Precise location of the Cu(II)-inhibitory binding site in higher plant and bacterial photosynthetic reaction centers as probed by light-induced absorption changes.

Yruela, Inmaculada; Alfonso, Miguel; Zarate, Iñaki Ortiz de; Montoya, Guillermo; Picorel, Rafael

doi:10.1016/s0021-9258(18)53906-5

Cited by 51 publications

(15 citation statements)

References 34 publications

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“…The fluorescence decay curves and the quantum yield given by Cu(II)-inhibited PSII centers were comparable with PSII centers in the "open" state, indicating that PSII particles treated with Cu(II) do still have an efficient charge separation. Our result is consistent with the work of Renger et al (1993) andSchro ¨der et al (1994) but is not in agreement with our earlier interpretation of an impaired charge separation up to Q A (Yruela et al, 1991(Yruela et al, , 1992(Yruela et al, , 1993 although it is still in agreement with our previous suggestion of an acceptor side effect of Cu(II) (Yruela et al, 1993).…”

Section: Discussionsupporting

confidence: 71%

“…Our previous investigations on the Cu(II)-inhibitory effect on the photosynthetic electron transport have been concentrated mainly on the characterization of the Cu(II)-binding site and the mechanism that regulates the Cu(II) inhibition in PSII (Yruela et al, 1991(Yruela et al, , 1992(Yruela et al, , 1993. We have suggested that Cu(II) affects the electron transport on the reducing side of PSII, close to the Pheo-Q A -Fe domain, the cofactors which are involved in the primary photochemical reactions of PSII.…”

Section: Discussionmentioning

confidence: 99%

“…Recently, we have made an extensive study on this subject and particularly on the Cu(II)-inhibitory effect (Yruela et al, 1991), its inhibitory mechanism (Yruela et al, 1992), and the location of the Cu(II)-binding site (Yruela et al, 1993). Our work suggested that Cu(II) impairs the photosynthetic electron transport on the acceptor side between Pheo and Q A and that Cu(II) would bind to an amino acid-(s) which is (are) necessary for the electron transport between † I.Y.…”

mentioning

confidence: 99%

“…* Author to whom correspondence should be addressed. Pheo and Q A (Yruela et al, 1993). However, despite all of these studies, the Cu(II)-inhibitory mechanism remains unclear, and the precise localization of the primary target of the Cu(II)-binding site is still a matter of debate.…”

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confidence: 99%

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Cu(II)-Inhibitory Effect on Photosystem II from Higher Plants. A Picosecond Time-Resolved Fluorescence Study

et al. 1996

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The influence of Cu(II) inhibition on the primary reactions of photosystem II (PSII) electron transport was studied by picosecond time-resolved fluorescence on isolated PSII membranes. The fluorescence decay from Cu(II)-inhibited PSII centers showed a dominant amplitude of a fast phase (100−300 ps) similar to PSII centers in the uninhibited “open state” and minor contributions of components around 600 ps and 2.6 ns. These data indicate efficient primary charge separation in PSII membranes incubated with Cu(II). The quantum yield of primary reactions in the inhibited PSII centers was similar to that of “open” PSII centers. Kinetic analysis of the decay curves in the framework of the exciton/radical pair equilibrium model showed no significant changes in the rate constants associated with the charge separation/recombination equilibrium. However, in closed centers (QA reduced), a decrease in the rate constant k 23, associated with the back-reaction of a relaxed radical pair, by a factor of 4 was calculated. The free energy losses upon primary charge separation (ΔG 1) and during subsequent radical pair relaxation (ΔG 2) were also determined in Cu(II)-inhibited centers and were compared with uninhibited centers. No changes in the ΔG 1 values and a significant decrease in the ΔG 2 values were found as compared with those of control PSII centers in the “closed” state. These data indicate that Cu(II) does not affect primary radical pair formation, but strongly affects the formation of a relaxed radical pair, by neutralizing the negative charge on QA - and eliminating the repulsive interaction between Pheo- and QA - and/or by modifying the general dielectric properties of the protein region, surrounding these cofactors. Moreover, a close attractive interaction between Pheo-, QA -, and Cu2+ can be proposed. Our results are in good agreement with very recent EPR results indicating an additional effect of Cu2+ on the acceptor side [Jegerschöld et al. (1995) Biochemistry 34, 12747−12758].

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Section: Discussionsupporting

confidence: 71%

Section: Discussionmentioning

confidence: 99%

mentioning

confidence: 99%

mentioning

confidence: 99%

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Cu(II)-Inhibitory Effect on Photosystem II from Higher Plants. A Picosecond Time-Resolved Fluorescence Study

et al. 1996

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“…From thermoluminescence and delayed luminescence studies, Mohanty et al (1989) proposed that the inhibition site is at the level of the secondary quinone acceptor (QB). Recently, based on spectrophotometric measurements of Qa and pheophytin reduction, Yruela et al (1991Yruela et al ( , 1992Yruela et al ( , 1993 challenged the earlier studies and suggested an inhibition site on the acceptor side of PS II in the pheophytin-Qa-non-heme Fe2+ region. However, these conclusions were disputed in recent optical studies (Schroder et al, 1994).…”

mentioning

confidence: 99%

Copper(II) Inhibition of Electron Transfer through Photosystem II Studied by EPR Spectroscopy

Jegerschöld¹,

Arellano²,

Schröder³

et al. 1995

Biochemistry

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EPR spectroscopy was applied to investigate the inhibition of electron transport in photosystem II by Cu2+ ions. Our results show that Cu2+ has inhibitory effects on both the donor and the acceptor side of photosystem II. In the presence of Cu2+, neither EPR signal IIvery fast nor signal IIfast, which both reflect oxidation of tyrosinez, could be induced by illumination. This shows that Cu2+ inhibits electron transfer from tyrosinez to the oxidized primary donor P680+. Instead of tyrosinez oxidation, illumination results in the formation of a new radical with g = 2.0028 +/- 0.0002 and a spectral width of 9.5 +/- 0.3 G. At room temperature, this radical amounts to one spin per PS II reaction center. Incubation of photosystem II membranes with cupric ions also results in release of the 16 kDa extrinsic subunit and conversion of cytochrome b559 to the low-potential form. On the acceptor side, QA can still be reduced by illumination or chemical reduction with dithionite. However, incubation with Cu2+ results in loss of the normal EPR signal from QA- which is coupled to the non-heme Fe2+ on the acceptor side (the QA(-)-Fe2+ EPR signal). Instead, reduction of QA results in the formation of a free radical spectrum which is 9.5 G wide and centered at g = 2.0044. This signal is attributed to QA- which is magnetically decoupled from the non-heme iron. This suggests that Cu2+ displaces the Fe2+ or severely alters its binding properties. The inhibition of tyrosinez is reversible upon removal of the copper ions with EDTA while the modification of QA was found to be irreversible.

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Development of flow cytometry‐based algal bioassays for assessing toxicity of copper in natural waters

Franklin

Stauber

Lim

2001

Enviro Toxic and Chemistry

160

105

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Copper toxicity to the freshwater algae Selenastrum capricornutum and Chlorella sp. and the marine algae Phaeodactylum tricornutum and Dunaliella tertiolecta was investigated using different parameters measured by flow cytometry: cell division rate inhibition, chlorophyll a fluorescence, cell size (i.e., light-scattering), and enzyme activity. These parameters were assessed regarding their usefulness as alternative endpoints for acute (1-24 h) and chronic (48-72 h) toxicity tests. At copper concentrations of 10 micrograms/L or less, significant inhibition (50%) of the cell division rate was observed after 48- and 72-h exposures for Chlorella sp., S. capricornutum, and P. tricornutum. Bioassays based on increases in algal cell size were also sensitive for Chlorella sp. and P. tricornutum. Copper caused both chlorophyll a fluorescence stimulation (48-h EC50 of 10 +/- 1 micrograms Cu/L for P. tricornutum) and inhibition (48-h EC50 of 14 +/- 6 micrograms Cu/L for S. capricornutum). For acute toxicity over short exposure periods, esterase activity in S. capricornutum using fluorescein diacetate offered a rapid alternative (3-h EC50 of 90 +/- 40 micrograms Cu/L) to growth inhibition tests for monitoring copper toxicity in mine-impacted waters. For all the effect parameters measured, D. tertiolecta was tolerant to copper at concentrations up to its solubility limit in seawater. These results demonstrate that flow cytometry is a useful technique for toxicity testing with microalgae and provide additional information regarding the general mode of action of copper (II) to algal species.

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Precise location of the Cu(II)-inhibitory binding site in higher plant and bacterial photosynthetic reaction centers as probed by light-induced absorption changes.

Cited by 51 publications

References 34 publications

Cu(II)-Inhibitory Effect on Photosystem II from Higher Plants. A Picosecond Time-Resolved Fluorescence Study

Cu(II)-Inhibitory Effect on Photosystem II from Higher Plants. A Picosecond Time-Resolved Fluorescence Study

Copper(II) Inhibition of Electron Transfer through Photosystem II Studied by EPR Spectroscopy

Development of flow cytometry‐based algal bioassays for assessing toxicity of copper in natural waters

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