Reviewed, UniProtKB/Swiss-Prot P00169 (CYB5_RABIT)

Names and origin

Protein names

Recommended name:
    Cytochrome b5

Gene names

Name:	CYB5A
Synonyms:	CYB5

Organism

Oryctolagus cuniculus (Rabbit)

Taxonomic identifier

9986 [NCBI]

Taxonomic lineage

Eukaryota › Metazoa › Chordata › Craniata › Vertebrata › Euteleostomi › Mammalia › Eutheria › Euarchontoglires › Glires › Lagomorpha › Leporidae › Oryctolagus

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	Endoplasmic reticulum membrane; Single-pass membrane protein; Cytoplasmic side. Microsome membrane; Single-pass membrane protein; Cytoplasmic side.
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
Coding sequence diversity	Alternative splicing
Domain	Transmembrane
Ligand	Heme Iron Metal-binding
PTM	Acetylation
Technical term	3D-structure Direct protein sequencing
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...

Alternative products

This entry describes 2 isoforms produced by alternative splicing. [Align] [Select]

Isoform 1 (identifier: P00169-1)

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: P00169-2)

Also known as: Erythrocyte; Cytoplasmic;

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

Sequence annotation (Features)

Feature key

Position(s)

Length

Description

Graphical view

Feature identifier

Molecule processing

Initiator methionine

1

1

Removed Ref.8

Chain

2 – 134

133

Cytochrome b5

PRO_0000166013

Regions

Transmembrane

109 – 131

23

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 Ref.8

Modified residue

19

1

N6-acetyllysine By similarity

Natural variations

Alternative sequence

98

1

T → P in isoform 2.

VSP_001244

Alternative sequence

99 – 134

36

Missing in isoform 2.

VSP_001245

Experimental info

Sequence conflict

62

1

N → D Ref.3

Sequence conflict

62

1

N → D Ref.5

Sequence conflict

104

1

D → N AA sequence Ref.6

Secondary structure

1

.

.

.

.

.

.

.

.

.

.

.

.

.

.

.

.

.

.

.

.

134

Helix Strand Turn

Details...

Helix

14 – 17

4

Beta strand

27 – 36

10

Helix

38 – 40

3

Turn

41 – 43

3

Beta strand

44 – 46

3

Helix

49 – 53

5

Turn

54 – 56

3

Helix

60 – 66

7

Helix

70 – 79

10

Beta strand

80 – 84

5

Helix

86 – 88

3

Turn

89 – 91

3

Sequences

	Sequence		Length	Mass (Da)
	Isoform 1 (Liver) (Membrane-bound) [UniParc]. Last modified January 23, 2007. Version 4. Checksum: B748AE9D32FA5E46	FASTA	134	15,349
	10 20 30 40 50 60 MAAQSDKDVK YYTLEEIKKH NHSKSTWLIL HHKVYDLTKF LEEHPGGEEV LREQAGGDAT 70 80 90 100 110 120 ENFEDVGHST DARELSKTFI IGELHPDDRS KLSKPMETLI TTVDSNSSWW TNWVIPAISA 130 LIVALMYRLY MADD
	Isoform 2 (Erythrocyte) (Cytoplasmic). Checksum: C3D197FD9C921C1D	FASTA	98	11,232
	10 20 30 40 50 60 MAAQSDKDVK YYTLEEIKKH NHSKSTWLIL HHKVYDLTKF LEEHPGGEEV LREQAGGDAT 70 80 90 ENFEDVGHST DARELSKTFI IGELHPDDRS KLSKPMEP

References

[1]	"The nucleotide sequence of rabbit liver cytochrome b5 mRNA." Dariush N., Fisher C.W., Steggles A.W. Protein Seq. Data Anal. 1:351-353(1988) [PubMed: 3222252] [Abstract] Cited for: NUCLEOTIDE SEQUENCE [MRNA] (ISOFORM 1).
[2]	"Molecular cloning of rabbit cytochrome b5 genes: evidence for the occurrence of two separate genes encoding the soluble and microsomal forms." Takamatsu H., Kozutsumi Y., Suzuki A., Kawasaki T. Biochem. Biophys. Res. Commun. 185:845-851(1992) [PubMed: 1627141] [Abstract] Cited for: NUCLEOTIDE SEQUENCE [MRNA] (ISOFORM 2). Strain: New Zealand white.
[3]	"Primary structure of rabbit liver cytochrome b5." Tsugita A., Kobayashi M., Kajihara T., Hagihara B. J. Biochem. 64:727-730(1968) [PubMed: 5709273] [Abstract] Cited for: PROTEIN SEQUENCE OF 9-46 AND 50-91.
[4]	"Comparative study of the primary structures of cytochrome b5 from four species." Tsugita A., Kobayashi M., Tani S., Kyo S., Rashid M.A., Yoshida Y., Kajihara T., Hagihara B. Proc. Natl. Acad. Sci. U.S.A. 67:442-447(1970) [PubMed: 5272324] [Abstract] Cited for: PROTEIN SEQUENCE OF 7-8 AND 47-49.
[5]	"Amino acid sequence of rabbit liver microsomal cytochrome b5." Ozols J. J. Biol. Chem. 245:4863-4874(1970) [PubMed: 5506260] [Abstract] Cited for: PROTEIN SEQUENCE OF 5-98.
[6]	"Primary structure of the membrane-binding segment of rabbit cytochrome b5." Kondo K., Tajima S., Sato R., Narita K. J. Biochem. 86:1119-1128(1979) [PubMed: 500581] [Abstract] Cited for: PROTEIN SEQUENCE OF 92-134.
[7]	"Amino acid sequence of the membranous segment of rabbit liver cytochrome b5. Methodology for separation of hydrophobic peptides." Takagaki Y., Gerber G.E., Nihei K., Khorana H.G. J. Biol. Chem. 255:1536-1541(1980) [PubMed: 7354043] [Abstract] Cited for: PROTEIN SEQUENCE OF 99-134.
[8]	"Structure of cytochrome b5 and its topology in the microsomal membrane." Ozols J. Biochim. Biophys. Acta 997:121-130(1989) [PubMed: 2752049] [Abstract] Cited for: PROTEIN SEQUENCE OF 2-11.
[9]	"Solution structure of oxidized microsomal rabbit cytochrome b5 factors determining the heterogeneous binding of the heme." Banci L., Bertini I., Rosato A., Scacchieri S. Eur. J. Biochem. 267:755-766(2000) [PubMed: 10651812] [Abstract] Cited for: STRUCTURE BY NMR OF 7-100.

Cross-references

Sequence databases

EMBLGenBankDDBJ

M24844 mRNA. Translation: AAB03878.1.
D10901 mRNA. Translation: BAA01712.1.

PIR

JN0316.
CBRB5. S03373.

3D structure databases

PDBPDBe

Entry	Method	Resolution (Å)	Chain	Positions	PDBsum
1DO9	NMR	-	A	6-99	[»]

ModBase

Search...

Phylogenomic databases

HOVERGEN

P00169.

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_RABIT

Accession

Primary (citable) accession number: P00169
Secondary accession number(s): Q28726

Entry history

Integrated into UniProtKB/Swiss-Prot:	July 21, 1986
Last sequence update:	January 23, 2007
Last modified:	June 16, 2009
This is version 87 of the entry and version 4 of the sequence. [Complete history]

Entry status

Reviewed (UniProtKB/Swiss-Prot)

Annotation project

HPI (Human Proteome Initiative)