ID   CYB6_CHLRE              Reviewed;         215 AA.
AC   Q00471; B7U1F1;
DT   01-DEC-1992, integrated into UniProtKB/Swiss-Prot.
DT   01-DEC-1992, sequence version 1.
DT   27-MAR-2024, entry version 153.
DE   RecName: Full=Cytochrome b6 {ECO:0000255|HAMAP-Rule:MF_00633, ECO:0000303|PubMed:14647374, ECO:0000303|PubMed:15049703};
GN   Name=petB {ECO:0000255|HAMAP-Rule:MF_00633,
GN   ECO:0000303|PubMed:15049703};
OS   Chlamydomonas reinhardtii (Chlamydomonas smithii).
OG   Plastid; Chloroplast.
OC   Eukaryota; Viridiplantae; Chlorophyta; core chlorophytes; Chlorophyceae;
OC   CS clade; Chlamydomonadales; Chlamydomonadaceae; Chlamydomonas.
OX   NCBI_TaxID=3055;
RN   [1]
RP   NUCLEOTIDE SEQUENCE [GENOMIC DNA].
RC   STRAIN=137c / CC-125;
RX   PubMed=2060646; DOI=10.1016/0014-5793(91)80698-3;
RA   Bueschlen S., Choquet Y., Kuras R., Wollman F.A.;
RT   "Nucleotide sequences of the continuous and separated petA, petB and petD
RT   chloroplast genes in Chlamydomonas reinhardtii.";
RL   FEBS Lett. 284:257-262(1991).
RN   [2]
RP   NUCLEOTIDE SEQUENCE [GENOMIC DNA].
RX   PubMed=1581576; DOI=10.1007/bf00019214;
RA   Huang C., Liu X.-Q.;
RT   "Nucleotide sequence of the frxC, petB and trnL genes in the chloroplast
RT   genome of Chlamydomonas reinhardtii.";
RL   Plant Mol. Biol. 18:985-988(1992).
RN   [3]
RP   NUCLEOTIDE SEQUENCE [LARGE SCALE GENOMIC DNA].
RC   STRAIN=CC-503;
RX   PubMed=19473533; DOI=10.1186/1471-2148-9-120;
RA   Smith D.R., Lee R.W.;
RT   "Nucleotide diversity of the Chlamydomonas reinhardtii plastid genome:
RT   addressing the mutational-hazard hypothesis.";
RL   BMC Evol. Biol. 9:120-120(2009).
RN   [4]
RP   IDENTIFICATION, AND COMPLETE PLASTID GENOME.
RX   PubMed=12417694; DOI=10.1105/tpc.006155;
RA   Maul J.E., Lilly J.W., Cui L., dePamphilis C.W., Miller W., Harris E.H.,
RA   Stern D.B.;
RT   "The Chlamydomonas reinhardtii plastid chromosome: islands of genes in a
RT   sea of repeats.";
RL   Plant Cell 14:2659-2679(2002).
RN   [5]
RP   CHARACTERIZATION.
RC   STRAIN=WT12;
RX   PubMed=7493968; DOI=10.1074/jbc.270.49.29342;
RA   Pierre Y., Breyton C., Kramer D., Popot J.-L.;
RT   "Purification and characterization of the cytochrome b6 f complex from
RT   Chlamydomonas reinhardtii.";
RL   J. Biol. Chem. 270:29342-29349(1995).
RN   [6]
RP   MUTAGENESIS OF LEU-204.
RC   STRAIN=137c / CC-125;
RX   PubMed=9037161; DOI=10.1023/a:1005734809834;
RA   Zito F., Kuras R., Choquet Y., Koessel H., Wollman F.-A.;
RT   "Mutations of cytochrome b6 in Chlamydomonas reinhardtii disclose the
RT   functional significance for a proline to leucine conversion by petB editing
RT   in maize and tobacco.";
RL   Plant Mol. Biol. 33:79-86(1997).
RN   [7]
RP   HEME-BINDING, COFACTOR, AND MUTAGENESIS OF CYS-35.
RX   PubMed=15049703; DOI=10.1021/bi036093p;
RA   de Vitry C., Desbois A., Redeker V., Zito F., Wollman F.A.;
RT   "Biochemical and spectroscopic characterization of the covalent binding of
RT   heme to cytochrome b6.";
RL   Biochemistry 43:3956-3968(2004).
RN   [8] {ECO:0007744|PDB:1Q90}
RP   X-RAY CRYSTALLOGRAPHY (3.1 ANGSTROMS) IN COMPLEX WITH 3 HEMES AND OTHER
RP   SUBUNITS OF THE CYTOCHROME B6F COMPLEX, FUNCTION, COFACTOR, AND SUBUNIT.
RX   PubMed=14647374; DOI=10.1038/nature02155;
RA   Stroebel D., Choquet Y., Popot J.-L., Picot D.;
RT   "An atypical haem in the cytochrome b(6)f complex.";
RL   Nature 426:413-418(2003).
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:0000305|PubMed:14647374}.
CC   -!- COFACTOR:
CC       Name=heme b; Xref=ChEBI:CHEBI:60344;
CC         Evidence={ECO:0000269|PubMed:14647374};
CC       Note=Binds 2 heme b groups non-covalently with two histidine residues
CC       as axial ligands. {ECO:0000269|PubMed:14647374};
CC   -!- COFACTOR:
CC       Name=heme c; Xref=ChEBI:CHEBI:61717;
CC         Evidence={ECO:0000269|PubMed:14647374, ECO:0000269|PubMed:15049703};
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:0000269|PubMed:14647374, ECO:0000269|PubMed:15049703};
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. {ECO:0000269|PubMed:14647374}.
CC   -!- SUBCELLULAR LOCATION: Plastid, chloroplast thylakoid membrane; Multi-
CC       pass membrane protein {ECO:0000305}.
CC   -!- PTM: The N-terminus is blocked.
CC   -!- MISCELLANEOUS: Creation by mutagenesis of a Pro residue at position 204
CC       (a codon that is known to be RNA edited to a Leu codon in tobacco and
CC       maize) leads to assembly defective mutants, indicating that the Leu-204
CC       is essential for proper assembly of the cytochrome b6-f complex. This
CC       is probably due to lack of assembly of apocytochrome b6 with one of its
CC       heme groups. {ECO:0000269|PubMed:9037161}.
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:0000255|HAMAP-Rule:MF_00633}.
CC   -!- SIMILARITY: Belongs to the cytochrome b family. PetB subfamily.
CC       {ECO:0000255|HAMAP-Rule:MF_00633}.
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DR   EMBL; X62905; CAA44690.1; -; Genomic_DNA.
DR   EMBL; X72918; CAA51423.1; -; Genomic_DNA.
DR   EMBL; FJ423446; ACJ50098.1; -; Genomic_DNA.
DR   EMBL; BK000554; DAA00911.1; -; Genomic_DNA.
DR   PIR; S21253; S21253.
DR   RefSeq; NP_958365.1; NC_005353.1.
DR   PDB; 1Q90; X-ray; 3.10 A; B=1-215.
DR   PDBsum; 1Q90; -.
DR   AlphaFoldDB; Q00471; -.
DR   SMR; Q00471; -.
DR   DIP; DIP-58593N; -.
DR   IntAct; Q00471; 9.
DR   STRING; 3055.Q00471; -.
DR   PaxDb; 3055-DAA00911; -.
DR   GeneID; 2717017; -.
DR   KEGG; cre:ChreCp008; -.
DR   eggNOG; KOG4663; Eukaryota.
DR   HOGENOM; CLU_031114_0_2_1; -.
DR   InParanoid; Q00471; -.
DR   BioCyc; CHLAMY:CHRECP008-MONOMER; -.
DR   BioCyc; MetaCyc:CHRECP008-MONOMER; -.
DR   EvolutionaryTrace; Q00471; -.
DR   Proteomes; UP000006906; Chloroplast.
DR   GO; GO:0009535; C:chloroplast thylakoid membrane; IEA:UniProtKB-SubCell.
DR   GO; GO:0045158; F:electron transporter, transferring electrons within cytochrome b6/f complex of photosystem II activity; IEA:UniProtKB-UniRule.
DR   GO; GO:0046872; F:metal ion binding; IEA:UniProtKB-KW.
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   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   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   1: Evidence at protein level;
KW   3D-structure; Chloroplast; Electron transport; Heme; Iron; Membrane;
KW   Metal-binding; Photosynthesis; Plastid; Reference proteome; Thylakoid;
KW   Transmembrane; Transmembrane helix; Transport.
FT   CHAIN           1..215
FT                   /note="Cytochrome b6"
FT                   /id="PRO_0000061787"
FT   TRANSMEM        32..52
FT                   /note="Helical"
FT                   /evidence="ECO:0000255|HAMAP-Rule:MF_00633"
FT   TRANSMEM        90..110
FT                   /note="Helical"
FT                   /evidence="ECO:0000255|HAMAP-Rule:MF_00633"
FT   TRANSMEM        116..136
FT                   /note="Helical"
FT                   /evidence="ECO:0000255|HAMAP-Rule:MF_00633"
FT   TRANSMEM        186..206
FT                   /note="Helical"
FT                   /evidence="ECO:0000255|HAMAP-Rule:MF_00633"
FT   BINDING         35
FT                   /ligand="heme c"
FT                   /ligand_id="ChEBI:CHEBI:61717"
FT                   /note="covalent"
FT                   /evidence="ECO:0000269|PubMed:14647374,
FT                   ECO:0000305|PubMed:15049703, ECO:0007744|PDB:1Q90"
FT   BINDING         37
FT                   /ligand="heme b"
FT                   /ligand_id="ChEBI:CHEBI:60344"
FT                   /ligand_label="1"
FT                   /evidence="ECO:0000269|PubMed:14647374,
FT                   ECO:0007744|PDB:1Q90"
FT   BINDING         83
FT                   /ligand="heme b"
FT                   /ligand_id="ChEBI:CHEBI:60344"
FT                   /ligand_label="2"
FT                   /evidence="ECO:0000269|PubMed:14647374,
FT                   ECO:0007744|PDB:1Q90"
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:0000269|PubMed:14647374,
FT                   ECO:0007744|PDB:1Q90"
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:0000269|PubMed:14647374,
FT                   ECO:0007744|PDB:1Q90"
FT   BINDING         103
FT                   /ligand="heme b"
FT                   /ligand_id="ChEBI:CHEBI:60344"
FT                   /ligand_label="1"
FT                   /evidence="ECO:0000269|PubMed:14647374,
FT                   ECO:0007744|PDB:1Q90"
FT   BINDING         114
FT                   /ligand="heme b"
FT                   /ligand_id="ChEBI:CHEBI:60344"
FT                   /ligand_label="1"
FT                   /evidence="ECO:0000269|PubMed:14647374,
FT                   ECO:0007744|PDB:1Q90"
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:0000269|PubMed:14647374,
FT                   ECO:0007744|PDB:1Q90"
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:0000269|PubMed:14647374,
FT                   ECO:0007744|PDB:1Q90"
FT   BINDING         207
FT                   /ligand="heme c"
FT                   /ligand_id="ChEBI:CHEBI:61717"
FT                   /evidence="ECO:0000269|PubMed:14647374,
FT                   ECO:0007744|PDB:1Q90"
FT   BINDING         211
FT                   /ligand="heme c"
FT                   /ligand_id="ChEBI:CHEBI:61717"
FT                   /evidence="ECO:0000269|PubMed:14647374,
FT                   ECO:0007744|PDB:1Q90"
FT   BINDING         212
FT                   /ligand="heme b"
FT                   /ligand_id="ChEBI:CHEBI:60344"
FT                   /ligand_label="1"
FT                   /evidence="ECO:0000269|PubMed:14647374,
FT                   ECO:0007744|PDB:1Q90"
FT   MUTAGEN         35
FT                   /note="C->V: Generates Chlamydomonas strains that are
FT                   unable to grow phototrophically and unable to assemble
FT                   cytochrome b6f complexes."
FT                   /evidence="ECO:0000269|PubMed:15049703"
FT   MUTAGEN         204
FT                   /note="L->P: Leads to defective cytochrome b6-f complex
FT                   assembly, probably due to lack of heme assembly."
FT                   /evidence="ECO:0000269|PubMed:9037161"
FT   HELIX           5..12
FT                   /evidence="ECO:0007829|PDB:1Q90"
FT   HELIX           14..23
FT                   /evidence="ECO:0007829|PDB:1Q90"
FT   HELIX           33..35
FT                   /evidence="ECO:0007829|PDB:1Q90"
FT   HELIX           36..54
FT                   /evidence="ECO:0007829|PDB:1Q90"
FT   TURN            55..57
FT                   /evidence="ECO:0007829|PDB:1Q90"
FT   TURN            62..64
FT                   /evidence="ECO:0007829|PDB:1Q90"
FT   HELIX           65..74
FT                   /evidence="ECO:0007829|PDB:1Q90"
FT   HELIX           79..105
FT                   /evidence="ECO:0007829|PDB:1Q90"
FT   TURN            106..110
FT                   /evidence="ECO:0007829|PDB:1Q90"
FT   STRAND          111..113
FT                   /evidence="ECO:0007829|PDB:1Q90"
FT   HELIX           115..137
FT                   /evidence="ECO:0007829|PDB:1Q90"
FT   HELIX           142..153
FT                   /evidence="ECO:0007829|PDB:1Q90"
FT   HELIX           154..157
FT                   /evidence="ECO:0007829|PDB:1Q90"
FT   HELIX           161..170
FT                   /evidence="ECO:0007829|PDB:1Q90"
FT   STRAND          172..176
FT                   /evidence="ECO:0007829|PDB:1Q90"
FT   HELIX           177..188
FT                   /evidence="ECO:0007829|PDB:1Q90"
FT   HELIX           190..209
FT                   /evidence="ECO:0007829|PDB:1Q90"
SQ   SEQUENCE   215 AA;  24165 MW;  E025FB9ED2ED78B4 CRC64;
     MSKVYDWFEE RLEIQAIADD ITSKYVPPHV NIFYCIGGIT FTCFLVQVAT GFAMTFYYRP
     TVAEAFASVQ YIMTDVNFGW LIRSIHRWSA SMMVLMMVLH VFRVYLTGGF KRPRELTWVT
     GVIMAVCTVS FGVTGYSLPW DQVGYWAVKI VTGVPDAIPG VGGFIVELLR GGVGVGQATL
     TRFYSLHTFV LPLLTAVFML MHFLMIRKQG ISGPL
//