Size-distributions of antenna and acceptor-pool of Photosystem II

Hemelrijk, Petra W.; Gorkom, Hans J. van

doi:10.1016/0005-2728(96)00006-0

Cited by 12 publications

(8 citation statements)

References 31 publications

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“…On earlier occasions, precise simulations of S-state turnover in a flash series have been obtained by assuming a reversible temporary inactivation of the S 3 state (41,43). On the basis of the present data, it seems likely that the Cl -concentration in those measurements was near or below the K d in the S 3 state and the model used here would fully account for those data.…”

Section: Discussionsupporting

confidence: 55%

S-State Dependence of Chloride Binding Affinities and Exchange Dynamics in the Intact and Polypeptide-Depleted O₂ Evolving Complex of Photosystem II

Wincencjusz

1998

Biochemistry

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The Clbinding properties in the successive oxidation states of the O 2 evolving complex of photosystem II were investigated by measurements of UV absorbance changes, induced by a series of saturating flashes, that monitor manganese oxidation state transitions. In dark-adapted, intact photosystem II, Clcan be replaced by NO 3in minutes, in an exchange reaction that depends on the NO 3concentration and that is not rate-limited by dissociation of Clfrom its binding site. Preillumination of dark-adapted photosystem II by one or two flashes accelerated the NO 3substitution reaction by an order of magnitude. A quantitative analysis of the Clconcentration dependence of UV absorbance changes, measured in photosystem II preparations depleted of extrinsic 17 and 23 kDa polypeptides, shows that the Clbinding properties of photosystem II change with the oxidation state of the oxygen evolving complex. Although the affinity for the individual S-states could not be determined with precision, it is shown that the affinity is an order of magnitude lower in the S 2 state than in the S 1 state. Comparison of the results obtained using intact photosystem II and preparations depleted of the 17 and 23 kDa extrinsic polypeptides suggests that these proteins constitute a diffusion barrier, which prevents fast equilibration of the Clbinding site with the medium, but does not change the Claffinity of the binding site.

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Section: Discussionsupporting

confidence: 55%

S-State Dependence of Chloride Binding Affinities and Exchange Dynamics in the Intact and Polypeptide-Depleted O₂ Evolving Complex of Photosystem II

Wincencjusz

1998

Biochemistry

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“…The latter discrepancy could be quantified in first approximation by determination of the best-fitting miss probability if the period four oscillation was simulated by a simple Kok scheme with S-state independent misses, plus a small average EL increase per flash. This description is too simple to allow a good fit [as reported before (24)], but it showed that the average miss probability was between 5% and 8%, much lower than the 17.5% found when the EL oscillation with CCCP was simulated with a two-state model (solid lines in Figure 1).…”

Section: Resultsmentioning

confidence: 88%

“…The maximum fluorescence, reached at about 50 µs after the flash, shows a period four oscillation with a flash number similar to those in refs 25-27, attributed to an S-state dependent amount of long-lived P 680 + , which is a strong fluorescence quencher. The overall rise of the fluorescence yield with flash number results from depletion of the plastoquinone pool and could be completely prevented by the addition of 25 µM artificial electron acceptor 2,5-dichloro-p-benzoquinone (not shown, but see ref 24). When the ADRY agents FCCP (Figure 2B) or CCCP (Figure 2C) were added in sufficient amounts to suppress the period four oscillation, also the overall rise with flash number disappeared.…”

Section: Resultsmentioning

confidence: 96%

Kinetics of Electron Transfer from Q_A to Q_B in Photosystem II

2001

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The oxidation kinetics of the reduced photosystem II electron acceptor Q(A)(-) was investigated by measurement of the chlorophyll fluorescence yield transients on illumination of dark-adapted spinach chloroplasts by a series of saturating flashes. Q(A)(-) oxidation depends on the occupancy of the "Q(B) binding site", where this reaction reduces plastoquinone to plastoquinol in two successive photoreactions. The intermediate, one-electron-reduced plastosemiquinone anion Q(B)(-) remains tightly bound, and its reduction by Q(A)(-) may proceed with simple first-order kinetics. The next photoreaction, in contrast, may find the Q(B) binding site occupied by a plastoquinone, a plastoquinol, or neither of the two, resulting in heterogeneous Q(A)(-) oxidation kinetics. The assumption of monophasic Q(B)(-) reduction kinetics is shown to allow unambiguous decomposition of the observed multiphasic Q(A)(-) oxidation. At pH 6.5 the time constant for Q(A)(-) oxidation was found to be 0.2-0.4 ms with Q(B) in the site, 0.6-0.8 ms with Q(B)(-) in the site, 2-3 ms when the site is empty and Q(B) has to bind first, and of the order of 0.1 s if the site is temporarily blocked by the presence of Q(B)H(2) or other low-affinity inhibitors such as carbonyl cyanide m-chlorophenylhydrazone (CCCP). Effects of pH and H(2)O/D(2)O exchange were found to be remarkably nonspecific. No influence of the S-states could be demonstrated.

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“…When the cyt b 6 f complex was inhibited by a saturating concentration of DBMIB ( Figure 2C), the number of oxidizing equivalents in the PQ pool after dark incubation was about 2 PQ/PS2 for cells grown photoautotrophically. This corresponds to about 80% pool reduction, assuming 10 PQ/PS2 (published data indicate about 8 ( 2 PQ/PS2 for cyanobacteria (14,26,54) and 9 ( 3 for higher plants (55)(56)(57)(58)(59)(60)(61)(62)). A similar value of 3 oxidizing equivalents per PS2 was found for Synechococcus sp.…”

Section: Discussionmentioning

confidence: 97%

Electron Transport Routes in Whole Cells ofSynechocystissp. Strain PCC 6803: The Role of the Cytochromebd-Type Oxidase

et al. 2002

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The plastoquinone pool is the central switching point of both respiratory and photosynthetic electron transport in cyanobacteria. Its redox state can be monitored noninvasively in whole cells using chlorophyll fluorescence induction, avoiding possible artifacts associated with thylakoid membrane preparations. This method was applied to cells of Synechocystis sp. PCC 6803 to study respiratory reactions involving the plastoquinone pool. The role of the respiratory oxidases known from the genomic sequence of Synechocystis sp. PCC 6803 was investigated by a combined strategy using inhibitors and deletion strains that lack one or more of these oxidases. The putative quinol oxidase of the cytochrome bd-type was shown to participate in electron transport in thylakoid membranes. The activity of this enzyme in thylakoids was strongly dependent on culture conditions; it was increased under conditions where the activity of the cytochrome b(6)f complex alone may be insufficient for preventing over-reduction of the PQ pool. In contrast, no indication of quinol oxidase activity in thylakoids was found for a second alternative oxidase encoded by the ctaII genes.

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Size-distributions of antenna and acceptor-pool of Photosystem II

Cited by 12 publications

References 31 publications

S-State Dependence of Chloride Binding Affinities and Exchange Dynamics in the Intact and Polypeptide-Depleted O₂ Evolving Complex of Photosystem II

S-State Dependence of Chloride Binding Affinities and Exchange Dynamics in the Intact and Polypeptide-Depleted O₂ Evolving Complex of Photosystem II

Kinetics of Electron Transfer from Q_A to Q_B in Photosystem II

Electron Transport Routes in Whole Cells ofSynechocystissp. Strain PCC 6803: The Role of the Cytochromebd-Type Oxidase

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Size-distributions of antenna and acceptor-pool of Photosystem II

Cited by 12 publications

References 31 publications

S-State Dependence of Chloride Binding Affinities and Exchange Dynamics in the Intact and Polypeptide-Depleted O2 Evolving Complex of Photosystem II

S-State Dependence of Chloride Binding Affinities and Exchange Dynamics in the Intact and Polypeptide-Depleted O2 Evolving Complex of Photosystem II

Kinetics of Electron Transfer from QA to QB in Photosystem II

Electron Transport Routes in Whole Cells ofSynechocystissp. Strain PCC 6803: The Role of the Cytochromebd-Type Oxidase

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S-State Dependence of Chloride Binding Affinities and Exchange Dynamics in the Intact and Polypeptide-Depleted O₂ Evolving Complex of Photosystem II

S-State Dependence of Chloride Binding Affinities and Exchange Dynamics in the Intact and Polypeptide-Depleted O₂ Evolving Complex of Photosystem II

Kinetics of Electron Transfer from Q_A to Q_B in Photosystem II