gene showed a very increased sensitivity to nitrite Korte et al, 2015). NrfA is the periplasmic pentahaem cytochrome c nitrite reductase that performs the six-electron reduction of nitrite to ammonia (Einsle, 2011;Fritz et al, 2005;Liu & Peck, 1981;Romão et al, 2012;Simon, 2002). The catalytic site is an unusual lysine-bound high-spin haem where nitrite binds.…”

Section: Other Electron Acceptorsmentioning

confidence: 99%

A Post-Genomic View of the Ecophysiology, Catabolism and Biotechnological Relevance of Sulphate-Reducing Prokaryotes

Rabus

Venceslau

Wöhlbrand

et al. 2015

Advances in Microbial Physiology

265

286

View full text Add to dashboard Cite

“…An essential part of the dissimilatory process is the sixelectron, seven-proton reduction of nitrite to ammonia, which is efficiently accomplished without release of any intermediate. In this case it is called the respiratory nitrite ammonification process [2], and is catalyzed by CcNiR. Obviously, the effectiveness of the reduction critically depends on the electron and proton supply processes.…”

Section: Introductionmentioning

confidence: 99%

Reductive activation of the heme iron–nitrosyl intermediate in the reaction mechanism of cytochrome c nitrite reductase: a theoretical study

Bykov

Neese

2012

J Biol Inorg Chem

View full text Add to dashboard Cite

Cytochrome c nitrite reductase catalyzes the six-electron, seven-proton reduction of nitrite to ammonia without release of any detectable reaction intermediate. This implies a unique flexibility of the active site combined with a finely tuned proton and electron delivery system. In the present work, we employed density functional theory to study the recharging of the active site with protons and electrons through the series of reaction intermediates based on nitrogen monoxide [Fe(II)-NO(+), Fe(II)-NO·, Fe(II)-NO(-), and Fe(II)-HNO]. The activation barriers for the various proton and electron transfer steps were estimated in the framework of Marcus theory. Using the barriers obtained, we simulated the kinetics of the reduction process. We found that the complex recharging process can be accomplished in two possible ways: either through two consecutive proton-coupled electron transfers (PCETs) or in the form of three consecutive elementary steps involving reduction, PCET, and protonation. Kinetic simulations revealed the recharging through two PCETs to be a means of overcoming the predicted deep energetic minimum that is calculated to occur at the stage of the Fe(II)-NO· intermediate. The radical transfer role for the active-site Tyr(218), as proposed in the literature, cannot be confirmed on the basis of our calculations. The role of the highly conserved calcium located in the direct proximity of the active site in proton delivery has also been studied. It was found to play an important role in the substrate conversion through the facilitation of the proton transfer steps.

show abstract

Key Bacterial Multi-Centered Metal Enzymes Involved in Nitrate and Sulfate Respiration

Cited by 29 publications

References 144 publications

Crystal Structure of Adenylylsulfate Reductase fromDesulfovibrio gigasSuggests a Potential Self-Regulation Mechanism Involving the C Terminus of the β-Subunit

Crystal Structure of Adenylylsulfate Reductase fromDesulfovibrio gigasSuggests a Potential Self-Regulation Mechanism Involving the C Terminus of the β-Subunit

A Post-Genomic View of the Ecophysiology, Catabolism and Biotechnological Relevance of Sulphate-Reducing Prokaryotes

Reductive activation of the heme iron–nitrosyl intermediate in the reaction mechanism of cytochrome c nitrite reductase: a theoretical study

Contact Info

Product

Resources

About