AC MF_00633; DC Protein; auto TR HAMAP; MF_00633; -; 1; level=0 XX Names: Cytb6_f_cytb6 XX ID CYB6 DE RecName: Full=Cytochrome b6; case not GN Name=petB; else case GN Name=petB; Synonyms=cytB; end case XX case CC -!- FUNCTION: Component of the cytochrome bc complex which donates CC electrons to the photosynthetic reaction center. CC -!- COFACTOR: CC Name=heme b; Xref=ChEBI:CHEBI:60344; CC Note=Binds 2 heme b groups non-covalently with two histidine residues CC as axial ligands. CC -!- COFACTOR: CC Name=heme c; Xref=ChEBI:CHEBI:61717; 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 -!- SUBUNIT: The subunits of the cytochrome bc complex are a Rieske Fe-S CC protein (PetC), cytochrome b6 (PetB), subunit IV (PetD), and a diheme CC cytochrome c (PetX). else case not 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 -!- COFACTOR: CC Name=heme b; Xref=ChEBI:CHEBI:60344; CC Note=Binds 2 heme b groups non-covalently with two histidine residues CC as axial ligands. CC -!- COFACTOR: CC Name=heme c; Xref=ChEBI:CHEBI:61717; 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 -!- 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. end case case CC -!- SUBCELLULAR LOCATION: Cell membrane; Multi-pass membrane protein. else case CC -!- SUBCELLULAR LOCATION: Plastid, chloroplast thylakoid membrane; Multi- CC pass membrane protein. else case CC -!- SUBCELLULAR LOCATION: Cell inner membrane; Multi-pass membrane protein. else CC -!- SUBCELLULAR LOCATION: Cellular thylakoid membrane; Multi-pass membrane CC protein. end case 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. CC -!- SIMILARITY: Belongs to the cytochrome b family. PetB subfamily. XX DR Pfam; PF00033; Cytochrom_B_N; 1; trigger=no DR PROSITE; PS51002; CYTB_NTER; 1; trigger=no XX KW Transport KW Electron transport KW Photosynthesis case KW Cell membrane KW Cell inner membrane else case or KW Thylakoid else case KW Cell membrane end case KW Membrane KW Heme KW Metal-binding KW Iron KW Transmembrane KW Transmembrane helix XX case or GO GO:0005886; C:plasma membrane else case GO GO:0009535; C:chloroplast thylakoid membrane else GO GO:0042651; C:thylakoid membrane end case GO GO:0045158; F:electron transporter, transferring electrons within cytochrome b6/f complex of photosystem II activity GO GO:0015979; P:photosynthesis XX FT From: CYB6_CHLRE (Q00471) FT TRANSMEM 32..52 FT /note="Helical" FT TRANSMEM 90..110 FT /note="Helical" FT TRANSMEM 116..136 FT /note="Helical" FT TRANSMEM 186..206 FT /note="Helical" FT BINDING 35 FT /ligand="heme c" FT /ligand_id="ChEBI:CHEBI:61717" FT /note="covalent" FT Condition: C 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 Condition: H 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 Condition: H 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 Condition: H 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 Condition: H XX Size: 213-222; Related: None; Template: Q00471; P00165; P83791; Q57038; Scope: Bacteria; Cyanobacteriota Bacteria; Heliobacteriaceae Plastid Fusion: Nter: None Cter: None Duplicate: None Plasmid: None Comments: In maize and tobacco position 204 has been shown to undergo RNA editing to change the codon from Pro to Leu. It has therefore been suggested to occur in all other plants where this codon is Pro (CCA -> CTA). In C.reinhardtii an engineered Pro mutation at this position is unable to assemble intact complex, giving strength to this suggestion. XX # Revision 1.55 2023/05/15 //