Reviewed, UniProtKB/Swiss-Prot P31480 (CYB6_EUGGR)

Names and origin

Protein names

Recommended name:
    Cytochrome b6

Gene names

Name:

petB

Encoded on

Plastid; Chloroplast

Organism

Euglena gracilis

Taxonomic identifier

3039 [NCBI]

Taxonomic lineage

Eukaryota › Euglenozoa › Euglenida › Euglenales › Euglena

Protein attributes

Sequence length	215 AA.
Sequence status	Complete.
Sequence processing	The displayed sequence is further processed into a mature form.
Protein existence	Evidence at protein level.

General annotation (Comments)

Function	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.
Cofactor	Binds 2 heme groups. One heme group is bound covalently by a single cysteine link, the other one non-covalently By similarity.
Subunit structure	The 4 large subunits of the cytochrome b6-f complex are cytochrome b6, subunit IV (17 kDa polypeptide, petD), cytochrome f and the Rieske protein, while the 4 small subunits are petG, petL, petM and petN. The complex functions as a dimer By similarity.
Subcellular location	Plastid › chloroplast thylakoid membrane; Multi-pass membrane protein By similarity.
Miscellaneous	Heme 1 (or BH or b566) is high-potential and absorbs at about 566 nm, and heme 2 (or BL or b562) is low-potential and absorbs at about 562 nm By similarity.
Sequence similarities	Belongs to the cytochrome b family. PetB subfamily.

Ontologies

Keywords
Biological process	Electron transport Photosynthesis Transport
Cellular component	Chloroplast Membrane Plastid Thylakoid
Domain	Transmembrane
Ligand	Heme Iron Metal-binding
Technical term	Direct protein sequencing
Gene Ontology (GO)
Biological process	photosynthetic electron transport in cytochrome b6/f Ref.3 Non-traceable author statement. Source: UniProtKB respiratory electron transport chain Inferred from electronic annotation. Source: InterPro transport Inferred from electronic annotation. Source: UniProtKB-KW
Cellular component	chloroplast thylakoid membrane Inferred from electronic annotation. Source: UniProtKB-SubCell cytochrome b6f complex Ref.3 Inferred from direct assay. Source: UniProtKB integral to membrane Inferred from electronic annotation. Source: UniProtKB-KW
Molecular function	electron transporter, transferring electrons within cytochrome b6/f complex of photosystem II activity Ref.3 Non-traceable author statement. Source: UniProtKB iron ion binding Inferred from electronic annotation. Source: UniProtKB-KW oxidoreductase activity Inferred from electronic annotation. Source: InterPro
Complete GO annotation...

Sequence annotation (Features)

	Feature key	Position(s)	Length	Description	Graphical view	Feature identifier
Molecule processing
	Initiator methionine	1	1	Removed Ref.3
	Chain	2 – 215	214	Cytochrome b6 HAMAP MF_00633		PRO_0000061793
Regions
	Transmembrane	32 – 52	21	Potential
	Transmembrane	90 – 110	21	Potential
	Transmembrane	116 – 136	21	Potential
	Transmembrane	186 – 206	21	Potential
Sites
	Metal binding	86	1	Iron (heme 2 axial ligand) By similarity
	Metal binding	100	1	Iron (heme 1 axial ligand) By similarity
	Metal binding	187	1	Iron (heme 2 axial ligand) By similarity
	Metal binding	202	1	Iron (heme 1 axial ligand) By similarity
	Binding site	35	1	Heme 1 (covalent; via 1 link) By similarity

Sequences

	Sequence		Length	Mass (Da)
	P31480-1 [UniParc]. Last modified January 23, 2007. Version 3. Checksum: 870C9E08CDFECCCB	FASTA	215	24,385
	10 20 30 40 50 60 MSRVYDWFEE RLEIQAIADD VSSKYVPPHV NIFYCLGGIT FTCFIIQVAT GFAMTFYYRP 70 80 90 100 110 120 TVTEAFLSVK YIMNEVNFGW LIRSIHRWSA SMMVLMMILH VCRVYLTGGF KKPRELTWVT 130 140 150 160 170 180 GIILAILTVS FGVTGYSLPW DQVGYWAVKI VTGVPEAIPL IGNFIVELLR GSVSVGQSTL 190 200 210 TRFYSLHTFV LPLLTATFML GHFLMIRKQG ISGPL

References

	« Hide 'large scale' referencesShow 'large scale' references »
[1]	"Gene structure and expression of a novel Euglena gracilis chloroplast operon encoding cytochrome b6 and the beta and epsilon subunits of the H(+)-ATP synthase complex." Hong L., Hallick R.B. Curr. Genet. 25:270-281(1994) [PubMed: 7923415] [Abstract] Cited for: NUCLEOTIDE SEQUENCE [GENOMIC DNA]. Strain: Z / UTEX 753.
[2]	"Complete sequence of Euglena gracilis chloroplast DNA." Hallick R.B., Hong L., Drager R.G., Favreau M.R., Monfort A., Orsat B., Spielmann A., Stutz E. Nucleic Acids Res. 21:3537-3544(1993) [PubMed: 8346031] [Abstract] Cited for: NUCLEOTIDE SEQUENCE [LARGE SCALE GENOMIC DNA]. Strain: Z / UTEX 753.
[3]	"Cytochrome f and subunit IV, two essential components of the photosynthetic bf complex typically encoded in the chloroplast genome, are nucleus-encoded in Euglena gracilis." Santillan Torres J.L., Atteia A., Claros M.G., Gonzalez-Halphen D. Biochim. Biophys. Acta 1604:180-189(2003) [PubMed: 12837550] [Abstract] Cited for: PROTEIN SEQUENCE OF 2-31, SUBCELLULAR LOCATION.

Cross-references

Sequence databases
EMBLGenBankDDBJ	X70810 Genomic DNA. Translation: CAA50129.1.
PIR	S34548.
RefSeq	NP_041942.1.
3D structure databases
SMR	P31480. Positions 4-215.
ModBase	Search...
Genome annotation databases
GeneID	807480.
Family and domain databases
HAMAP	MF_00633. [Tree]
InterPro	IPR016175. Cyt_b/b6. IPR005797. Cyt_b/b6_N. [Graphical view]
Gene3D	G3DSA:1.20.810.10. Cytochrome_b/b6. 1 hit.
PANTHER	PTHR19271. Cytochrome_b/b6. 1 hit.
Pfam	PF00033. Cytochrom_B_N. 1 hit. [Graphical view]
PROSITE	PS51002. CYTB_NTER. 1 hit. [Graphical view]
ProtoNet	Search...

Entry information

Entry name

CYB6_EUGGR

Accession

Primary (citable) accession number: P31480

Entry history

Integrated into UniProtKB/Swiss-Prot:	July 1, 1993
Last sequence update:	January 23, 2007
Last modified:	June 16, 2009
This is version 65 of the entry and version 3 of the sequence. [Complete history]

Entry status

Reviewed (UniProtKB/Swiss-Prot)

Annotation project

HAMAP (High-quality Automated and Manual Annotation of microbial Proteomes)