ID CYB6_CYAPA Reviewed; 215 AA. AC P48121; DT 01-FEB-1996, integrated into UniProtKB/Swiss-Prot. DT 01-FEB-1996, sequence version 1. DT 02-SEP-2026, entry version 118. DE RecName: Full=Cytochrome b6; GN Name=petB; OS Cyanophora paradoxa. OG Plastid; Cyanelle. OC Eukaryota; Glaucocystophyceae; Cyanophorales; Cyanophoraceae; Cyanophora. OX NCBI_TaxID=2762; RN [1] RP NUCLEOTIDE SEQUENCE [LARGE SCALE GENOMIC DNA]. RC STRAIN=UTEX LB 555 / Pringsheim; RX DOI=10.1007/BF02669186; RA Stirewalt V.L., Michalowski C.B., Loeffelhardt W., Bohnert H.J., RA Bryant D.A.; RT "Nucleotide sequence of the cyanelle DNA from Cyanophora paradoxa."; RL Plant Mol. Biol. Rep. 13:327-332(1995). RN [2] RP NUCLEOTIDE SEQUENCE [LARGE SCALE GENOMIC DNA]. RC STRAIN=UTEX LB 555 / Pringsheim; RX DOI=10.1007/978-3-642-60885-8_3; RA Loeffelhardt W., Stirewalt V.L., Michalowski C.B., Annarella M., RA Farley J.Y., Schluchter W.M., Chung S., Newmann-Spallart C., Steiner J.M., RA Jakowitsch J., Bohnert H.J., Bryant D.A.; RT "The complete sequence of the cyanelle genome of Cyanophora paradoxa: the RT genetic complexity of a primitive plastid."; RL (In) Schenk H.E.A., Herrmann R., Jeon K.W., Mueller N.E., Schwemmler W. RL (eds.); RL Eukaryotism and symbiosis, pp.40-48, Springer-Verlag, Heidelberg (1997). CC -!- FUNCTION: Component of the cytochrome b6-f complex, which mediates CC electron transfer between photosystem II (PSII) and photosystem I CC (PSI), cyclic electron flow around PSI, and state transitions. CC {ECO:0000250}. CC -!- COFACTOR: CC Name=heme b; Xref=ChEBI:CHEBI:60344; Evidence={ECO:0000255|HAMAP- CC Rule:MF_00633}; CC Note=Binds 2 heme b groups non-covalently with two histidine residues CC as axial ligands. {ECO:0000255|HAMAP-Rule:MF_00633}; CC -!- COFACTOR: CC Name=heme c; Xref=ChEBI:CHEBI:61717; Evidence={ECO:0000255|HAMAP- CC Rule:MF_00633}; CC Note=Binds one heme group covalently by a single cysteine link with no CC axial amino acid ligand. This heme was named heme ci. CC {ECO:0000255|HAMAP-Rule:MF_00633}; CC -!- SUBUNIT: The 4 large subunits of the cytochrome b6-f complex are CC cytochrome b6, subunit IV (17 kDa polypeptide, PetD), cytochrome f and CC the Rieske protein, while the 4 small subunits are PetG, PetL, PetM and CC PetN. The complex functions as a dimer (By similarity). {ECO:0000250}. CC -!- SUBCELLULAR LOCATION: Plastid, cyanelle thylakoid membrane CC {ECO:0000250}; Multi-pass membrane protein {ECO:0000250}. CC -!- MISCELLANEOUS: Heme 1 (or BH or b566) is high-potential and absorbs at CC about 566 nm, and heme 2 (or BL or b562) is low-potential and absorbs CC at about 562 nm. {ECO:0000250}. CC -!- SIMILARITY: Belongs to the cytochrome b family. PetB subfamily. CC {ECO:0000305}. CC --------------------------------------------------------------------------- CC Copyrighted by the UniProt Consortium, see https://www.uniprot.org/terms CC Distributed under the Creative Commons Attribution (CC BY 4.0) License CC --------------------------------------------------------------------------- DR EMBL; U30821; AAA81206.1; -; Genomic_DNA. DR PIR; T06863; T06863. DR RefSeq; NP_043175.1; NC_001675.1. DR AlphaFoldDB; P48121; -. DR SMR; P48121; -. DR GeneID; 801518; -. DR GO; GO:0033115; C:cyanelle thylakoid membrane; IEA:UniProtKB-SubCell. DR GO; GO:0009055; F:electron transfer activity; IEA:UniProtKB-UniRule. DR GO; GO:0016491; F:oxidoreductase activity; IEA:InterPro. DR GO; GO:0015979; P:photosynthesis; IEA:UniProtKB-UniRule. DR GO; GO:0022904; P:respiratory electron transport chain; IEA:InterPro. DR CDD; cd00284; Cytochrome_b_N; 1. DR FunFam; 1.20.810.10:FF:000001; Cytochrome b6; 1. DR Gene3D; 1.20.810.10; Cytochrome Bc1 Complex, Chain C; 1. DR HAMAP; MF_00633; Cytb6_f_cytb6; 1. DR InterPro; IPR005797; Cyt_b/b6_N. DR InterPro; IPR023530; Cyt_B6_PetB. DR InterPro; IPR027387; Cytb/b6-like_sf. DR InterPro; IPR048259; Cytochrome_b_N_euk/bac. DR InterPro; IPR016174; Di-haem_cyt_TM. DR NCBIfam; NF002990; PRK03735.1; 1. DR PANTHER; PTHR19271; CYTOCHROME B; 1. DR PANTHER; PTHR19271:SF16; CYTOCHROME B; 1. DR Pfam; PF00033; Cytochrome_B; 1. DR PIRSF; PIRSF000032; Cytochrome_b6; 1. DR SUPFAM; SSF81342; Transmembrane di-heme cytochromes; 1. DR PROSITE; PS51002; CYTB_NTER; 1. PE 3: Inferred from homology; KW Cyanelle; Electron transport; Heme; Iron; Membrane; Metal-binding; KW Photosynthesis; Plastid; Thylakoid; Transmembrane; Transmembrane helix; KW Transport. FT CHAIN 1..215 FT /note="Cytochrome b6" FT /id="PRO_0000061792" FT TRANSMEM 32..52 FT /note="Helical" FT /evidence="ECO:0000255" FT TRANSMEM 90..110 FT /note="Helical" FT /evidence="ECO:0000255" FT TRANSMEM 116..136 FT /note="Helical" FT /evidence="ECO:0000255" FT TRANSMEM 186..206 FT /note="Helical" FT /evidence="ECO:0000255" FT BINDING 35 FT /ligand="heme c" FT /ligand_id="ChEBI:CHEBI:61717" FT /note="covalent" FT /evidence="ECO:0000255|HAMAP-Rule:MF_00633" FT BINDING 86 FT /ligand="heme b" FT /ligand_id="ChEBI:CHEBI:60344" FT /ligand_label="2" FT /ligand_part="Fe" FT /ligand_part_id="ChEBI:CHEBI:18248" FT /note="axial binding residue" FT /evidence="ECO:0000255|HAMAP-Rule:MF_00633" FT BINDING 100 FT /ligand="heme b" FT /ligand_id="ChEBI:CHEBI:60344" FT /ligand_label="1" FT /ligand_part="Fe" FT /ligand_part_id="ChEBI:CHEBI:18248" FT /note="axial binding residue" FT /evidence="ECO:0000255|HAMAP-Rule:MF_00633" FT BINDING 187 FT /ligand="heme b" FT /ligand_id="ChEBI:CHEBI:60344" FT /ligand_label="2" FT /ligand_part="Fe" FT /ligand_part_id="ChEBI:CHEBI:18248" FT /note="axial binding residue" FT /evidence="ECO:0000255|HAMAP-Rule:MF_00633" FT BINDING 202 FT /ligand="heme b" FT /ligand_id="ChEBI:CHEBI:60344" FT /ligand_label="1" FT /ligand_part="Fe" FT /ligand_part_id="ChEBI:CHEBI:18248" FT /note="axial binding residue" FT /evidence="ECO:0000255|HAMAP-Rule:MF_00633" SQ SEQUENCE 215 AA; 24189 MW; B640C8B9421E2B2A CRC64; MSKVYDWFQE RLEIQAIADD ITSKYVPPHV NIFYCLGGIT LTCFLVQVAT GFAMTFYYRP TVTEAFASVQ YIMTDVNFGW LIRSTHRWSA SMMVLMMILH VFRVYLTGGF KKPRELTWVV GVILAVITVS FGVTGYSLPW DQVGYWAVKI VTGVPEAIPV IGSNVVELLR GSVSVGQSTL TRFYSLHTFV LPLLSAVFML VHFLLIRKQG ISGPL //