The low spin - high spin equilibrium in the S-2-state of the water oxidizing enzyme

Date

2018-05-01

Author

Boussac, Alain
Ugur, Ilke
Marıon, Antoıne
Sugiura, Miwa
Kaila, Ville R. I.
Rutherford, A. William

Metadata

Show full item record

This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.

Item Usage Stats

211
views

0
downloads

In Photosystem II (PSII), the Mn4CaO5-cluster of the active site advances through five sequential oxidation states (S-0 to S-4) before water is oxidized and O-2 is generated. Here, we have studied the transition between the low spin (LS) and high spin (HS) configurations of S-2 using EPR spectroscopy, quantum chemical calculations using Density Functional Theory (DFT), and time-resolved UV-visible absorption spectroscopy. The EPR experiments show that the equilibrium between S-2(LS) and S-2(HS) is pH dependent, with a pK(a) approximate to 8.3 (n approximate to 4) for the native Mn4CaO5 and 7.5 (n = 1) for Mn4SrO5. The DFT results suggest that exchanging Ca with Sr modifies the electronic structure of several titratable groups within the active site, including groups that are not direct ligands to Ca/Sr, e.g., W1/W2, Asp61, His332 and His337. This is consistent with the complex modification of the pK(a) upon the Ca/Sr exchange. EPR also showed that NH3 addition reversed the effect of high pH, NH3-S2LS being present at all pH values studied. Absorption spectroscopy indicates that NH3 is no longer bound in the S(3)Tyr(z) state, consistent with EPR data showing minor or no NH3-induced modification of S-3 and S-0. In both Ca-PSII and Sr-PSII, S-2(HS) was capable of advancing to S-3 at low temperature (198 K). This is an experimental demonstration that the S-2(LS) is formed first and advances to S-3 via the S-2(HS) state without detectable intermediates. We discuss the nature of the changes occurring in the S-2(LS) to S-2(HS) transition which allow the S-2(HS) to S-3 transition to occur below 200 K. This work also provides a protocol for generating S-3 in concentrated samples without the need for saturating flashes.

Subject Keywords

Biophysics, Cell Biology, Biochemistry

URI

https://hdl.handle.net/11511/41581

Journal

BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS

DOI

https://doi.org/10.1016/j.bbabio.2018.02.010

Collections

Department of Chemistry, Article

Suggestions

OpenMETU
Core

The effect of cysteine-43 mutation on thermostability and kinetic properties of citrate synthase from Thermoplasma acidophilum Kocabıyık, Semra; Russel, RJM; Danson, MJ; Hough, DW (Elsevier BV, 1996-07-05) In this study, we have substituted serine-43 by cysteine in the recombinant citrate synthase from a moderately thermophilic Archaeon Thermoplasma acidophilum, for site-specific attachment of labels and have investigated the effects of this mutation on the biochemical properties and thermal stability of the enzyme. Both wild-type and the mutant enzymes were purified to homogenity using affinity chromatography on Matrex Gel Red A. The mutant Thermoplasma citrate synthase is very similar to wild-type citrate s...
The effect of valine substitution for glycine in the dimer interface of citrate synthase from Thermoplasma acidophilum on stability and activity Kocabıyık, Semra (Elsevier BV, 2000-08-28) To determine the role of hydrophobic interactions in the dimer interface of citrate synthase (CS) from Thermoplasma (Tp) acidophilum in thermostabilization, we have used site-directed mutagenesis to replace Gly 196 by Val on the helix L of the subunit interface. Recombinant wild-type and Gly 196 mutant TpCS enzymes were largely identical in terms of substrate specificities (K-m for oxaloacetate and acetyl CoA). However, the mutation not only reduced catalytic activity (about 10-fold) (i.e., V-max, K-cat and...
Vitamin E Decreases the Order of the Phospholipid Model Membranes in the Gel Phase: An FTIR Study Severcan, Feride (Portland Press Ltd., 1997-4-1) The effect of α-tocopherol on the frequency of the CH2 stretching bands of infrared spectra of dipalmitoylphosphotidylcholine multibilayers has been investigated, both in H2O and 2H2O buffer, to determine the reason for the discrepancy in the literature between the results of different spectroscopic techniques relating to the effect of α-tocopherol on membrane order in the gel phase. In contrast to previous FTIR studies, the present FTIR results indicate that αT increases the frequencies of the CH2 stretchi...
Investigating the active centre of the Scytalidium thermophilum catalase YÜZÜGÜLLÜ, YONCA; Trinh, Chi H.; Fairhurst, Lucy; Ögel, Zümrüt Begüm; McPherson, Michael J.; Pearson, Arwen R. (International Union of Crystallography (IUCr), 2013-04-01) Almost all monofunctional haem catalases contain a highly conserved core containing the active site, which is connected to the exterior of the enzyme by three channels. These channels have been identified as potential routes for substrate flow and product release. To further investigate the role of these molecular channels, a series of mutants of Scytalidium thermophilum catalase were generated. The three-dimensional structures of four catalase variants, N155A, V123A, V123C and V123T, have been determined a...
Effect of progesterone on DPPC membrane: Evidence for lateral phase separation and inverse action in lipid dynamics Korkmaz, F; Severcan, Feride (Elsevier BV, 2005-08-15) Interactions of progesterone with zwitterionic dipalmitoyl phosphatidylcholine (DPPC) triultilamellar liposomes were investigated as a function of temperature and progesterone concentration by using three non-invasive techniques namely Fourier transform infrared spectroscopy, turbidity at 440 nm, and differential scanning calorimetry. The results reveal that progesterone changes the physical properties of DPPC bilayers by decreasing the main phase-transition temperature, abolishing the pre-transition, broad...

Citation Formats

A. Boussac, I. Ugur, A. Marıon, M. Sugiura, V. R. I. Kaila, and A. W. Rutherford, “The low spin - high spin equilibrium in the S-2-state of the water oxidizing enzyme,” BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS, pp. 342–356, 2018, Accessed: 00, 2020. [Online]. Available: https://hdl.handle.net/11511/41581.