The Iron-Quinone Acceptor Complex

Petrouleas, Vasili; Crofts, Antony R.

doi:10.1007/1-4020-4254-x_9

Cited by 80 publications

(113 citation statements)

References 192 publications

Supporting

Mentioning

109

Contrasting

Order By: Relevance

“…P680 is composed of four chlorophyll a (Chla) molecules, P D1 /P D2 , Chl D1 /Chl D2 , and two pheophytin a molecules (Pheo D1 /Pheo D2 , D1-His215, donates an H-bond to the Q B carbonyl O atom that is nearer to the Fe complex (O QB( proximal) ) (figure 7). The Q B carbonyl O atom distal to the Fe complex (O QB(distal) ) accepts an H-bond from D1-Ser264, which itself accepts an H-bond from D1-His252 (figure 7), which is located on the protein surface in contact with the aqueous medium [1,[70][71][72][73]. It is known that Q B † 2 formation is linked to proton uptake [74,75], and comparisons with the structure of the bacterial reaction centre led to the first suggestion that the D1-His252 was the residue undergoing protonation in response to Q B † 2 formation [76].…”

Section: How Does the Short H-bond Appear In Ftir Studies?mentioning

confidence: 99%

Proton transfer reactions and hydrogen-bond networks in protein environments

Ishikita

Saito

2014

J. R. Soc. Interface.

177

169

View full text Add to dashboard Cite

In protein environments, proton transfer reactions occur along polar or charged residues and isolated water molecules. These species consist of H-bond networks that serve as proton transfer pathways; therefore, thorough understanding of H-bond energetics is essential when investigating proton transfer reactions in protein environments. When the pK a values (or proton affinity) of the H-bond donor and acceptor moieties are equal, significantly short, symmetric H-bonds can be formed between the two, and proton transfer reactions can occur in an efficient manner. However, such short, symmetric H-bonds are not necessarily stable when they are situated near the protein bulk surface, because the condition of matching pK a values is opposite to that required for the formation of strong salt bridges, which play a key role in protein-protein interactions. To satisfy the pK a matching condition and allow for proton transfer reactions, proteins often adjust the pK a via electron transfer reactions or H-bond pattern changes. In particular, when a symmetric H-bond is formed near the protein bulk surface as a result of one of these phenomena, its instability often results in breakage, leading to large changes in protein conformation.

show abstract

Section: How Does the Short H-bond Appear In Ftir Studies?mentioning

confidence: 99%

Proton transfer reactions and hydrogen-bond networks in protein environments

Ishikita

Saito

2014

J. R. Soc. Interface.

177

169

View full text Add to dashboard Cite

show abstract

“…In addition to these His ligands, other two His residues, D1-His272 and D2-His268, and a bicarbonate ion function as ligands to the non-heme iron [18,21,63]. Under physiological conditions, the non-heme iron is not involved in the electron transfer reaction from Q A to Q B [16,38,48], because of its high E m value of about +400 mV at pH 7.0 with a pH dependence of −60 mV/pH [8,25,44,49]. However, under oxidative conditions, e.g., in the presence of ferricyanide, the non-heme iron is oxidized to Fe 3+ and serves as an endogenous electron acceptor, and hence Fe 3+ is re-reduced to Fe 2+ by light illumination.…”

Section: Ftir Spectroelectrochemical Study On the Non-heme Ironmentioning

confidence: 99%

“…The main reason for this is the difficulty in spectroscopic detection of the Q B reaction. It is well known that fluorescence measurement is useful to monitor the redox states of Q A because reduction of Q A increases the level of fluorescence [9,33,47,48]. However, the fluorescence method is not applicable to the Q B reaction.…”

Section: Ftir Spectroelectrochemical Study On Q Bmentioning

confidence: 99%

“…In photosystem II, light absorption triggers charge separation between the chlorophyll dimer (P680) and the pheophytin (Pheo) electron acceptor to produce P680 + Pheo − [51]. On the electron-acceptor side, an electron on Pheo − is transferred to the primary quionone electron acceptor (Q A ) and then to the secondary quinone electron acceptor (Q B ) [16,38,48], while on the electron donor side, the electron hole on P680…”

Section: Introductionmentioning

confidence: 99%

“…[18,21,63]. In spite of the same chemical species and similar molecular interactions, Q A and Q B have rather different functions [16,38,48]; Q A performs only a single-electron reaction and relays an electron from Pheo − to Q B , whereas Q B can be doubly reduced to become plastoquinole (PQH 2 ) by binding two protons and leaves the binding site of PSII.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

FTIR spectroelectrochemistry combined with a light-induced difference technique: Application to the iron-quinone electron acceptor in photosystem II

Kato

Noguchi

2016

BSI

View full text Add to dashboard Cite

Abstract. Photosystem II (PSII) in plants and cyanobacteria performs light-driven water oxidation to obtain electrons necessary for CO 2 fixation. In PSII, a series of electron transfer reactions take place from the Mn 4 CaO 5 cluster, the catalytic site of water oxidation, to a plastoquinone molecule via several redox cofactors. Light-induced Fourier transform infrared (FTIR) difference spectroscopy has been extensively used to investigate the structures and reactions of the redox cofactors in PSII. Recently, FTIR spectroelectrochemistry combined with the light-induced difference technique was applied to study the mechanism of electrontransfer regulation in PSII involving the quinone electron acceptors, Q A and Q B , and the non-heme iron that bridges them. In this mini-review, this combined FTIR method is introduced, and obtained results about the redox reactions of the non-heme iron and Q B , involving the long-range interaction of the Mn 4 CaO 5 cluster with the electron-acceptor side, are summarized.

show abstract

The D1:Ser268 residue of Photosystem II contributes to an alternative pathway for Q_B protonation in the absence of bound bicarbonate

Forsman

Eaton‐Rye

2020

FEBS Letters

View full text Add to dashboard Cite

Photosystem II catalyses the splitting of water and the reduction in plastoquinone in thylakoid membranes of all oxygenic photosynthetic organisms. The final step in quinol formation is protonation of the reduced secondary quinone electron acceptor normalQnormalB2‐false(H+false)to give QBH2. The proton for this step is hypothesized to be provided by a hydrogen‐bond network incorporating amino acids from the Photosystem II D1 and D2 reaction center proteins, together with several bound waters and a bicarbonate ion ligated to a non‐heme iron found between the primary plastoquinone electron acceptor QA and QB. The aim of this study was to investigate the role of bicarbonate and the D1:Ser268 residue in the formation of QBH2. Using targeted mutagenesis of the D1 protein in the cyanobacterium Synechocystis sp. PCC 6803, we have created two mutants, S268A and S268T. Our D1:Ser268 mutants exhibited increased sensitivity to formate‐induced inhibition of electron transfer between QA and QB and indicate that D1:Ser268 and bicarbonate support the second protonation in the formation of QBH2 via two different pathways that both lead to the protonation of normalQnormalB2‐false(H+false) by D1:His215.

show abstract

The Iron-Quinone Acceptor Complex

Cited by 80 publications

References 192 publications

Proton transfer reactions and hydrogen-bond networks in protein environments

Proton transfer reactions and hydrogen-bond networks in protein environments

FTIR spectroelectrochemistry combined with a light-induced difference technique: Application to the iron-quinone electron acceptor in photosystem II

The D1:Ser268 residue of Photosystem II contributes to an alternative pathway for Q_B protonation in the absence of bound bicarbonate

Contact Info

Product

Resources

About

The Iron-Quinone Acceptor Complex

Cited by 80 publications

References 192 publications

Proton transfer reactions and hydrogen-bond networks in protein environments

Proton transfer reactions and hydrogen-bond networks in protein environments

FTIR spectroelectrochemistry combined with a light-induced difference technique: Application to the iron-quinone electron acceptor in photosystem II

The D1:Ser268 residue of Photosystem II contributes to an alternative pathway for QB protonation in the absence of bound bicarbonate

Contact Info

Product

Resources

About

The D1:Ser268 residue of Photosystem II contributes to an alternative pathway for Q_B protonation in the absence of bound bicarbonate