Probing the role of Valine 185 of the D1 protein in the Photosystem II oxygen evolution

Miwa Sugiura , Tania Tibiletti , Itsuki Takachi , Yuya Hara , Shin Kanawaku , Julien Selles , Alain Boussac (1, 2)

1 I2BC - Institut de Biologie Intégrative de la Cellule
2 PS2 - Photosystème II

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. The V185 of the D1 protein has been shown to be an important amino acid in PSII function (Dilbeck et al. Biochemistry 52 (2013) 6824-6833). Here, we have studied its role by making a V185T site-directed mutant in the thermophilic cyanobacterium Thermosynechococcus elongatus. The properties of the V185T-PSII have been compared to those of the WT*3-PSII by using EPR spectroscopy, polarography, thermoluminescence and time-resolved UV-visible absorption spectroscopy. It is shown that the V185 and the chloride binding site very likely interact via the H-bond network linking Tyr(z) and the halide. The V185 contributes to the stabilization of S-2 into the low spin (LS), S = 1/2, configuration. Indeed, in the V185T mutant a high proportion of S-2 exhibits a high spin (HS), S = 5/2, configuration. By using bromocresol purple as a dye, a proton release was detected in the S(1)Tyr(Z)center dot -\textgreater S(2)(LS)Tyr(Z) transition in the V185T mutant in contrast to the WT*3-PSII in which there is no proton release in this transition. Instead, in WT*3-PSII, a proton release kinetically much faster than the S(2)(LS)Tyr(z)center dot -\textgreater S(3)Tyr(Z) transition was observed and we propose that it occurs in the S(2)(LS)Tyr(Z)center dot -\textgreater S(2)(HS)Tyr(Z). intermediate step before the S(2)(HS)Tyr(Z)center dot -\textgreater S(3)Tyr(Z) transition occurs. The dramatic slowdown of the S(3)Tyr(Z)center dot -\textgreater S(0)Tyr(Z) transition in the V185T mutant does not originate from a structural modification of the Mn4CaO5 cluster since the spin S = 3 S-3 EPR signal is not modified in the mutant. More probably, it is indicative of the strong implication of V185 in the tuning of an efficient relaxation processes of the H-bond network and/or of the protein.

Mots clés: Photosystem II; Oxygen evolution; Spin state; charge recombination; Mn4CaO5 cluster; alternating electron; dioxygen formation; electron-paramagnetic-res; epr signals; evolving mn4cao5 cluster; ftir difference spectroscopy; photosynthetic water oxidation; proton release; thermosynechococcus-elongatus

Domaines: Sciences du Vivant [q-bio]

Miwa Sugiura, Tania Tibiletti, Itsuki Takachi, Yuya Hara, Shin Kanawaku, et al.. Probing the role of Valine 185 of the D1 protein in the Photosystem II oxygen evolution. Biochimica biophysica acta (BBA) - Bioenergetics, 2018, 1859 (12), pp.1259--1273. ⟨10.1016/j.bbabio.2018.10.003⟩. ⟨hal-02294879⟩