Details

Autor(en) / Beteiligte

• Sheridan, Kevin J.
• Eaton-Rye, Julian J.
• Summerfield, Tina C.

Titel

Mutagenesis of Ile184 in the cd-loop of the photosystem II D1 protein modifies acceptor-side function via spontaneous mutation of D1-His252 in Synechocystis sp. PCC 6803

Ist Teil von

• Biochemical and biophysical research communications, 2024-04, Vol.702, p.149595, Article 149595

Ort / Verlag

United States: Elsevier Inc

Erscheinungsjahr

2024

Quelle

Access via ScienceDirect (Elsevier)

Beschreibungen/Notizen

• The Photosystem II water-plastoquinone oxidoreductase is a multi-subunit complex which catalyses the light-driven oxidation of water to molecular oxygen in oxygenic photosynthesis. The D1 reaction centre protein exists in multiple forms in cyanobacteria, including D1FR which is expressed under far-red light. We investigated the role of Phe184 that is found in the lumenal cd-loop of D1FR but is typically an isoleucine in other D1 isoforms. The I184F mutant in Synechocystis sp. PCC 6803 was similar to the control strain but accumulated a spontaneous mutation that introduced a Gln residue in place of His252 located on the opposite side of the thylakoid membrane. His252 participates in the protonation of the secondary plastoquinone electron acceptor QB. The I184F:H252Q double mutant exhibited reduced high-light-induced photodamage and an altered QB-binding site that impaired herbicide binding. Additionally, the H252Q mutant had a large increase in the variable fluorescence yield although the number of photochemically active PS II centres was unchanged. In the I184F:H252Q mutant the extent of the increased fluorescence yield decreased. Our data indicates substitution of Ile184 to Phe modulates PS II-specific variable fluorescence in cells with the His252 to Gln substitution by modifying the QB-binding site. •Ile184 in the lumenal cd-loop of D1 was changed to Phe found in far-red forms of D1.•Mutation of Ile184 led to a cytosolic His252 change to Gln and modified QB-binding.•His252 to Gln reduced ROS and herbicide binding, and increased PS II fluorescence.•The PS II variable fluorescence was attenuated in the I184F:H252Q double mutant.•Substitution at Ile184 in the cd-loop modifies the acceptor side of PS II at His252.