Remote Water‐Mediated Proton Transfer Triggers Inter‐Cu Electron Transfer: Nitrite Reduction Activation in Copper‐Containing Nitrite Reductase

ChemBioChem ◽  
2020 ◽  
Author(s):  
Xin Qin ◽  
Xiaohua Chen
Keyword(s):  
Electron Transfer ◽  
Proton Transfer ◽  
Nitrite Reductase ◽  
Nitrite Reduction

QM/MM MD simulations reveal an asynchronous PCET mechanism for nitrite reduction by copper nitrite reductase

2020 ◽  
Vol 22 (36) ◽  
pp. 20922-20928
Author(s):  
Ronny Cheng ◽  
Chun Wu ◽  
Zexing Cao ◽  
Binju Wang
Keyword(s):  
Electron Transfer ◽  
Proton Transfer ◽  
Nitrite Reductase ◽  
Md Simulations ◽  
Nitrite Reduction ◽  
Proton Coupled Electron Transfer

The nitrite reduction in copper nitrite reductase is found to proceed through an asynchronous proton-coupled electron transfer (PCET) mechanism, with electron transfer from T1-Cu to T2-Cu preceding the proton transfer from Asp98 to nitrite.

scholarly journals Redox-coupled proton transfer mechanism in nitrite reductase revealed by femtosecond crystallography

2016 ◽  
Vol 113 (11) ◽  
pp. 2928-2933 ◽  
Author(s):  
Yohta Fukuda ◽  
Ka Man Tse ◽  
Takanori Nakane ◽  
Toru Nakatsu ◽  
Mamoru Suzuki ◽  
...  
Keyword(s):  
Electron Transfer ◽  
Proton Transfer ◽  
Nitrite Reductase ◽  
Transient State ◽  
Carbonyl Oxygen ◽  
Nitrite Reduction ◽  
Hydroxyl Group ◽  
Intramolecular Electron Transfer ◽  
Metal Centers ◽  
Substrate Complex

Proton-coupled electron transfer (PCET), a ubiquitous phenomenon in biological systems, plays an essential role in copper nitrite reductase (CuNiR), the key metalloenzyme in microbial denitrification of the global nitrogen cycle. Analyses of the nitrite reduction mechanism in CuNiR with conventional synchrotron radiation crystallography (SRX) have been faced with difficulties, because X-ray photoreduction changes the native structures of metal centers and the enzyme–substrate complex. Using serial femtosecond crystallography (SFX), we determined the intact structures of CuNiR in the resting state and the nitrite complex (NC) state at 2.03- and 1.60-Å resolution, respectively. Furthermore, the SRX NC structure representing a transient state in the catalytic cycle was determined at 1.30-Å resolution. Comparison between SRX and SFX structures revealed that photoreduction changes the coordination manner of the substrate and that catalytically important His255 can switch hydrogen bond partners between the backbone carbonyl oxygen of nearby Glu279 and the side-chain hydroxyl group of Thr280. These findings, which SRX has failed to uncover, propose a redox-coupled proton switch for PCET. This concept can explain how proton transfer to the substrate is involved in intramolecular electron transfer and why substrate binding accelerates PCET. Our study demonstrates the potential of SFX as a powerful tool to study redox processes in metalloenzymes.

scholarly journals Nitrite reduction by copper through ligand-mediated proton and electron transfer

2015 ◽  
Vol 6 (6) ◽  
pp. 3373-3377 ◽  
Author(s):  
Cameron M. Moore ◽  
Nathaniel K. Szymczak
Keyword(s):  
Electron Transfer ◽  
Transfer Process ◽  
Copper Complex ◽  
Nitrite Reductase ◽  
Nitrite Reduction ◽  
Electron Transfer Process ◽  
Tripodal Ligand

A copper complex featuring a proton-responsive tripodal ligand reduces nitriteviaa proton/electron transfer process, which parallels copper nitrite reductase.

scholarly journals Electron transfer to nitrite reductase of Rhodobacter sphaeroides 2.4.3: examination of cytochromes c 2 and c Y

Microbiology ◽  
2006 ◽  
Vol 152 (5) ◽  
pp. 1479-1488 ◽  
Author(s):  
William P. Laratta ◽  
Michael J. Nanaszko ◽  
James P. Shapleigh
Keyword(s):  
Electron Transfer ◽  
Electron Donor ◽  
Rhodobacter Sphaeroides ◽  
Nitrite Reductase ◽  
Double Mutant ◽  
Reductase Activity ◽  
Nitrite Reduction ◽  
Nitrite Reductase Gene ◽  
Nitrite Reductase Activity

The role of cytochrome c 2, encoded by cycA, and cytochrome c Y, encoded by cycY, in electron transfer to the nitrite reductase of Rhodobacter sphaeroides 2.4.3 was investigated using both in vivo and in vitro approaches. Both cycA and cycY were isolated, sequenced and insertionally inactivated in strain 2.4.3. Deletion of either gene alone had no apparent effect on the ability of R. sphaeroides to reduce nitrite. In a cycA–cycY double mutant, nitrite reduction was largely inhibited. However, the expression of the nitrite reductase gene nirK from a heterologous promoter substantially restored nitrite reductase activity in the double mutant. Using purified protein, a turnover number of 5 s−1 was observed for the oxidation of cytochrome c 2 by nitrite reductase. In contrast, oxidation of c Y only resulted in a turnover of ∼0·1 s−1. The turnover experiments indicate that c 2 is a major electron donor to nitrite reductase but c Y is probably not. Taken together, these results suggest that there is likely an unidentified electron donor, in addition to c 2, that transfers electrons to nitrite reductase, and that the decreased nitrite reductase activity observed in the cycA–cycY double mutant probably results from a change in nirK expression.

ChemInform Abstract: Energy Transfer, Proton Transfer, and Electron Transfer Reactions Within Zeolites

ChemInform ◽  
2010 ◽  
Vol 30 (8) ◽  
pp. no-no
Author(s):  
V. Ramamurthy ◽  
P. Lakshminarasimhan ◽  
Clare P. Grey ◽  
Linda J. Johnston
Keyword(s):  
Electron Transfer ◽  
Energy Transfer ◽  
Proton Transfer ◽  
Transfer Reactions ◽  
Electron Transfer Reactions

scholarly journals Increased nitrite reductase activity of fetal versus adult ovine hemoglobin

2009 ◽  
Vol 296 (2) ◽  
pp. H237-H246 ◽  
Author(s):  
Arlin B. Blood ◽  
Mauro Tiso ◽  
Shilpa T. Verma ◽  
Jennifer Lo ◽  
Mahesh S. Joshi ◽  
...  
Keyword(s):  
Nitrite Reductase ◽  
Chronic Hypoxia ◽  
Reductase Activity ◽  
Fetal Hemoglobin ◽  
Nitrite Reduction ◽  
No Production ◽  
Low Oxygen ◽  
Nitrite Reductase Activity ◽  
Adult Hemoglobin ◽  
Severe Ischemia

Growing evidence indicates that nitrite, NO2−, serves as a circulating reservoir of nitric oxide (NO) bioactivity that is activated during physiological and pathological hypoxia. One of the intravascular mechanisms for nitrite conversion to NO is a chemical nitrite reductase activity of deoxyhemoglobin. The rate of NO production from this reaction is increased when hemoglobin is in the R conformation. Because the mammalian fetus exists in a low-oxygen environment compared with the adult and is exposed to episodes of severe ischemia during the normal birthing process, and because fetal hemoglobin assumes the R conformation more readily than adult hemoglobin, we hypothesized that nitrite reduction to NO may be enhanced in the fetal circulation. We found that the reaction was faster for fetal than maternal hemoglobin or blood and that the reactions were fastest at 50–80% oxygen saturation, consistent with an R-state catalysis that is predominant for fetal hemoglobin. Nitrite concentrations were similar in blood taken from chronically instrumented normoxic ewes and their fetuses but were elevated in response to chronic hypoxia. The findings suggest an augmented nitrite reductase activity of fetal hemoglobin and that the production of nitrite may participate in the regulation of vascular NO homeostasis in the fetus.

scholarly journals Why Orange Guaymas Basin Beggiatoa spp. Are Orange: Single-Filament-Genome-Enabled Identification of an Abundant Octaheme Cytochrome with Hydroxylamine Oxidase, Hydrazine Oxidase, and Nitrite Reductase Activities

2012 ◽  
Vol 79 (4) ◽  
pp. 1183-1190 ◽  
Author(s):  
Barbara J. MacGregor ◽  
Jennifer F. Biddle ◽  
Jason R. Siebert ◽  
Eric Staunton ◽  
Eric L. Hegg ◽  
...  
Keyword(s):  
Nitrite Reductase ◽  
Pure Culture ◽  
Gulf Of California ◽  
Microbial Mats ◽  
Physiological Role ◽  
Nitrite Reduction ◽  
Cold Seeps ◽  
Single Filament ◽  
Guaymas Basin ◽  
Content Type

ABSTRACTOrange, white, and yellow vacuolatedBeggiatoaceaefilaments are visually dominant members of microbial mats found near sea floor hydrothermal vents and cold seeps, with orange filaments typically concentrated toward the mat centers. No marine vacuolateBeggiatoaceaeare yet in pure culture, but evidence to date suggests they are nitrate-reducing, sulfide-oxidizing bacteria. The nearly complete genome sequence of a single orangeBeggiatoa(“CandidatusMaribeggiatoa”) filament from a microbial mat sample collected in 2008 at a hydrothermal site in Guaymas Basin (Gulf of California, Mexico) was recently obtained. From this sequence, the gene encoding an abundant soluble orange-pigmented protein in Guaymas Basin mat samples (collected in 2009) was identified by microcapillary reverse-phase high-performance liquid chromatography (HPLC) nano-electrospray tandem mass spectrometry (μLC–MS-MS) of a pigmented band excised from a denaturing polyacrylamide gel. The predicted protein sequence is related to a large group of octaheme cytochromes whose few characterized representatives are hydroxylamine or hydrazine oxidases. The protein was partially purified and shown byin vitroassays to have hydroxylamine oxidase, hydrazine oxidase, and nitrite reductase activities. From what is known ofBeggiatoaceaephysiology, nitrite reduction is the most likelyin vivorole of the octaheme protein, but future experiments are required to confirm this tentative conclusion. Thus, while present-day genomic and proteomic techniques have allowed precise identification of an abundant mat protein, and its potential activities could be assayed, proof of its physiological role remains elusive in the absence of a pure culture that can be genetically manipulated.

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