P00167 (CYB5_HUMAN) Reviewed, UniProtKB/Swiss-Prot

Names and origin

Protein names

Recommended name:
Cytochrome b5

Alternative name(s):
Microsomal cytochrome b5 type A
Short name=MCB5

Gene names

Name:	CYB5A
Synonyms:	CYB5

Organism

Homo sapiens (Human) [Reference proteome]

Taxonomic identifier

9606 [NCBI]

Taxonomic lineage

cellular organisms › Eukaryota › Opisthokonta › Metazoa › Eumetazoa › Bilateria › Deuterostomia › Chordata › Craniata › Vertebrata › Gnathostomata › Teleostomi › Euteleostomi › Sarcopterygii › Tetrapoda › Amniota › Mammalia › Theria › Eutheria › Euarchontoglires › Primates › Haplorrhini › Simiiformes › Catarrhini › Hominoidea › Hominidae › Homininae › Homo

Protein attributes

Sequence length	134 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	Cytochrome b5 is a membrane bound hemoprotein which function as an electron carrier for several membrane bound oxygenases.
Subcellular location	Isoform 1: Endoplasmic reticulum membrane; Single-pass membrane protein; Cytoplasmic side. Microsome membrane; Single-pass membrane protein; Cytoplasmic side. Isoform 2: Cytoplasm.
Involvement in disease	Methemoglobinemia CYB5A-related (METHB-CYB5A) [MIM:250790]: A form of methemoglobinemia, a hematologic disease characterized by the presence of excessive amounts of methemoglobin in blood cells, resulting in decreased oxygen carrying capacity of the blood, cyanosis and hypoxia. Note: The disease is caused by mutations affecting the gene represented in this entry. Ref.14
Sequence similarities	Belongs to the cytochrome b5 family. Contains 1 cytochrome b5 heme-binding domain.
Sequence caution	The sequence AAA63169.1 differs from that shown. Reason: Erroneous gene model prediction.

Ontologies

Keywords
Biological process	Electron transport Transport
Cellular component	Cytoplasm Endoplasmic reticulum Membrane Microsome
Coding sequence diversity	Alternative splicing
Domain	Transmembrane Transmembrane helix
Ligand	Heme Iron Metal-binding
PTM	Acetylation
Technical term	3D-structure Complete proteome Direct protein sequencing Reference proteome
Gene Ontology (GO)
Biological_process	L-ascorbic acid metabolic process Traceable author statement. Source: Reactome electron transport chain 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 mitochondrial outer membrane Traceable author statement. Source: Reactome
Molecular_function	aldo-keto reductase (NADP) activity Traceable author statement. Source: Reactome cytochrome-c oxidase activity Traceable author statement Ref.2. Source: ProtInc heme binding Inferred from electronic annotation. Source: InterPro metal ion binding Inferred from electronic annotation. Source: UniProtKB-KW
Complete GO annotation...

Alternative products

This entry describes 3 isoforms produced by alternative splicing. [Align] [Select]

Isoform 1 (identifier: P00167-1)

Also known as: Liver; Membrane-bound;

This isoform has been chosen as the 'canonical' sequence. All positional information in this entry refers to it. This is also the sequence that appears in the downloadable versions of the entry.

Isoform 2 (identifier: P00167-2)

Also known as: Erythrocyte; Cytoplasmic;

The sequence of this isoform differs from the canonical sequence as follows:
     98-98: T → P
     99-134: Missing.

Note: May be produced at very low levels due to a premature stop codon in the mRNA, leading to nonsense-mediated mRNA decay.

Isoform 3 (identifier: P00167-3)

The sequence of this isoform differs from the canonical sequence as follows:
     86-95: Missing.

Note: No experimental confirmation available.

Sequence annotation (Features)

Feature key

Position(s)

Length

Description

Graphical view

Feature identifier

Molecule processing

Initiator methionine

1

1

Removed Ref.9 Ref.10 Ref.11 Ref.12 Ref.13

Chain

2 – 134

133

Cytochrome b5

PRO_0000166010

Regions

Transmembrane

109 – 131

23

Helical; Potential

Domain

9 – 85

77

Cytochrome b5 heme-binding

Sites

Metal binding

44

1

Iron (heme axial ligand)

Metal binding

68

1

Iron (heme axial ligand)

Amino acid modifications

Modified residue

2

1

N-acetylalanine

Modified residue

19

1

N6-acetyllysine By similarity

Natural variations

Alternative sequence

86 – 95

10

Missing in isoform 3.

VSP_045367

Alternative sequence

98

1

T → P in isoform 2.

VSP_001240

Alternative sequence

99 – 134

36

Missing in isoform 2.

VSP_001241

Experimental info

Sequence conflict

2 – 4

3

Missing AA sequence Ref.10

Sequence conflict

4

1

Q → E AA sequence Ref.13

Sequence conflict

15 – 18

4

EEIQ → QEIE AA sequence Ref.10

Sequence conflict

15 – 18

4

EEIQ → QEIE AA sequence Ref.11

Sequence conflict

15 – 18

4

EEIQ → QEIE AA sequence Ref.12

Sequence conflict

22

1

Missing AA sequence Ref.12

Sequence conflict

52

1

R → W in CA771478. Ref.4

Sequence conflict

62

1

N → D AA sequence Ref.10

Sequence conflict

62

1

N → D AA sequence Ref.11

Sequence conflict

62

1

N → D AA sequence Ref.12

Sequence conflict

89 – 91

3

RPK → KPR AA sequence Ref.9

Sequence conflict

89 – 91

3

RPK → KPR AA sequence Ref.10

Sequence conflict

89 – 91

3

RPK → KPR AA sequence Ref.11

Sequence conflict

89 – 91

3

RPK → KPR AA sequence Ref.12

Sequence conflict

122

1

A → V AA sequence Ref.13

Secondary structure

1

.

.

.

.

.

.

.

.

.

.

.

.

.

.

.

.

.

.

.

.

.

.

.

.

.

.

.

134

Helix Strand Turn

Details...

Beta strand

3 – 5

3

Helix

14 – 17

4

Helix

18 – 20

3

Beta strand

25 – 36

12

Turn

38 – 43

6

Helix

49 – 52

4

Beta strand

55 – 58

4

Helix

61 – 65

5

Helix

70 – 75

6

Helix

76 – 78

3

Beta strand

80 – 84

5

Turn

86 – 88

3

Turn

91 – 93

3

Beta strand

96 – 100

5

Sequences

	Sequence		Length	Mass (Da)
	Isoform 1 (Liver) (Membrane-bound) [UniParc]. Last modified January 23, 2007. Version 2. Checksum: B6AD2AB747555048	FASTA	134	15,330
	10 20 30 40 50 60 MAEQSDEAVK YYTLEEIQKH NHSKSTWLIL HHKVYDLTKF LEEHPGGEEV LREQAGGDAT 70 80 90 100 110 120 ENFEDVGHST DAREMSKTFI IGELHPDDRP KLNKPPETLI TTIDSSSSWW TNWVIPAISA 130 VAVALMYRLY MAED
	Isoform 2 (Erythrocyte) (Cytoplasmic) [UniParc]. Checksum: 62D9B54C7BCDF9F3	FASTA	98	11,268
	10 20 30 40 50 60 MAEQSDEAVK YYTLEEIQKH NHSKSTWLIL HHKVYDLTKF LEEHPGGEEV LREQAGGDAT 70 80 90 ENFEDVGHST DAREMSKTFI IGELHPDDRP KLNKPPEP
	Isoform 3 [UniParc]. Checksum: AC952456B4827706	FASTA	124	14,169
	10 20 30 40 50 60 MAEQSDEAVK YYTLEEIQKH NHSKSTWLIL HHKVYDLTKF LEEHPGGEEV LREQAGGDAT 70 80 90 100 110 120 ENFEDVGHST DAREMSKTFI IGELHPETLI TTIDSSSSWW TNWVIPAISA VAVALMYRLY MAED

References

	« Hide 'large scale' referencesShow 'large scale' references »
[1]	"The complete nucleotide sequence of human liver cytochrome b5 mRNA." Yoo M., Steggles A.W. Biochem. Biophys. Res. Commun. 156:576-580(1988) [PubMed] [Europe PMC] [Abstract] Cited for: NUCLEOTIDE SEQUENCE [MRNA] (ISOFORM 1). Tissue: Liver.
[2]	"The human liver and reticulocyte cytochrome b5 mRNAs are products from a single gene." Giordano S.J., Steggles A.W. Biochem. Biophys. Res. Commun. 178:38-44(1991) [PubMed] [Europe PMC] [Abstract] Cited for: NUCLEOTIDE SEQUENCE [MRNA] (ISOFORM 2). Tissue: Erythrocyte.
[3]	"The isolation and characterization of the human cytochrome b5 gene." Li X.R., Giordano S.J., Yoo M., Steggles A.W. Biochem. Biophys. Res. Commun. 209:894-900(1995) [PubMed] [Europe PMC] [Abstract] Cited for: NUCLEOTIDE SEQUENCE [GENOMIC DNA].
[4]	"Endocrine pancreas consortium." Melton D., Brown J., Kenty G., Permutt A., Lee C., Kaestner K., Lemishka I., Scearce M., Brestelli J., Gradwohl G., Clifton S., Hillier L., Marra M., Pape D., Wylie T., Martin J., Blistain A., Schmitt A. , Theising B., Ritter E., Ronko I., Bennett J., Cardenas M., Gibbons M., McCann R., Cole R., Tsagareishvili R., Williams T., Jackson Y., Bowers Y. Submitted (DEC-2002) to the EMBL/GenBank/DDBJ databases Cited for: NUCLEOTIDE SEQUENCE [LARGE SCALE MRNA] (ISOFORM 3). Tissue: Pancreas.
[5]	"Cloning of human full open reading frames in Gateway(TM) system entry vector (pDONR201)." Ebert L., Schick M., Neubert P., Schatten R., Henze S., Korn B. Submitted (JUN-2004) to the EMBL/GenBank/DDBJ databases Cited for: NUCLEOTIDE SEQUENCE [LARGE SCALE MRNA] (ISOFORM 1).
[6]	"DNA sequence and analysis of human chromosome 18." Nusbaum C., Zody M.C., Borowsky M.L., Kamal M., Kodira C.D., Taylor T.D., Whittaker C.A., Chang J.L., Cuomo C.A., Dewar K., FitzGerald M.G., Yang X., Abouelleil A., Allen N.R., Anderson S., Bloom T., Bugalter B., Butler J. , Cook A., DeCaprio D., Engels R., Garber M., Gnirke A., Hafez N., Hall J.L., Norman C.H., Itoh T., Jaffe D.B., Kuroki Y., Lehoczky J., Lui A., Macdonald P., Mauceli E., Mikkelsen T.S., Naylor J.W., Nicol R., Nguyen C., Noguchi H., O'Leary S.B., Piqani B., Smith C.L., Talamas J.A., Topham K., Totoki Y., Toyoda A., Wain H.M., Young S.K., Zeng Q., Zimmer A.R., Fujiyama A., Hattori M., Birren B.W., Sakaki Y., Lander E.S. Nature 437:551-555(2005) [PubMed] [Europe PMC] [Abstract] Cited for: NUCLEOTIDE SEQUENCE [LARGE SCALE GENOMIC DNA].
[7]	Mural R.J., Istrail S., Sutton G.G., Florea L., Halpern A.L., Mobarry C.M., Lippert R., Walenz B., Shatkay H., Dew I., Miller J.R., Flanigan M.J., Edwards N.J., Bolanos R., Fasulo D., Halldorsson B.V., Hannenhalli S., Turner R. , Yooseph S., Lu F., Nusskern D.R., Shue B.C., Zheng X.H., Zhong F., Delcher A.L., Huson D.H., Kravitz S.A., Mouchard L., Reinert K., Remington K.A., Clark A.G., Waterman M.S., Eichler E.E., Adams M.D., Hunkapiller M.W., Myers E.W., Venter J.C. Submitted (JUL-2005) to the EMBL/GenBank/DDBJ databases Cited for: NUCLEOTIDE SEQUENCE [LARGE SCALE GENOMIC DNA].
[8]	"The status, quality, and expansion of the NIH full-length cDNA project: the Mammalian Gene Collection (MGC)." The MGC Project Team Genome Res. 14:2121-2127(2004) [PubMed] [Europe PMC] [Abstract] Cited for: NUCLEOTIDE SEQUENCE [LARGE SCALE MRNA] (ISOFORM 1). Tissue: Uterus.
[9]	"Amino acid sequences of cytochrome b5 from human, porcine, and bovine erythrocytes and comparison with liver microsomal cytochrome b5." Abe K., Kimura S., Kizawa R., Anan F.K., Sugita Y. J. Biochem. 97:1659-1668(1985) [PubMed] [Europe PMC] [Abstract] Cited for: PROTEIN SEQUENCE OF 2-98. Tissue: Erythrocyte.
[10]	"Amino acid sequences of tryptic peptides of cytochromes b5 from microsomes of human, monkey, porcine, and chicken liver." Nobrega F.G., Ozols J. J. Biol. Chem. 246:1706-1717(1971) [PubMed] [Europe PMC] [Abstract] Cited for: PROTEIN SEQUENCE OF 2-91.
[11]	"Cytochrome b5 from a normal human liver. Isolation and the partial amino acid sequence." Ozols J. J. Biol. Chem. 247:2242-2245(1972) [PubMed] [Europe PMC] [Abstract] Cited for: PROTEIN SEQUENCE OF 2-91.
[12]	"Structural studies of cytochrome b5. 3. Sequential studies on human liver cytochrome b5." Rashid M.A., Hagihara B., Kobayashi M., Tani S., Tsugita A. J. Biochem. 74:985-1002(1973) [PubMed] [Europe PMC] [Abstract] Cited for: PROTEIN SEQUENCE OF 2-91.
[13]	"Structure of cytochrome b5 and its topology in the microsomal membrane." Ozols J. Biochim. Biophys. Acta 997:121-130(1989) [PubMed] [Europe PMC] [Abstract] Cited for: PROTEIN SEQUENCE OF 2-36 AND 84-134.
[14]	"A splicing mutation in the cytochrome b5 gene from a patient with congenital methemoglobinemia and pseudohermaphrodism." Giordano S.J., Kaftory A., Steggles A.W. Hum. Genet. 93:568-570(1994) [PubMed] [Europe PMC] [Abstract] Cited for: INVOLVEMENT IN METHB-CYB5A.
[15]	"Initial characterization of the human central proteome." Burkard T.R., Planyavsky M., Kaupe I., Breitwieser F.P., Buerckstuemmer T., Bennett K.L., Superti-Furga G., Colinge J. BMC Syst. Biol. 5:17-17(2011) [PubMed] [Europe PMC] [Abstract] Cited for: IDENTIFICATION BY MASS SPECTROMETRY [LARGE SCALE ANALYSIS].
+	Additional computationally mapped references.

Cross-references

Sequence databases

EMBL
GenBank
DDBJ

M22865 mRNA. Translation: AAA35729.1.
M60174 mRNA. Translation: AAA52165.1.
L39945 , L39792, L39941, L39942, L39943, L39944 Genomic DNA. Translation: AAA63169.1. Sequence problems.
CA771478 mRNA. No translation available.
CR456990 mRNA. Translation: CAG33271.1.
AC090398 Genomic DNA. No translation available.
CH471117 Genomic DNA. Translation: EAW66544.1.
BC015182 mRNA. Translation: AAH15182.1.

IPI

IPI00182933.
IPI00397860.
IPI00645474.

PIR

CBHU5. A28936.
CBHU5E. JN0075.

RefSeq

NP_001177736.1. NM_001190807.2.
NP_001905.1. NM_001914.3.
NP_683725.1. NM_148923.3.

UniGene

Hs.465413.

3D structure databases

PDBe
RCSB PDB
PDBj

Entry	Method	Resolution (Å)	Chain	Positions	PDBsum
2I96	NMR	-	A	1-108	[»]

ProteinModelPortal

P00167.

ModBase

Search...

Protein-protein interaction databases

IntAct

P00167. 3 interactions.

STRING

9606.ENSP00000341625.

PTM databases

PhosphoSite

P00167.

Polymorphism databases

DMDM

117809.

Proteomic databases

PaxDb

P00167.

PRIDE

P00167.

Protocols and materials databases

DNASU

1528.

StructuralBiologyKnowledgebase

Search...

Genome annotation databases

Ensembl

ENST00000340533; ENSP00000341625; ENSG00000166347.
ENST00000397914; ENSP00000381011; ENSG00000166347.
ENST00000494131; ENSP00000436461; ENSG00000166347.

GeneID

1528.

KEGG

hsa:1528.

UCSC

uc002llh.3. human.
uc002lli.3. human.

Organism-specific databases

CTD

1528.

GeneCards

GC18M071920.

HGNC

HGNC:2570. CYB5A.

HPA

CAB006333.

MIM

250790. phenotype.
613218. gene.

neXtProt

NX_P00167.

Orphanet

90796. 46,XY disorder of sex development due to isolated 17, 20 lyase deficiency.
621. Hereditary methemoglobinemia.

PharmGKB

PA27068.

GenAtlas

Search...

Phylogenomic databases

eggNOG

COG5274.

HOGENOM

HOG000039853.

HOVERGEN

HBG002653.

InParanoid

P00167.

OMA

MAEQSDK.

OrthoDB

EOG4S7JRC.

Enzyme and pathway databases

BioCyc

MetaCyc:ENSG00000166347-MONOMER.

Reactome

REACT_111217. Metabolism.

Gene expression databases

ArrayExpress

P00167.

Bgee

P00167.

CleanEx

HS_CYB5A.

Genevestigator

P00167.

GermOnline

ENSG00000166347. Homo sapiens.

Family and domain databases

Gene3D

3.10.120.10. 1 hit.

InterPro

IPR001199. Cyt_B5-like_heme/steroid-bd.
IPR018506. Cyt_B5_heme-BS.
[Graphical view]

Pfam

PF00173. Cyt-b5. 1 hit.
[Graphical view]

PRINTS

PR00363. CYTOCHROMEB5.

SUPFAM

SSF55856. Cyt_B5. 1 hit.

PROSITE

PS00191. CYTOCHROME_B5_1. 1 hit.
PS50255. CYTOCHROME_B5_2. 1 hit.
[Graphical view]

ProtoNet

Search...

Other

ChEMBL

CHEMBL6170.

ChiTaRS

CYB5A. human.

DrugBank

DB01028. Methoxyflurane.

EvolutionaryTrace

P00167.

GenomeRNAi

1528.

NextBio

6325.

SOURCE

Search...

Entry information

Entry name

CYB5_HUMAN

Accession

Primary (citable) accession number: P00167
Secondary accession number(s): A8MV91, F8WEU4, Q6IB14

Entry history

Integrated into UniProtKB/Swiss-Prot:	July 21, 1986
Last sequence update:	January 23, 2007
Last modified:	May 1, 2013
This is version 151 of the entry and version 2 of the sequence. [Complete history]

Entry status

Reviewed (UniProtKB/Swiss-Prot)

Annotation program

Chordata Protein Annotation Program

Disclaimer

Any medical or genetic information present in this entry is provided for research, educational and informational purposes only. It is not in any way intended to be used as a substitute for professional medical advice, diagnosis, treatment or care.