4h44 | pdb_00004h44
2.70 A Cytochrome b6f Complex Structure From Nostoc PCC 7120
Structural highlights
Function[PETM_NOSS1] Component of the cytochrome b6-f complex, which mediates electron transfer between photosystem II (PSII) and photosystem I (PSI), cyclic electron flow around PSI, and state transitions (By similarity). [CYF_NOSS1] Component of the cytochrome b6-f complex, which mediates electron transfer between photosystem II (PSII) and photosystem I (PSI), cyclic electron flow around PSI, and state transitions (By similarity). [PETG_NOSS1] Component of the cytochrome b6-f complex, which mediates electron transfer between photosystem II (PSII) and photosystem I (PSI), cyclic electron flow around PSI, and state transitions. PetG is required for either the stability or assembly of the cytochrome b6-f complex (By similarity). [PETD_NOSS1] Component of the cytochrome b6-f complex, which mediates electron transfer between photosystem II (PSII) and photosystem I (PSI), cyclic electron flow around PSI, and state transitions (By similarity). [PETN_NOSS1] Component of the cytochrome b6-f complex, which mediates electron transfer between photosystem II (PSII) and photosystem I (PSI), cyclic electron flow around PSI, and state transitions (By similarity). [CYB6_NOSS1] Component of the cytochrome b6-f complex, which mediates electron transfer between photosystem II (PSII) and photosystem I (PSI), cyclic electron flow around PSI, and state transitions (By similarity). [UCRIA_NOSS1] Component of the cytochrome b6-f complex, which mediates electron transfer between photosystem II (PSII) and photosystem I (PSI), cyclic electron flow around PSI, and state transitions (By similarity). [PETL_NOSS1] Component of the cytochrome b6-f complex, which mediates electron transfer between photosystem II (PSII) and photosystem I (PSI), cyclic electron flow around PSI, and state transitions. PetL is important for photoautotrophic growth as well as for electron transfer efficiency and stability of the cytochrome b6-f complex (By similarity). Publication Abstract from PubMedAs much as two-thirds of the proton gradient used for transmembrane free energy storage in oxygenic photosynthesis is generated by the cytochrome bf 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-A crystal structure and in structures with quinone analog inhibitors at 3.07 A (tridecyl-stigmatellin) and 3.25-A (2-nonyl-4-hydroxyquinoline N-oxide) resolution. The simplest n-side proton pathway extends from the aqueous phase via Asp20 and Arg207 (cytochrome b subunit) to quinone bound axially to heme c. 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. Quinone-dependent proton transfer pathways in the photosynthetic cytochrome b6f complex.,Hasan SS, Yamashita E, Baniulis D, Cramer WA Proc Natl Acad Sci U S A. 2013 Mar 12;110(11):4297-302. doi:, 10.1073/pnas.1222248110. Epub 2013 Feb 25. PMID:23440205[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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