Substrate water exchange in photosystem II core complexes of the extremophilic red alga Cyanidioschyzon merolae
2014 (English)In: Biochimica et Biophysica Acta - Bioenergetics, ISSN 0005-2728, E-ISSN 1879-2650, Vol. 1837, no 8, 1257-1262 p.Article in journal (Other academic) Published
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 S2and 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 ± 8 s− 1 and ks = 1.9 ± 0.3 s− 1 in the S2 state, and kf = 42 ± 2 s− 1 and kslow = 1.2 ± 0.3 s− 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.
Place, publisher, year, edition, pages
2014. Vol. 1837, no 8, 1257-1262 p.
Cyanidioschyzon merolae, photosystem II, Water oxidation, oxygen evolution, substrate–water exchange, membrane-inlet mass spectrometry
Chemical Engineering Biochemistry and Molecular Biology
IdentifiersURN: urn:nbn:se:umu:diva-86497DOI: 10.1016/j.bbabio.2014.04.001ISI: 000339133800004OAI: oai:DiVA.org:umu-86497DiVA: diva2:699572
This paper is dedicated to the memory of Warwick Hillier (18.10.1967-10.01.2014). Using membrane-inlet mass spectrometry and FTIR spectroscopy Warwick made many important discoveries regarding substrate-water binding to the OEC and the mechanism of water-oxidation. He was a very good scientist and friend that was highly appreciated throughout the photosynthesis community. In 2007 he was awarded the Robin-Hill award of the International Society for Photosynthesis Research (ISPR).2014-02-272014-02-272014-09-01Bibliographically approved