Binding of the inhibitor NH3 to the oxygen-evolving apparatus of spinach chloroplasts

Velthuys, B.R.

doi:10.1016/0005-2728(75)90145-0

Cited by 73 publications

(52 citation statements)

References 18 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Loss of the extrinsic polypeptides (psbQ and psbP), as documented here, increases the rate of chloride exchange (34), so we conducted our experiments with a high buffer chloride concentration. NH 3 has been proposed to bind to the OEC in the S 2 and S 3 states, but not in the S 1 state (11,35). It has been suggested previously that ammonia free base binds directly to Mn (10,11,36,37).…”

Section: Discussionmentioning

confidence: 99%

A hydrogen-bonding network plays a catalytic role in photosynthetic oxygen evolution

Polander

Barry

2012

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

111

View full text Add to dashboard Cite

In photosystem II, oxygen evolution occurs by the accumulation of photo-induced oxidizing equivalents at the oxygen-evolving complex (OEC). The sequentially oxidized states are called the S 0 -S 4 states, and the dark stable state is S 1 . Hydrogen bonds to water form a network around the OEC; this network is predicted to involve multiple peptide carbonyl groups. In this work, we tested the idea that a network of hydrogen bonded water molecules plays a catalytic role in water oxidation. As probes, we used OEC peptide carbonyl frequencies, the substrate-based inhibitor, ammonia, and the sugar, trehalose. Reaction-induced FT-IR spectroscopy was used to describe the protein dynamics associated with the S 1 to S 2 transition. A shift in an amide CO vibrational frequency (1664 (S 1 ) to 1653 (S 2 ) cm −1 ) was observed, consistent with an increase in hydrogen bond strength when the OEC is oxidized. Treatment with ammonia/ammonium altered these CO vibrational frequencies. The ammonia-induced spectral changes are attributed to alterations in hydrogen bonding, when ammonia/ammonium is incorporated into the OEC hydrogen bond network. The ammonia-induced changes in CO frequency were reversed or blocked when trehalose was substituted for sucrose. This trehalose effect is attributed to a displacement of ammonia molecules from the hydrogen bond network. These results imply that ammonia, and by extension water, participate in a catalytically essential hydrogen bond network, which involves OEC peptide CO groups. Comparison to the ammonia transporter, AmtB, reveals structural similarities with the bound water network in the OEC.amide carbonyl frequency | Amt B transporter | photosystem II | vibrational spectroscopy | water oxidation I n oxygenic photosynthesis, photosystem II (PSII) catalyzes the oxidation of water and reduction of plastoquinone (1). Each reaction center includes the transmembrane subunits D1, D2, CP43, and CP47, which bind the redox-active cofactors. After photoexcitation, a charge separation is generated between the dimeric chl donor, P 680 , and a bound plastoquinone, Q A . Q A − reduces a second quinone, Q B , and P 680 þ oxidizes a tyrosine residue, YZ, Y161 in the D1 polypeptide. The radical, YZ•, is a powerful oxidant (2). Under physiological conditions, YZ• oxidizes the Mn 4 CaO 5 cluster, where water oxidation occurs (3). Four sequential photooxidations lead to the release of molecular oxygen (4). The oxygen yield fluctuates with period four. The sequentially oxidized states of the Mn cluster are called the Sn states, where n refers to the number of oxidizing equivalents stored at the OEC. S 1 is the dark stable state of the OEC. A single flash given to a dark-adapted sample of PSII generates the S 2 state, which corresponds to the oxidation of Mn(III) to Mn (IV) (5). The water oxidation chemistry in the S state cycle occurs on the microsecond to millisecond time scale, and oxygen is released during the S 3 to S 0 transition (4, 6).The structure of PSII has been reported at a resolution of 1.9 Å (3). T...

show abstract

Section: Discussionmentioning

confidence: 99%

A hydrogen-bonding network plays a catalytic role in photosynthetic oxygen evolution

Polander

Barry

2012

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

111

View full text Add to dashboard Cite

show abstract

“…If our hypothesis, that ammonia inhibition is equivalent to chloride depletion, is correct, then it might be expected that S-state behavior in ammonia-poisoned and chloride-depleted thylakoid membranes would be similar. In fact, it has been observed in independent investigations [4,7] that the SZ and S3 states have enhanced lifetimes in both ammonia-poisoned and chloride-depleted preparations. Our hypothesis would also predict that under appropriate conditions, low-temperature EPR signals ascribed to the Sz state [14] might exhibit hyperfine structure arising from an interaction with the chloride nucleus (I= 3/2).…”

Section: Discussionmentioning

confidence: 99%

The mechanism of amine inhibition of the photosynthetic oxygen evolving complex

1983

View full text Add to dashboard Cite

Amines inhibit photosynthetic oxygen evolution by binding to manganese in the oxygen evolving complex. This inhibition is more effective if chloride is absent. Steady-state kinetic analyses show that ammonia and chloride compete for the same site in the oxygen evolving complex; inhibition of oxygen evolution by either chloride depletion or by ammonia addition induces Signal IIr, which saturates at high microwave power. These data indicate that chloride is bound at the manganese site in the oxygen evolving complex. We propose that the anion functions as a bridging ligand mediating electron transfer between manganese atoms and perhaps also between manganese and Z, the primary donor to P680. Photosystem II Oxygen evolution Bridging ligand Amine inhibition Signal IIfChloride

show abstract

“…states but not to the SI state, and also that the redox potentials of the S2 and S3 states are altered by NH3 (Velthuys, 1975). Later it was found that weak binding of NH3 to the S1 state also occurs, although only to a small extent compared with binding to the S2 state (Andr6asson et al, 1988).…”

Section: Summary and Model For The Mn Tetramermentioning

confidence: 99%

X-ray absorption spectroscopy and EPR studies of oriented spinach thylakoid preparations

Andrews

1995

View full text Add to dashboard Cite

In this study, oriented Photosystem 11 (PS n) particles from spinach chloroplasts are studied with electron paramagnetic resonance (EPR) and x-ray absorption spectroscopy VAS) to determine more details of the structure of the oxygen evolving complex (OEC).The nature of halide binding to Mn is also studied with C1 K-edge and Mn EXAFS (extended x-ray absorption fine structure) of Mn-C1 model compounds, and with Mn EXAFS of oriented PS 1T in which Br has replaced C1.In chapter 2, oriented PS 11 particles from spinach were studied with EPR spectroscopy. The mosaic spread for these samples was determined by comparison of the oxidized cytochrome b559 (cyt b559+) signal measured at angles of 0" to 360" between the EPR magnetic field and sample membrane normal with simulations of oriented cyt b559+.The tyrosine YD+ signal was measured for these oriented samples at 0" and 90°, and a linear relationship was found between the dichroism found in the tyrosine YD+ signal and the mosaic spread.In chapters 3 and 4, Mn XAS was performed on oriented PS 11 membrane particles isolated from spinach. These studies were on control samples (chapter 3) and on samples treated with ammonia (chapter 4), a water analog which can yield insight into the binding of water by the OEC. Structural features of the tetranuclear Mn cluster and the orientation of the cluster with respect to the lipid bilayer were determined in the S2 state of the Kok cycle 1 for control samples, and on the annealed S2 state for the ammonia-treated samples.Variation of the sample orientation with respect to the x-ray e-vector yields highly dichroic In chapter 5, the binding of halide to Mn was studied using C1 K-edge XAS and Mn EXAFS on Mn-CI model compounds, and Mn EXAFS on oriented Br-treated PS IL From the C1 K-edges of model compounds, direct ligation of C1 to Mn could be confirmed with the presence of a pre-edge feature: 'a forbidden 1s to 3d transition which is seen due to mixing of Mn 3d orbitals with C13p orbitals. Bridging and terminal C1 bonds to Mn could be distinguish& EXAFS of Mn-C1 model compounds revealed that Mn-C1 interactions, especially bridging interactions, make an important contribution to the EXAFS. EXAFS of oriented Br-treated PS 11 showed differences from EXAFS of control CI-treated PS II that were on the same order as the variation from sample to sample. Fits to Br-treated and Cl control samples were also inconclusive. Thus, it is not possible to 9 establish or rule out direct ligation of C1 to Mn in the OEC with these studies.2

show abstract

Binding of the inhibitor NH3 to the oxygen-evolving apparatus of spinach chloroplasts

Cited by 73 publications

References 18 publications

A hydrogen-bonding network plays a catalytic role in photosynthetic oxygen evolution

A hydrogen-bonding network plays a catalytic role in photosynthetic oxygen evolution

The mechanism of amine inhibition of the photosynthetic oxygen evolving complex

X-ray absorption spectroscopy and EPR studies of oriented spinach thylakoid preparations

Contact Info

Product

Resources

About