Reviewed, UniProtKB/Swiss-Prot P49098 (CYB5_TOBAC)

Names and origin

Protein names	Recommended name:     Cytochrome b5
Organism	Nicotiana tabacum (Common tobacco)
Taxonomic identifier	4097 [NCBI]
Taxonomic lineage	Eukaryota › Viridiplantae › Streptophyta › Embryophyta › Tracheophyta › Spermatophyta › Magnoliophyta › eudicotyledons › core eudicotyledons › asterids › lamiids › Solanales › Solanaceae › Nicotianoideae › Nicotianeae › Nicotiana

Protein attributes

Sequence length	136 AA.
Sequence status	Complete.
Sequence processing	The displayed sequence is not processed.
Protein existence	Evidence at transcript level.

General annotation (Comments)

Function	Cytochrome b5 is a membrane bound hemoprotein which function as an electron carrier for several membrane bound oxygenases. May play a key role in the modification by desaturation of fatty acids in the endoplasmic reticulum, which in the developing seed is utilized for membrane synthesis and in the developmentally regulated production of large amounts of storage lipids. Is involved in the reduction of cytochrome P-450 and may therefore be involved in flavonoid biosynthesis in the petals.
Subcellular location	Endoplasmic reticulum membrane; Single-pass membrane protein; Cytoplasmic side By similarity. Microsome membrane; Single-pass membrane protein; Cytoplasmic side By similarity.
Tissue specificity	Is highly expressed in developing seeds, moderately expressed in flowers, and is expressed at low levels in the leaf.
Sequence similarities	Belongs to the cytochrome b5 family. Contains 1 cytochrome b5 heme-binding domain.

Ontologies

Keywords
Biological process	Electron transport Transport
Cellular component	Endoplasmic reticulum Membrane Microsome
Domain	Transmembrane
Ligand	Heme Iron Metal-binding
Gene Ontology (GO)
Biological process	electron transport chain Inferred from electronic annotation. Source: UniProtKB-KW transport Inferred from electronic annotation. Source: UniProtKB-KW
Cellular component	endoplasmic reticulum membrane Inferred from electronic annotation. Source: UniProtKB-SubCell integral to membrane Inferred from electronic annotation. Source: UniProtKB-KW microsome Inferred from electronic annotation. Source: UniProtKB-SubCell
Molecular function	heme binding Inferred from electronic annotation. Source: InterPro
Complete GO annotation...

Sequence annotation (Features)

	Feature key	Position(s)	Length	Description	Graphical view	Feature identifier
Molecule processing
	Chain	1 – 136	136	Cytochrome b5		PRO_0000166025
Regions
	Transmembrane	107 – 127	21	Potential
	Domain	5 – 81	77	Cytochrome b5 heme-binding
Sites
	Metal binding	40	1	Iron (heme axial ligand) By similarity
	Metal binding	64	1	Iron (heme axial ligand) By similarity
Experimental info
	Sequence conflict	10 – 11	2	LA → EF in CAA48240. Ref.1
	Sequence conflict	105	1	Missing in CAA48240. Ref.1

Sequences

	Sequence		Length	Mass (Da)
	P49098-1 [UniParc]. Last modified February 1, 1996. Version 1. Checksum: DACE9EA695B2835F	FASTA	136	14,979
	10 20 30 40 50 60 MGGETKVFTL AEVSQHNNAK DCWLVISGKV YDVTKFLDDH PGGDEVLLSA TGKDATDDFE 70 80 90 100 110 120 DVGHSSSARA MLDEYYVGDI DSATIPTKTK YTPPNQPHYN QDKTSEFVVK LLQFLVPLII 130 LGVAFGIRFY TKQSSA

References

[1]	"Tobacco cytochrome b5: cDNA isolation, expression analysis and in vitro protein targeting." Smith M.A., Stobart A.K., Shewry P.R., Napier J.A. Plant Mol. Biol. 25:527-537(1994) [PubMed: 8049375] [Abstract] Cited for: NUCLEOTIDE SEQUENCE [MRNA]. Tissue: Leaf.

Cross-references

Sequence databases
EMBLGenBankDDBJ	X71441 mRNA. Translation: CAA50575.1. Different initiation. X68140 mRNA. Translation: CAA48240.1.
PIR	S46306.
3D structure databases
HSSP	HSSP built from PDB template 1B5M based on UniProtKB P04166.
ModBase	Search...
Family and domain databases
InterPro	IPR001199. Cyt_B5. IPR018506. Cyt_B5_heme-BS. [Graphical view]
Gene3D	G3DSA:3.10.120.10. Cyt_B5. 1 hit.
Pfam	PF00173. Cyt-b5. 1 hit. [Graphical view]
PRINTS	PR00363. CYTOCHROMEB5.
ProDom	PD000612. Cyt_B5. 1 hit. [Graphical view] [Entries sharing at least one domain]
PROSITE	PS00191. CYTOCHROME_B5_1. 1 hit. PS50255. CYTOCHROME_B5_2. 1 hit. [Graphical view]
ProtoNet	Search...

Entry information

Entry name

CYB5_TOBAC

Accession

Primary (citable) accession number: P49098

Entry history

Integrated into UniProtKB/Swiss-Prot:	February 1, 1996
Last sequence update:	February 1, 1996
Last modified:	June 16, 2009
This is version 60 of the entry and version 1 of the sequence. [Complete history]

Entry status

Reviewed (UniProtKB/Swiss-Prot)

Annotation project

PPAP (Plant Proteome Annotation Project)