Probing tyrosine Z oxidation in photosystem II core complex isolated from spinach by EPR at liquid helium temperatures

Ren, Yanan; Zhang, Chunxi; Bao, Han; Shen, Jian‐Ren; Zhao, Jingquan

doi:10.1007/s11120-009-9410-x

Cited by 4 publications

(3 citation statements)

References 95 publications

(158 reference statements)

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“…The S 1 state PSII samples were prepared as described in Ref. [26]. The S 0 state PSII samples were prepared according to Ref.…”

Section: Methodsmentioning

confidence: 99%

“…The S 2 state samples were prepared as described in Ref. [26]: the S 1 state samples were treated with 10 min visible light illumination at 200 K followed by a 30 s dark-adaptation at 0ºC in the presence of 1 mmol/L DQ (Duroquinone). Finally, the samples were frozen, first in dry ice/ethanol (200 K), and then in liquid nitrogen (77 K).…”

Section: Methodsmentioning

confidence: 99%

“…Before EPR measurements, all samples were degassed with nitrogen gas at 200 K. Continuous visible light illumination at liquid helium temperatures (10 K) was carried out directly in the EPR cavity as described in Refs. [25,26]. EPR spectrometer settings were given in the figure legends.…”

Section: Methodsmentioning

confidence: 99%

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Methanol as a probe to investigate the relationship between the secondary electron donor TyrZ and the substrate water molecules in active photosystem II

et al. 2010

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The secondary electron donor, Tyr Z , is implicated in tuning the primary charge separation and the water oxidation in active photosystem II (PSII). Two types of mechanisms have been proposed to explain the function of Tyr Z . One is that Tyr Z tunes the water oxidation through the direct interaction with substrate water molecules; the other is that Tyr Z is located in a hydrophobic environment without interacting with H 2 O, and controls the water oxidation by tuning the strength of the hydrogen bond between Tyr Z and His190. Here, methanol was used as a probe to study the possible relationship between Tyr Z and H 2 O by monitoring the Tyr Z oxidation and Tyr Z • reduction at cryogenic temperatures with electron paramagnetic resonance spectroscopy. The oxidation of Tyr Z and reduction of Tyr Z • in both S 2 and S 0 states at 10 K were accelerated by addition of a small amount of methanol (6%).Theoretical studies indicate that Tyr oxidation becomes more difficult if it interacts directly with the methanol molecule; while the decrease of the polarity of its environment accelerates the oxidation of Tyr. Accordingly, CH 3 OH does not directly interact with Tyr Z in active PSII, and the accelerative effect of methanol is caused by the strength increase of the hydrogen bond between Tyr Z and His190, resulting from the decrease of polarity of their environment after the displacement of H 2 O by CH 3 OH inside PSII. Considering the similarity between methanol and water, the results in this study support the model in which Tyr Z does not interact with H 2 O in active PSII. photosystem II, secondary electron donor Tyr Z , methanol, water, electron paramagnetic resonance Citation: Bao H, Zhang C X, Ren Y N, et al. Methanol as a probe to investigate the relationship between the secondary electron donor Tyr Z and the substrate water molecules in active photosystem II.Photosystem II (PSII) is the unique biological system in nature to catalyze the oxidation of water to molecular oxygen by using sunlight [1,2]. The light excitation on the PSII reaction center induces the primary charge separation to form the high oxidizing species, P 680 +• , which drives the water catalytic oxidation at the Mn-cluster [3,4]. The turnover of the Mn-cluster leading to water oxidation involves five different states (S n , n=0−4) [5,6], in which S 0 is the initial state, S 1 is the dark stable state, and S 2 and S 3 are more oxidized states. D 1 -Tyr161 (Tyr Z ) is the secondary electron donor located between the Mn-cluster and P 680 . It forms a hydrogen bond with D 1 -His190. The oxidation of Tyr Z by P 680 +• is accompanied by the release of one proton to His190, thus forms a neutral radical, Tyr Z • [7]. Tyr Z plays crucial roles in tuning the primary charge separation in the reaction center and the water oxidation at Mn-cluster. Therefore, the properties and mechanisms of Tyr Z have been the topics under extensive studies [7]. However, due to its fast turnover and lack of characteristic electronic spectroscopic signatures in active PSII sampl...

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“…The S 1 state PSII samples were prepared as described in Ref. [26]. The S 0 state PSII samples were prepared according to Ref.…”

Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

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Methanol as a probe to investigate the relationship between the secondary electron donor TyrZ and the substrate water molecules in active photosystem II

et al. 2010

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Low-temperature electron transfer suggests two types of QA in intact photosystem II

Bao

Zhang

Ren

et al. 2010

Biochimica et Biophysica Acta (BBA) - Bioenergetics

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The correlation between the reduction of Q(A) and the oxidation of Tyr(Z) or Car/Chl(Z)/Cyt(b559) in spinach PSII enriched membranes induced by visible light at 10 K is studied by using electron paramagnetic resonance spectroscopy. Similar g=1.95-1.86 Q(A)(-*)EPR signals are observed in both Mn-depleted and intact samples, and both signals are long lived at low temperatures. The presence of PPBQ significantly diminished the light induced EPR signals from Q(A)(-*), Car(+*)/Chl(+*) and oxidized Cyt(b559), while enhancing the amplitude of the S(1)Tyr(Z)* EPR signal in the intact PSII sample. The quantification and stability of the g=1.95-1.86 EPR signal and signals arising from the oxidized Tyr(Z) and the side-path electron donors, respectively, indicate that the EPR-detectable g=1.95-1.86 Q(A)(-*) signal is only correlated to reaction centers undergoing oxidation of the side-path electron donors (Car/Chl(Z)/Cyt(b559)), but not of Tyr(Z). These results imply that two types of Q(A)(-*) probably exist in the intact PSII sample. The structural difference and possible function of the two types of Q(A) are discussed.

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Substitution of chloride by bromide modifies the low-temperature tyrosine Z oxidation in active photosystem II

Ren

Zhang

Zhao

2010

Biochimica et Biophysica Acta (BBA) - Bioenergetics

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Chloride is an essential cofactor for photosynthetic water oxidation. However, its location and functional roles in active photosystem II are still a matter of debate. We have investigated this issue by studying the effects of Cl- replacement by Br- in active PSII. In Br- substituted samples, Cl- is effectively replaced by Br- in the presence of 1.2 M NaBr under room light with protection of anaerobic atmosphere followed by dialysis. The following results have been obtained. i) The oxygen-evolving activities of the Br--PSII samples are significantly lower than that of the Cl--PSII samples; ii) The same S2 multiline EPR signals are observed in both Br- and Cl--PSII samples; iii) The amplitudes of the visible light induced S1TyrZ* and S2TyrZ* EPR signals are significantly decreased after Br- substitution; the S1TyrZ* EPR signal is up-shifted about 8G, whereas the S2TyrZ* signal is down-shifted about 12 G after Br- substitution. These results imply that the redox properties of TyrZ and spin interactions between TyrZ* and Mn-cluster could be significantly modified due to Br- substitution. It is suggested that Cl-/Br- probably coordinates to the Ca2+ ion of the Mn-cluster in active photosystem II.

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Probing tyrosine Z oxidation in photosystem II core complex isolated from spinach by EPR at liquid helium temperatures

Cited by 4 publications

References 95 publications

Methanol as a probe to investigate the relationship between the secondary electron donor TyrZ and the substrate water molecules in active photosystem II

Methanol as a probe to investigate the relationship between the secondary electron donor TyrZ and the substrate water molecules in active photosystem II

Low-temperature electron transfer suggests two types of QA in intact photosystem II

Substitution of chloride by bromide modifies the low-temperature tyrosine Z oxidation in active photosystem II

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