Phe265 of the D1 protein is required to stabilize plastoquinone binding in the QB-binding site of photosystem II in Synechocystis sp. PCC 6803
Year: 2024
Type: article
Abstract: In Photosystem II electrons from water splitting pass through a primary quinone electron acceptor (Q A ) to the secondary plastoquinone (Q B ). The D2 protein forms the Q A -binding site and the D1 protein forms the Q B -binding site. A non-heme iron sits between Q A and Q B 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 B . We show that positioning of D1:Phe265 to provide a hydrogen bond to the distal oxygen of Q B is required for forward electron transfer. In addition, mutations targeting D1:Phe265, resulted in a 50 mV decrease in the Q B /Q B – midpoint potential. • Photosystem II (PS II) has two plastoquinone electron acceptors Q A and Q B . • A conformational change of the DE-Loop of the D1 protein enables Q B to bind. • Mutations at Phe265 do not disrupt PS II assembly but slow electron transfer to Q B . • Phe265 tunes the redox midpoint potential of the Q B /Q B – couple. • The aromaticity of Phe265 of the DE-loop is required for Q B binding.
Language: English
Subfield: Molecular Biology
Domain: Life Sciences
Open Access status: hybrid
Estimated APC paid: $2,880
Funders: University of Otago, ONGC Energy Centre
Awards: G1982903219, G5432704244
OpenAlex ID: W4402496331