Substrate water exchange in photosystem II core complexes of the extremophilic red alga Cyanidioschyzon merolae

Substrate water exchange in photosystem II core complexes of the extremophilic red alga Cyanidioschyzon merolae. Nilsson, H., Krupnik, T., Kargul, J., & Messinger, J. Biochimica et Biophysica Acta (BBA) - Bioenergetics, 1837(8):1257–1262, August, 2014.

Paper doi abstract bibtex

The binding affinity of the two substrate–water molecules to the water-oxidizing Mn4CaO5 catalyst in photosystem II core complexes of the extremophilic red alga Cyanidioschyzon merolae was studied in the S2 and S3 states by the exchange of bound 16O-substrate against 18O-labeled water. The rate of this exchange was detected via the membrane-inlet mass spectrometric analysis of flash-induced oxygen evolution. For both redox states a fast and slow phase of water-exchange was resolved at the mixed labeled m/z 34 mass peak: kf=52±8s−1 and ks=1.9±0.3s−1 in the S2 state, and kf=42±2s−1 and kslow=1.2±0.3s−1 in S3, respectively. Overall these exchange rates are similar to those observed previously with preparations of other organisms. The most remarkable finding is a significantly slower exchange at the fast substrate–water site in the S2 state, which confirms beyond doubt that both substrate–water molecules are already bound in the S2 state. This leads to a very small change of the affinity for both the fast and the slowly exchanging substrates during the S2→S3 transition. Implications for recent models for water-oxidation are briefly discussed.

@article{nilsson_substrate_2014,
	title = {Substrate water exchange in photosystem {II} core complexes of the extremophilic red alga \textit{{Cyanidioschyzon} merolae}},
	volume = {1837},
	issn = {0005-2728},
	url = {https://www.sciencedirect.com/science/article/pii/S0005272814001078},
	doi = {10.1016/j.bbabio.2014.04.001},
	abstract = {The binding affinity of the two substrate–water molecules to the water-oxidizing Mn4CaO5 catalyst in photosystem II core complexes of the extremophilic red alga Cyanidioschyzon merolae was studied in the S2 and S3 states by the exchange of bound 16O-substrate against 18O-labeled water. The rate of this exchange was detected via the membrane-inlet mass spectrometric analysis of flash-induced oxygen evolution. For both redox states a fast and slow phase of water-exchange was resolved at the mixed labeled m/z 34 mass peak: kf=52±8s−1 and ks=1.9±0.3s−1 in the S2 state, and kf=42±2s−1 and kslow=1.2±0.3s−1 in S3, respectively. Overall these exchange rates are similar to those observed previously with preparations of other organisms. The most remarkable finding is a significantly slower exchange at the fast substrate–water site in the S2 state, which confirms beyond doubt that both substrate–water molecules are already bound in the S2 state. This leads to a very small change of the affinity for both the fast and the slowly exchanging substrates during the S2→S3 transition. Implications for recent models for water-oxidation are briefly discussed.},
	number = {8},
	urldate = {2024-12-10},
	journal = {Biochimica et Biophysica Acta (BBA) - Bioenergetics},
	author = {Nilsson, Håkan and Krupnik, Tomasz and Kargul, Joanna and Messinger, Johannes},
	month = aug,
	year = {2014},
	keywords = {Membrane-inlet mass spectrometry, Oxygen evolution, Photosystem II, Substrate–water exchange, Water oxidation},
	pages = {1257--1262},
}

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