Phe265 of the D1 protein is required to stabilize plastoquinone binding in the QB-binding site of photosystem II in Synechocystis sp. PCC 6803
In Photosystem II electrons from water splitting pass through a primary quinone electron acceptor (Q<sub>A</sub>) to the secondary plastoquinone (Q<sub>B</sub>). The D2 protein forms the Q<sub>A</sub>-binding site and the D1 protein forms the Q<sub>B</sub>-binding site. A non-heme iron sits between Q<sub>A</sub> and Q<sub>B</sub> resulting in a quinone-Fe-acceptor complex that must be activated before assembly of the oxygen-evolving complex can occur. An extended loop (residues 223-266) between the fourth (helix D) and fifth (helix E) helices of the D1 protein activates forward electron transfer via a conformational change that stabilizes a bidentate bicarbonate ligand to the non-heme iron while simultaneously stabilizing the binding of Q<sub>B</sub>. We show that positioning of D1:Phe265 to provide a hydrogen bond to the distal oxygen of Q<sub>B</sub> is required for forward electron transfer. In addition, mutations targeting D1:Phe265, resulted in a 50 mV decrease in the Q<sub>B</sub>/Q<sub>B</sub><sup>-</sup> midpoint potential.
Authors
- Tina C. Summerfield (ORCID: https://orcid.org/0000-0003-1878-7019)
- Imre Vass (ORCID: https://orcid.org/0000-0003-4987-7842)
- Julian J. Eaton‐Rye (ORCID: https://orcid.org/0000-0003-4137-8838)
- Toby J Brown
Institutions
- HUN-REN Szegedi Biológiai Kutatóközpont (HU)
- Institute of Plant Biology (HU)
- University of Otago (NZ)
Publication Details
- Journal
- Biochemical and Biophysical Research Communications
- Published
- 2024-09-12
- DOI
- https://doi.org/10.1016/j.bbrc.2024.150692
- Citations
- 5
- Primary Topic
- Photosynthetic Processes and Mechanisms
- Type
- article
- Field-Weighted Citation Impact
- 1.17