scholarly journals Visualizing the protons in a metalloenzyme electron proton transfer pathway

2020 ◽  
Vol 117 (12) ◽  
pp. 6484-6490 ◽  
Author(s):  
Hanna Kwon ◽  
Jaswir Basran ◽  
Juliette M. Devos ◽  
Reynier Suardíaz ◽  
Marc W. van der Kamp ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Electron Transfer ◽  
Hydrogen Bonding ◽  
Proton Transfer ◽  
Proton Donor ◽  
Biological Processes ◽  
Proton Coupled Electron Transfer ◽  
Neutron Structure ◽  
Bona Fide ◽  
Electron Proton Transfer

In redox metalloenzymes, the process of electron transfer often involves the concerted movement of a proton. These processes are referred to as proton-coupled electron transfer, and they underpin a wide variety of biological processes, including respiration, energy conversion, photosynthesis, and metalloenzyme catalysis. The mechanisms of proton delivery are incompletely understood, in part due to an absence of information on exact proton locations and hydrogen bonding structures in a bona fide metalloenzyme proton pathway. Here, we present a 2.1-Å neutron crystal structure of the complex formed between a redox metalloenzyme (ascorbate peroxidase) and its reducing substrate (ascorbate). In the neutron structure of the complex, the protonation states of the electron/proton donor (ascorbate) and all of the residues involved in the electron/proton transfer pathway are directly observed. This information sheds light on possible proton movements during heme-catalyzed oxygen activation, as well as on ascorbate oxidation.

scholarly journals Deciphering the incognito role of water in a light driven proton coupled electron transfer process

2018 ◽  
Vol 9 (4) ◽  
pp. 910-921 ◽  
Author(s):  
Senthil Kumar Thiyagarajan ◽  
Raghupathy Suresh ◽  
Vadivel Ramanan ◽  
Perumal Ramamurthy
Keyword(s):  
Electron Transfer ◽  
Proton Transfer ◽  
Transfer Process ◽  
Electron Transfer Process ◽  
Solvent Water ◽  
Proton Coupled Electron Transfer ◽  
Electron Proton Transfer ◽  
Role Of Solvent ◽  
Proton Transfer Process

The incognito role of solvent water as a proton transfer bridge in a multi-site electron proton transfer process was depicted.

scholarly journals Crystal structure and hydrogen bonding in the water-stabilized proton-transfer salt brucinium 4-aminophenylarsonate tetrahydrate

2016 ◽  
Vol 72 (5) ◽  
pp. 751-755 ◽  
Author(s):  
Graham Smith ◽  
Urs D. Wermuth
Keyword(s):  
Crystal Structure ◽  
Hydrogen Bond ◽  
Hydrogen Bonding ◽  
Hydrogen Bonds ◽  
Proton Transfer ◽  
Network Structure ◽  
Three Dimensional ◽  
Water Molecules ◽  
Arsanilic Acid ◽  
Dimensional Network

In the structure of the brucinium salt of 4-aminophenylarsonic acid (p-arsanilic acid), systematically 2,3-dimethoxy-10-oxostrychnidinium 4-aminophenylarsonate tetrahydrate, (C23H27N2O4)[As(C6H7N)O2(OH)]·4H2O, the brucinium cations form the characteristic undulating and overlapping head-to-tail layered brucine substructures packed along [010]. The arsanilate anions and the water molecules of solvation are accommodated between the layers and are linked to them through a primary cation N—H...O(anion) hydrogen bond, as well as through water O—H...O hydrogen bonds to brucinium and arsanilate ions as well as bridging water O-atom acceptors, giving an overall three-dimensional network structure.

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 Hydrogen bonding between hydroxylic donors and MLCT-excited Ru(bpy)2(bpz)2+ complex: implications for photoinduced electron–proton transfer

2019 ◽  
Vol 55 (42) ◽  
pp. 5870-5873 ◽  
Author(s):  
Sergei V. Lymar ◽  
Gerald F. Manbeck ◽  
Dmitry E. Polyansky
Keyword(s):  
Free Energy ◽  
Hydrogen Bonding ◽  
Proton Transfer ◽  
Energy Correlation ◽  
Electron Proton Transfer

Rates of electron–proton transfer within the H-bonded exciplexes are evaluated using the free energy correlation with donor's H-bonding acidity.

scholarly journals Atomically manipulated proton transfer energizes water oxidation on silicon carbide photoanodes

2018 ◽  
Vol 6 (47) ◽  
pp. 24358-24366 ◽  
Author(s):  
Hao Li ◽  
Huan Shang ◽  
Yuchen Shi ◽  
Rositsa Yakimova ◽  
Mikael Syväjärvi ◽  
...  
Keyword(s):  
Silicon Carbide ◽  
Electron Transfer ◽  
Proton Transfer ◽  
Water Oxidation ◽  
Proton Coupled Electron Transfer ◽  
Rate Limiting Step ◽  
Limiting Step ◽  
Rate Limiting

Preferential exposure of Si-face of SiC will mechanistically shift the rate limiting step of water oxidation from sluggish proton-coupled electron transfer on C-face to a more energy-favorable electron transfer.

Proton transfer in bacterial nitric oxide reductase

2006 ◽  
Vol 34 (1) ◽  
pp. 188-190 ◽  
Author(s):  
U. Flock ◽  
J. Reimann ◽  
P. Ädelroth
Keyword(s):  
Nitric Oxide ◽  
Proton Transfer ◽  
Structural Model ◽  
No Reduction ◽  
Paracoccus Denitrificans ◽  
Proton Donor ◽  
Nitric Oxide Reductase ◽  
Reduction Of No ◽  
Proton Coupled Electron Transfer ◽  
Electron Reduction

The NOR (nitric oxide reductase) from Paracoccus denitrificans catalyses the two-electron reduction of NO to N2O (2NO+2H++2e−→N2O+H2O). The NOR is a divergent member of the superfamily of haem-copper oxidases, oxygen-reducing enzymes which couple the reduction of oxygen with translocation of protons across the membrane. In contrast, reduction of NO catalysed by NOR is non-electrogenic which, since electrons are supplied from the periplasmic side of the membrane, implies that the protons needed for NO reduction are also taken from the periplasm. Thus NOR must contain a proton-transfer pathway leading from the periplasmic side of the membrane into the catalytic site. The proton pathway has not been identified, and the mechanism and timing of proton transfer during NO reduction is unknown. To address these questions, we have studied the reaction between NOR and the chemically less reactive oxidant O2 [Flock, Watmough and Ädelroth (2005) Biochemistry 44, 10711–10719]. When fully reduced NOR reacts with O2, proton-coupled electron transfer occurs in a reaction that is rate-limited by internal proton transfer from a group with a pKa of 6.6. This group is presumably an amino acid residue close to the active site that acts as a proton donor also during NO reduction. The results are discussed in the framework of a structural model that identifies possible candidates for the proton donor as well as for the proton-transfer pathway.

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