4H44

2.70 A Cytochrome b6f Complex Structure From Nostoc PCC 7120

Summary for 4H44

• Entry DOI: 10.2210/pdb4h44/pdb
• Related: 1Q90 1VF5 2D2C 2E74 2E75 2E76 2ZT9 4H0L 4H13
• Descriptor: Cytochrome b6, UNDECYL-MALTOSIDE, PENTADECANE, ... (21 entities in total)
• Functional Keywords: alpha helix, beta-sheet, plastoquinol-plastocyanin oxidoreductase, plastocyanin, thylakoid membranes, photosynthesis
• Biological source: Nostoc; More
• Cellular location: Cellular thylakoid membrane; Multi-pass membrane protein (By similarity): P0A384 Q93SX1; Cellular thylakoid membrane; Single-pass membrane protein (By similarity): Q93SW9 Q93SX0 Q8YVQ2 P0A3Y1 P58246 P61048
• Total number of polymer chains: 8
• Total formula weight: 116452.78

Authors

Hasan, S.S.,Yamashita, E.,Baniulis, D.,Cramer, W.A. (deposition date: 2012-09-16, release date: 2013-02-20, Last modification date: 2023-11-08)

Primary citation

Hasan, S.S.,Yamashita, E.,Baniulis, D.,Cramer, W.A.
Quinone-dependent proton transfer pathways in the photosynthetic cytochrome b6f complex
Proc.Natl.Acad.Sci.USA, 110:4297-4302, 2013

PubMed Abstract: As much as two-thirds of the proton gradient used for transmembrane free energy storage in oxygenic photosynthesis is generated by the cytochrome b6f complex. The proton uptake pathway from the electrochemically negative (n) aqueous phase to the n-side quinone binding site of the complex, and a probable route for proton exit to the positive phase resulting from quinol oxidation, are defined in a 2.70-Å crystal structure and in structures with quinone analog inhibitors at 3.07 Å (tridecyl-stigmatellin) and 3.25-Å (2-nonyl-4-hydroxyquinoline N-oxide) resolution. The simplest n-side proton pathway extends from the aqueous phase via Asp20 and Arg207 (cytochrome b6 subunit) to quinone bound axially to heme c(n). On the positive side, the heme-proximal Glu78 (subunit IV), which accepts protons from plastosemiquinone, defines a route for H(+) transfer to the aqueous phase. These pathways provide a structure-based description of the quinone-mediated proton transfer responsible for generation of the transmembrane electrochemical potential gradient in oxygenic photosynthesis.

PubMed: 23440205
DOI: 10.1073/pnas.1222248110

Experimental method

X-RAY DIFFRACTION (2.7 Å)