Evidence from directed mutagenesis that aspartate 170 of the D1 polypeptide influences the assembly and/or stability of the manganese cluster in the photosynthetic water-splitting complex

Boerner, Renee J.; Nguyen, Anh P.; Barry, Bridgette A.; Debus, Richard J.

doi:10.1021/bi00144a005

Cited by 121 publications

(151 citation statements)

References 82 publications

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“…DCMU is an inhibitor that will block electron transfer to Q B (20) (Fig. 1 A, reaction 3) and cause transfer of any electrons on Q B back to Q A (21). This reequilibration, coupled with multiple flash illuminations, will result in a majority of closed centers containing Q A Ϫ in the dark, which cannot undergo a stable P 680 ϩ Q A Ϫ charge separation.…”

Section: Resultsmentioning

confidence: 99%

Time-resolved vibrational spectroscopy detects protein-based intermediates in the photosynthetic oxygen-evolving cycle

Barry

Cooper²,

Riso³

et al. 2006

Proc. Natl. Acad. Sci. U.S.A.

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Photosynthetic oxygen production by photosystem II (PSII) is responsible for the maintenance of aerobic life on earth. The production of oxygen occurs at the PSII oxygen-evolving complex (OEC), which contains a tetranuclear manganese (Mn) cluster. Photo-induced electron transfer events in the reaction center lead to the accumulation of oxidizing equivalents on the OEC. Four sequential photooxidation reactions are required for oxygen production. The oxidizing complex cycles among five oxidation states, called the S n states, where n refers to the number of oxidizing equivalents stored. Oxygen release occurs during the S 3-to-S0 transition from an unstable intermediate, known as the S4 state. In this report, we present data providing evidence for the production of an intermediate during each S state transition. These proteinderived intermediates are produced on the microsecond to millisecond time scale and are detected by time-resolved vibrational spectroscopy on the microsecond time scale. Our results suggest that a protein-derived conformational change or proton transfer reaction precedes Mn redox reactions during the S 2-to-S3 and S 3-to-S0 transitions.manganese cluster ͉ photosynthesis ͉ photosystem II ͉ time-resolved IR ͉ water oxidation T ime-resolved vibrational spectroscopy can detect chemical intermediates formed during enzymatic catalysis. Advantages include the technique's exquisite structural sensitivity and its high temporal resolution. Recent advances in methodology and interpretation have produced insights into the catalytic mechanism in several biological systems (for examples, see refs. 1-4).In this paper, we report the use of time-resolved IR spectroscopy to investigate the mechanism of photosynthetic water oxidation. Photosystem II (PSII) catalyzes the oxidation of water and the reduction of bound plastoquinone. Photoexcitation of PSII leads to the oxidation of the chlorophyll donor, P 680 , and the sequential reduction of a pheophytin (Fig. 1A, reaction 1) and a plastoquinone, Q A ( Fig. 1 A, reaction 2), in picoseconds. Q A reduces Q B to generate a semiquinone radical, Q B Ϫ , on the microsecond time scale (Fig. 1 A, reaction 3 ) (reviewed in ref. 5).A second photoexcitation leads to the reduction and protonation of Q B Ϫ to form the quinol Q B H 2 . The rate of reduction of Q B is faster than the rate of reduction of Q B Ϫ (see ref. 6 and references therein), which gives rise to a characteristic period-2 oscillation in kinetics originating on the PSII acceptor side (7).The primary chlorophyll donor, P 680 , oxidizes a tyrosine, Y Z (Y161 in the D1 subunit), on the nanosecond to microsecond time scale (Fig. 1 A, reaction 4). In turn, tyrosine Y Z ⅐ oxidizes the oxygen-evolving complex (OEC) on every flash (Fig. 1 A, reaction 5) (8). Four sequential photooxidation reactions are required for oxygen production, and the oxidizing complex cycles among five oxidation states, called the S n states, where n refers to the number of oxidizing equivalents stored (9). The rate of OEC oxidation slows as o...

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Section: Resultsmentioning

confidence: 99%

Time-resolved vibrational spectroscopy detects protein-based intermediates in the photosynthetic oxygen-evolving cycle

Barry

Cooper²,

Riso³

et al. 2006

Proc. Natl. Acad. Sci. U.S.A.

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“…This property has been previously used to monitor the integrity of the high affinity manganese binding site in various D1 mutants (9,27,28). Fig.…”

Section: Resultsmentioning

confidence: 99%

Evidence that D1 Processing Is Required for Manganese Binding and Extrinsic Protein Assembly into Photosystem II

Roose¹,

Pakrasi

2004

Journal of Biological Chemistry

106

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Photosystem II (PSII) is a large membrane protein complex that catalyzes oxidation of water to molecular oxygen. During its normal function, PSII is damaged and frequently turned over. The maturation of the D1 protein, a key component in PSII, is a critical step in PSII biogenesis. The precursor form of D1 (pD1) contains a C-terminal extension, which is removed by the protease CtpA to yield PSII complexes with oxygen evolution activity. To determine the temporal position of D1 processing in the PSII assembly pathway, PSII complexes containing only pD1 were isolated from a CtpAdeficient strain of the cyanobacterium Synechocystis 6803. Although membranes from the mutant cell had nearly 50% manganese, no manganese was detected in isolated ⌬ctpAHT3 PSII, indicating a severely decreased manganese affinity. However, chlorophyll fluorescence decay kinetics after a single saturating flash suggested that the donor Y Z was accessible to exogenous Mn 2؉ ions. Furthermore, the extrinsic proteins PsbO, PsbU, and PsbV were not present in PSII isolated from this mutant. However, PsbO and PsbV were present in mutant membranes, but the amount of PsbV protein was consistently less in the mutant membranes compared with the control membranes. We conclude that D1 processing precedes manganese binding and assembly of the extrinsic proteins into PSII. Interestingly, the Psb27 protein was found to be more abundant in ⌬ctpAHT3 PSII than in HT3 PSII, suggesting a possible role of Psb27 as an assembly factor during PSII biogenesis.Photosystem II (PSII), 1 a multisubunit protein complex localized to the thylakoid membranes of cyanobacteria and chloroplasts, performs a light-driven electron transfer from water to plastoquinones, generating molecular oxygen as a byproduct (1). Cyanobacterial PSII consists of more than 20 subunits including both membrane-integral and extrinsically associated proteins (2, 3). In addition to its protein components, PSII also has many associated cofactors including chlorophylls, pheophytins, plastoquinones, manganese, non-heme iron, calcium, and chloride atoms as well as two heme groups (2, 3). Recent structural studies (4 -6) have greatly advanced our knowledge of the arrangement of the components within the functional complex. In particular, new details on the structure of the tetra-manganese-calcium cluster of the oxygen-evolving complex have given key insights into the mechanism of the water oxidation reaction (6).Despite these advances, these static structures are not adequate to understand the dynamic nature of the assembly and turn-over of the PSII complex. The structural complexity of PSII requires precise and regulated assembly, yet the PSII biogenesis pathway is poorly understood and many questions still remain as to how the components are assembled into a functional PSII complex. Furthermore, PSII assembly occurs frequently, because the PSII complex is rapidly turned over even under normal conditions (7). As a consequence of the electron transfer reactions, the D1 protein is irreversibly damaged, remo...

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“…PSII preparations from Synechocystis sp. PCC 6803 typically have a small amount of contamination from PSI (4,16,26,36). The PSII preparations employed here had =10% contamination.…”

Section: Methodsmentioning

confidence: 94%

A difference Fourier-transform infrared study of two redox-active tyrosine residues in photosystem II.

MacDonald

Bixby

Barry

1993

Proc. Natl. Acad. Sci. U.S.A.

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Photosystem II, the photosynthetic wateroxidizing complex, contains two redox-active tyrosine residues.Although current models suggest that these tyrosines are located in symmetric positions in the reaction center, there are functional differences between them. To elucidate those structural factors that give rise to this functional asymmetry, we have used difference Fourier-transform infrared spectroscopy to obtain the vibrational difference spectrum associated with the oxidation of each of these redox-active residues. Isotopic labeling was employed to definitively assign vibrational lines to the redox-active tyrosines. This work has shown that the vibrational spectra of the two redox-active species are significantly different from each other. This result suggests that the structure of the redox-active residue helps to determine its role in electron transfer in the reaction center.Photosystem II (PSII) is the photosynthetic membrane complex that carries out the light-induced oxidation of water and reduction of plastoquinone in plants, green algae, and prokaryotic cyanobacteria. Isotopic labeling and electron paramagnetic resonance (EPR) spectroscopy have been used to show that PSII contains two redox-active tyrosine residues (1, 2). One of these tyrosines, Z, is involved in electron transfer between the primary chlorophyll donor, P680, and the manganese-containing catalytic site (for review, see ref.3). The other tyrosine, D, is not directly involved in the electron-transfer events that lead to oxygen evolution; the function of D is not known (4). These tyrosines are believed to be symmetrically located in the reaction center (5-8).The oxidized forms of D and Z, D-and Z-, are neutral radicals that give rise to characteristic and similar EPR signals (1, 2). These EPR signals have been used to show that D and Z have different oxidation and reduction kinetics. Z is oxidized by P680+ (9), and Z-is, in turn, reduced by the manganese cluster (10, 11). If the metal cluster is removed, the reduction of Z-is slowed to the millisecond time regime (12)(13)(14). On the other hand, D is usually oxidized by the manganese cluster with a 1-sec rise time (15). In the absence of a functional manganese cluster, D can be oxidized by P680+ (16, 17). The decay time of D-is on the order of several hours (18).In addition to the kinetic differences described above, there are other functional differences between the Z and D tyrosines. For example, the redox potential of D has been measured to be 0.76 V (19), whereas the potential of Z has been estimated to be about 1 V (20). Further, the two radicals show different accessibility to exogenous reductants (21).This functional asymmetry may be due to differences in the structure of the two redox-active residues. The EPR spectra of Z-and D-do not give detailed insight into this question. Since these radicals are immobilized, their EPR lineshapes are broadened by anisotropic interactions, and small structural alterations would not be readily observable. Recently,The publication costs o...

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Evidence from directed mutagenesis that aspartate 170 of the D1 polypeptide influences the assembly and/or stability of the manganese cluster in the photosynthetic water-splitting complex

Cited by 121 publications

References 82 publications

Time-resolved vibrational spectroscopy detects protein-based intermediates in the photosynthetic oxygen-evolving cycle

Time-resolved vibrational spectroscopy detects protein-based intermediates in the photosynthetic oxygen-evolving cycle

Evidence that D1 Processing Is Required for Manganese Binding and Extrinsic Protein Assembly into Photosystem II

A difference Fourier-transform infrared study of two redox-active tyrosine residues in photosystem II.

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