Studies on the electron transfer from Tyr-161 of polypeptide D-1 to P680+ in PS II membrane fragments from spinach

Renger, G.; Hj, Eckert; Völker, M.

doi:10.1007/bf00048303

Cited by 30 publications

(18 citation statements)

References 49 publications

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“…Thus, in the Ca 2+ -depleted system the environment of Y Z may be structurally rather different relative to the native system where the distance between Y Z and the various components of the Mn cluster has been estimated as 8-20 Å (30, 109, 117). This suggestion is in line with the observed strong retardation of electron transfer between Y Z and P 680 + in Ca-depleted PSII (29,83,110). On the contrary, in Cl --depleted centers where electron transfer from Y Z to P 680 + occurs as fast as in controls, i.e., in nanoseconds (8), the difference spectrum Y Z ox -Y Z (8,111) is similar to the one measured in oxygen-evolving centers in the whole spectral region.…”

Section: Discussionsupporting

confidence: 86%

Tyrosine-Z in Oxygen-Evolving Photosystem II: A Hydrogen-Bonded Tyrosinate

1998

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In oxygen-evolving photosystem II (PSII), a tyrosine residue, D1Tyr161 (Y Z ), serves as the intermediate electron carrier between the catalytic Mn cluster and the photochemically active chlorophyll moiety P 680 . A more direct catalytic role of Y Z , as a hydrogen abstractor from bound water, has been postulated. That Y Z ox appears as a neutral (i.e. deprotonated) radical, Y Z • , in EPR studies is compatible with this notion. Data based on electrochromic absorption transients, however, are conflicting because they indicate that the phenolic proton remains on or near to Y Z ox . In Mn-depleted PSII the electron transfer between Y Z and P 680 + can be almost as fast as in oxygen-evolving material, however, only at alkaline pH. With an apparent pK of about 7 the fast reaction is suppressed and converted into an about 100-fold slower one which dominates at acid pH. In the present work we investigated the optical difference spectra attributable to the transition Y Z f Y Z ox as function of the pH. We scanned the UV and VIS range and used Mn-depleted PSII core particles and also oxygen-evolving ones. Comparing these spectra with published in vitro and in vivo spectra of phenolic compounds, we arrived at the following conclusions: In oxygen-evolving PSII Y Z resembles a hydrogen-bonded tyrosinate, Y Z (-) ‚‚‚H (+) ‚B. The phenolic proton is shifted toward a base B already in the reduced state and even more so in the oxidized state. The retention of the phenolic proton in a hydrogen-bonded network gives rise to a positive net charge in the immediate vicinity of the neutral radical Y Z • . It may be favorable both for the very rapid reduction by Y Z of P 680 + and for electron (not hydrogen) abstraction by Y Z • from the Mn-water cluster.Photosystem II (PSII) 1 produces molecular oxygen from water. It is located in photosynthetic membranes of plants and cyanobacteria. The inner core of PSII is a heterodimer of the D1D2 subunits which show homology with the L and M subunits of the purple bacterial RC (1). The primary electron donor of PSII, P 680 , is located close to the lumenal side of the membrane. The absorption of a quantum of light drives the charge separation between P 680 and the quinone acceptor at the stromal side (2). The very high redox potential of P 680 + drives water oxidation. It is a four-stepped process with at least four increasingly oxidized, metastable states S 0 to S 3 , plus a transient state S 4 that decays in milliseconds into S 0 under release of O 2 . P 680 + is reduced (in nanoseconds) by a redox-active tyrosine residue, Y Z (D1Tyr161 (3, 4)). Y Z ox is, in turn, reduced in microseconds by the oxygenevolving complex (OEC). The structure and exact location of the OEC is still ill-defined. It is formed by four manganese atoms (5, 6), possibly another redox cofactor, X (7-9), plus at least one Cl -ion (10) and one Ca 2+ (11, 12) ion. These cofactors serve various functions during water oxidation: The Mn cluster stores at least two of the oxidizing equivalents (namely on transitions S ...

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Section: Discussionsupporting

confidence: 86%

Tyrosine-Z in Oxygen-Evolving Photosystem II: A Hydrogen-Bonded Tyrosinate

1998

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“…An analysis of the 'fast' nanosecond kinetics within the framework of the Marcus theory [82] of nonadiabatic electron transfer (NET) led to a comparatively small reorganization energy of about 0.5 eV [83] and an edge-to-edge distance between Y Z and P680 of 9 AE 2 A [84], which is in perfect agreement with the XRDC data [48,59].…”

Section: Oxidation Of Y Z By P680 þ * and The Properties Of Y Dsupporting

confidence: 68%

“…Figure 21.6 shows a comparison of the Arrhenius plots and the H/D effects of the 'fast' nanosecond kinetics of PS II with an intact WOC and the dominating microsecond kinetics in samples deprived of the WOC. An evaluation of these data revealed that the reorganization energy of about 0.5 eV [83,100] increases by a factor of about 3 and reaches a value of 1.6 eV after destruction of the WOC [84,100,105]. The latter value closely resembles the number of 1.4 eV reported for model systems and Y Z oxidation by P680 þ * in Mn-depleted samples [77].…”

Section: Oxidation Of Y Z By P680 þ * and The Properties Of Y Dsupporting

confidence: 61%

“…This effect could also comprise a Ca 2þ release (for a discussion of this effect, see Ref. [72]), which is known to modulate the kinetics of reduction [83,112]. Interestingly, virtually the same pK a value ($ 4.7) was found for blockage of the lightinduced split signal [113], which is ascribed to the formation of S 1 Y ox Z at 5 K [91,[113][114][115].…”

Section: Oxidation Of Y Z By P680 þ * and The Properties Of Y Dmentioning

confidence: 51%

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Role of Hydrogen Bonds in Photosynthetic Water Splitting

Ренгер¹

2010

Hydrogen Bonding and Transfer in the Excited State

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“…This raises the question about the possibility of an allosteric effect of the Q B site on donor side reactions of PS II because all functional redox groups partici pating in water cleavage are currently assumed to be located in a heterodimer of polypeptides D 1 and D2 [2,3]. Our latest data indicate that at least in the case of D C M U the electron transfer rate from Tyr-161 of polypeptide D1 to P680+ re mains invariant to herbicide binding in the Q B site [34],…”

Section: Discussionmentioning

confidence: 89%

Studies on Herbicide Binding in Photosystem II Membrane Fragments from Spinach

Fromme¹,

Ренгер²

1990

Zeitschrift Für Naturforschung C

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Atrazine Binding, Photosystem II, Ca2+ Effects, Temperature Dependence, Mild ProteolysisThe mechanism of atrazine binding and its modification by Chelex-100-induced Ca2+ deple tion and proteolytic degradation by trypsin, was analyzed in PS II membrane fragments from spinach. It was found:1) Chelex-100 treatment leads in a comparatively slow process (/, 2 = 5 -10 min) to Ca2+ re moval from a site that is characterized by a high affinity as reflected by K u values of the order of 10 7 M. The number of these binding sites was found to be almost one per PS II in samples washed twice with Ca2+ -free buffer.2) Chelex-100 treatment does not affect the affinity of atrazine binding but increases the susceptibility to proteolytic attack by trypsin.3) The electron transport activity is only slightly affected by Chelex-100 treatment.4) The atrazine binding exhibits a rather small T-dependence within the physiological range of 7 °C to 27 °C.The implications of these findings for herbicide binding are discussed.

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Studies on the electron transfer from Tyr-161 of polypeptide D-1 to P680+ in PS II membrane fragments from spinach

Cited by 30 publications

References 49 publications

Tyrosine-Z in Oxygen-Evolving Photosystem II: A Hydrogen-Bonded Tyrosinate

Tyrosine-Z in Oxygen-Evolving Photosystem II: A Hydrogen-Bonded Tyrosinate

Role of Hydrogen Bonds in Photosynthetic Water Splitting

Studies on Herbicide Binding in Photosystem II Membrane Fragments from Spinach

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