7ZXY

3.15 Angstrom cryo-EM structure of the dimeric cytochrome b6f complex from Synechocystis sp. PCC 6803 with natively bound plastoquinone and lipid molecules.

Summary for 7ZXY

• Entry DOI: 10.2210/pdb7zxy/pdb
• EMDB information: 15017
• Descriptor: Cytochrome b6, PROTOPORPHYRIN IX CONTAINING FE, HEME C, ... (15 entities in total)
• Functional Keywords: cytochrome bc complexes, electron transfer, cytochrome b6f, photosynthesis, cyanobacteria, oxidoreductase
• Biological source: Synechocystis sp. PCC 6803; More
• Total number of polymer chains: 16
• Total formula weight: 227290.28

Authors

Malone, L.A.,Procter, M.S.,Farmer, D.F.,Swainsbury, D.J.K.,Hawkings, F.R.,Pastorelli, F.,Emrich-Mills, T.Z.,Siebert, A.,Hunter, C.N.,Hitchcock, A.,Johnson, M.P. (deposition date: 2022-05-23, release date: 2022-07-06, Last modification date: 2024-11-06)

Primary citation

Proctor, M.S.,Malone, L.A.,Farmer, D.A.,Swainsbury, D.J.K.,Hawkings, F.R.,Pastorelli, F.,Emrich-Mills, T.Z.,Siebert, C.A.,Hunter, C.N.,Johnson, M.P.,Hitchcock, A.
Cryo-EM structures of the Synechocystis sp. PCC 6803 cytochrome b6f complex with and without the regulatory PetP subunit.
Biochem.J., 479:1487-1503, 2022

PubMed Abstract: In oxygenic photosynthesis, the cytochrome b6f (cytb6f) complex links the linear electron transfer (LET) reactions occurring at photosystems I and II and generates a transmembrane proton gradient via the Q-cycle. In addition to this central role in LET, cytb6f also participates in a range of processes including cyclic electron transfer (CET), state transitions and photosynthetic control. Many of the regulatory roles of cytb6f are facilitated by auxiliary proteins that differ depending upon the species, yet because of their weak and transient nature the structural details of these interactions remain unknown. An apparent key player in the regulatory balance between LET and CET in cyanobacteria is PetP, a ∼10 kDa protein that is also found in red algae but not in green algae and plants. Here, we used cryogenic electron microscopy to determine the structure of the Synechocystis sp. PCC 6803 cytb6f complex in the presence and absence of PetP. Our structures show that PetP interacts with the cytoplasmic side of cytb6f, displacing the C-terminus of the PetG subunit and shielding the C-terminus of cytochrome b6, which binds the heme cn cofactor that is suggested to mediate CET. The structures also highlight key differences in the mode of plastoquinone binding between cyanobacterial and plant cytb6f complexes, which we suggest may reflect the unique combination of photosynthetic and respiratory electron transfer in cyanobacterial thylakoid membranes. The structure of cytb6f from a model cyanobacterial species amenable to genetic engineering will enhance future site-directed mutagenesis studies of structure-function relationships in this crucial ET complex.

PubMed: 35726684
DOI: 10.1042/BCJ20220124

Experimental method

ELECTRON MICROSCOPY (3.15 Å)