Cytochrome b5: Difference between revisions

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{{DISPLAYTITLE:Cytochrome b<sub>5</sub>}}
{{infobox protein
{{infobox protein
| Name = Cytochrome b5
| Name = Cytochrome b5
Line 24: Line 25:
| InterPro = IPR001199  
| InterPro = IPR001199  
| PROSITE = PDOC00170  
| PROSITE = PDOC00170  
| PDB = {{PDB2|1aqa}}, {{PDB2|1aw3}}, {{PDB2|1awp}}, {{PDB2|1axx}}, {{PDB2|1b5a}}, {{PDB2|1b5b}}, {{PDB2|1b5m}}, {{PDB2|1bfx}}, {{PDB2|1blv}}, {{PDB2|1cxy}}, {{PDB2|1cyo}}, {{PDB2|1do9}}, {{PDB2|1ehb}}, {{PDB2|1es1}}, {{PDB2|1eue}}, {{PDB2|1f03}}, {{PDB2|1f04}}, {{PDB2|1fcb}}, {{PDB2|1hko}}, {{PDB2|1i5u}}, {{PDB2|1i87}}, {{PDB2|1i8c}}, {{PDB2|1ib7}}, {{PDB2|1icc}}, {{PDB2|1iet}}, {{PDB2|1ieu}}, {{PDB2|1j03}}, {{PDB2|1j0q}}, {{PDB2|1jex}}, {{PDB2|1kbi}}, {{PDB2|1kbj}}, {{PDB2|1lco}}, {{PDB2|1ldc}}, {{PDB2|1lj0}}, {{PDB2|1lqx}}, {{PDB2|1lr6}}, {{PDB2|1ltd}}, {{PDB2|1m20}}, {{PDB2|1m2i}}, {{PDB2|1m2m}}, {{PDB2|1m59}}, {{PDB2|1mj4}}, {{PDB2|1mny}}, {{PDB2|1nx7}}, {{PDB2|1qcw}}, {{PDB2|1sh4}}, {{PDB2|1sox}}, {{PDB2|1sze}}, {{PDB2|1szf}}, {{PDB2|1szg}}, {{PDB2|1t0g}}, {{PDB2|1u9m}}, {{PDB2|1u9u}}, {{PDB2|1x3x}}, {{PDB2|2axx}}, {{PDB2|2i89}}, {{PDB2|2ibj}}, {{PDB2|2oz0}} }}
| PDB =  
|Membranome superfamily = 211
}}


'''Cytochromes ''b''<sub>5</sub>''' are ubiquitous [[electron transport]] [[hemoprotein]]s found in [[animal]]s, [[plant]]s, [[fungi]] and [[purple bacteria|purple phototrophic bacteria]]. The [[microsome|microsomal]] and [[mitochondria]]l variants are membrane-bound, while bacterial and those from [[erythrocyte]]s and other [[Biological tissue#Animal tissues|animal tissues]] are water-soluble. The family of cytochrome ''b''<sub>5</sub>-like proteins includes (besides cytochrome ''b''<sub>5</sub> itself) hemoprotein domains covalently associated with other redox domains in flavocytochrome cytochrome ''b''<sub>2</sub> (<small>L</small>-lactate dehydrogenase; {{EC number|1.1.2.3}}), sulfite oxidase ({{EC number|1.8.3.1}}), plant and fungal nitrate reductases ({{EC number|1.7.1.1}}, {{EC number|1.7.1.2}}, {{EC number|1.7.1.3}}), and plant and fungal cytochrome ''b''<sub>5</sub>/acyl lipid desaturase fusion proteins.
'''Cytochromes ''b''<sub>5</sub>''' are ubiquitous [[electron transport]] [[hemoprotein]]s found in [[animal]]s, [[plant]]s, [[fungi]] and [[purple bacteria|purple phototrophic bacteria]]. The [[microsome|microsomal]] and [[mitochondria]]l variants are membrane-bound, while bacterial and those from [[erythrocyte]]s and other [[Biological tissue#Animal tissues|animal tissues]] are water-soluble. The family of cytochrome ''b''<sub>5</sub>-like proteins includes (besides cytochrome ''b''<sub>5</sub> itself) hemoprotein domains covalently associated with other redox domains in flavocytochrome cytochrome ''b''<sub>2</sub> (<small>L</small>-lactate dehydrogenase; {{EC number|1.1.2.3}}), sulfite oxidase ({{EC number|1.8.3.1}}), plant and fungal nitrate reductases ({{EC number|1.7.1.1}}, {{EC number|1.7.1.2}}, {{EC number|1.7.1.3}}), and plant and fungal cytochrome ''b''<sub>5</sub>/acyl lipid desaturase fusion proteins.


==Structure==
== Structure ==


3-D structures of a number of cytochrome ''b''<sub>5</sub> and yeast flavocytochrome ''b''<sub>2</sub> are known. The fold belongs to the α+β class, with two hydrophobic cores on each side of a β-sheet. The larger hydrophobic core constitutes the heme-binding pocket, closed off on each side by a pair of helices connected by a turn. The smaller hydrophobic core may have only a structural role and is formed by spatially close N-terminal and C-terminal segments. The two [[histidine]] residues provide the fifth and sixth heme ligands, and the propionate edge of the heme group lies at the opening of the heme crevice. Two isomers of cytochrome ''b''<sub>5</sub>, referred to as the A (major) and B (minor) forms, differ by a 180° rotation of the heme about an axis defined by the α- and γ-meso carbons.
3-D structures of a number of cytochrome ''b''<sub>5</sub> and yeast flavocytochrome ''b''<sub>2</sub> are known. The fold belongs to the α+β class, with two hydrophobic cores on each side of a β-sheet. The larger hydrophobic core constitutes the heme-binding pocket, closed off on each side by a pair of helices connected by a turn. The smaller hydrophobic core may have only a structural role and is formed by spatially close N-terminal and C-terminal segments. The two [[histidine]] residues provide the fifth and sixth heme ligands, and the propionate edge of the heme group lies at the opening of the heme crevice. Two isomers of cytochrome ''b''<sub>5</sub>, referred to as the A (major) and B (minor) forms, differ by a 180° rotation of the heme about an axis defined by the α- and γ-meso carbons.
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: linoleoyl-CoA + 2 ferrocytochrome ''b''<sub>5</sub> + O<sub>2</sub> + 2 H<sup>+</sup> → γ-linolenoyl-CoA + 2 ferricytochrome ''b''<sub>5</sub> + H<sub>2</sub>O
: linoleoyl-CoA + 2 ferrocytochrome ''b''<sub>5</sub> + O<sub>2</sub> + 2 H<sup>+</sup> → γ-linolenoyl-CoA + 2 ferricytochrome ''b''<sub>5</sub> + H<sub>2</sub>O


==See also==
== See also ==
* [[Cytochrome b5 deficiency|Cytochrome b<sub>5</sub> deficiency]]
* [[P450-containing systems]]
* [[P450-containing systems]]
* [[Cytochrome b5, type A]]
* [[Cytochrome b5, type A|Cytochrome b<sub>5</sub>, type A]]


==References==
== References ==
* {{cite journal | author=Lederer, F. | title=The cytochrome ''b''<sub>5</sub>-fold: an adaptable module | journal=Biochimie | year=1994 | volume=76 | pages=674–692 | pmid=7893819 | doi=10.1016/0300-9084(94)90144-9 | issue=7}}
* {{cite journal | vauthors = Lederer F | title = The cytochrome b5-fold: an adaptable module | journal = Biochimie | volume = 76 | issue = 7 | pages = 674–92 | year = 1994 | pmid = 7893819 | doi = 10.1016/0300-9084(94)90144-9 }}
* {{cite journal | author=Napier, J.A., Michaelson, L.V. and Sayanova, O. | title=The role of cytochrome ''b''<sub>5</sub> fusion desaturases in the synthesis of polyunsaturated fatty acids | journal=Prostaglandins, Leukotrienes and Essential Fatty Acids | year=2003 | volume=68 | pages=135–143 | pmid=12538077 | doi=10.1016/S0952-3278(02)00263-6 | issue=2}}
* {{cite journal | vauthors = Napier JA, Michaelson LV, Sayanova O | title = The role of cytochrome b5 fusion desaturases in the synthesis of polyunsaturated fatty acids | journal = Prostaglandins, Leukotrienes, and Essential Fatty Acids | volume = 68 | issue = 2 | pages = 135–43 | date = February 2003 | pmid = 12538077 | doi = 10.1016/S0952-3278(02)00263-6 }}
* {{cite journal | author=Rivera, M., Barillas-Mury, C., Christensen, K.A., Little, J.W., Wells, M.A. and Walker, F.A. | title=Gene synthesis, bacterial expression, and <sup>1</sup>H NMR spectroscopic studies of the rat outer mitochondrial membrane cytochrome ''b''<sub>5</sub> | journal=Biochemistry | year=1992 | volume=31 | pages=12233–12240 | pmid=1333795 | doi=10.1021/bi00163a037 | issue=48}}
* {{cite journal | vauthors = Rivera M, Barillas-Mury C, Christensen KA, Little JW, Wells MA, Walker FA | title = Gene synthesis, bacterial expression, and 1H NMR spectroscopic studies of the rat outer mitochondrial membrane cytochrome b5 | journal = Biochemistry | volume = 31 | issue = 48 | pages = 12233–40 | date = December 1992 | pmid = 1333795 | doi = 10.1021/bi00163a037 }}
* {{cite journal |author1=Schenkman, J.B.  |author2=Jansson, I. | title=The many roles of cytochrome ''b''<sub>5</sub> | journal=Pharmacol. Ther. | year=2003 | volume=97 | pages=139–152 | pmid=12559387 | doi=10.1016/S0163-7258(02)00327-3 | issue=2}}
* {{cite journal | vauthors = Schenkman JB, Jansson I | title = The many roles of cytochrome b5 | journal = Pharmacology & Therapeutics | volume = 97 | issue = 2 | pages = 139–52 | date = February 2003 | pmid = 12559387 | doi = 10.1016/S0163-7258(02)00327-3 }}


==External links==
== External links ==
* {{PDB|1B5A}} – Solution structure of rat cytochrome ''b''<sub>5</sub> (form A)
* {{PDB|1B5A}} – Solution structure of rat cytochrome ''b''<sub>5</sub> (form A)
* {{PDB|1B5B}} – Solution structure of rat cytochrome ''b''<sub>5</sub> (form B)
* {{PDB|1B5B}} – Solution structure of rat cytochrome ''b''<sub>5</sub> (form B)

Latest revision as of 08:59, 9 January 2019

Cytochrome b5
File:CytB5 1icc.png
Cytochrome B5 (rat) bound to its cofactor. Haem in black, iron in orange and iron-binding histidine residues shown as sticks. (PDB: 1ICC​)
Identifiers
SymbolCYB5A
Alt. symbolsCYB5
Entrez1528
HUGO2570
OMIM250790
PDB1JEX
RefSeqNM_001914
UniProtP00167
Other data
LocusChr. 18 q23
Cytochrome b5
Identifiers
SymbolCyt_B5
PfamPF00173
InterProIPR001199
PROSITEPDOC00170
Membranome211

Cytochromes b5 are ubiquitous electron transport hemoproteins found in animals, plants, fungi and purple phototrophic bacteria. The microsomal and mitochondrial variants are membrane-bound, while bacterial and those from erythrocytes and other animal tissues are water-soluble. The family of cytochrome b5-like proteins includes (besides cytochrome b5 itself) hemoprotein domains covalently associated with other redox domains in flavocytochrome cytochrome b2 (L-lactate dehydrogenase; EC 1.1.2.3), sulfite oxidase (EC 1.8.3.1), plant and fungal nitrate reductases (EC 1.7.1.1, EC 1.7.1.2, EC 1.7.1.3), and plant and fungal cytochrome b5/acyl lipid desaturase fusion proteins.

Structure

3-D structures of a number of cytochrome b5 and yeast flavocytochrome b2 are known. The fold belongs to the α+β class, with two hydrophobic cores on each side of a β-sheet. The larger hydrophobic core constitutes the heme-binding pocket, closed off on each side by a pair of helices connected by a turn. The smaller hydrophobic core may have only a structural role and is formed by spatially close N-terminal and C-terminal segments. The two histidine residues provide the fifth and sixth heme ligands, and the propionate edge of the heme group lies at the opening of the heme crevice. Two isomers of cytochrome b5, referred to as the A (major) and B (minor) forms, differ by a 180° rotation of the heme about an axis defined by the α- and γ-meso carbons.

Cytochrome b5 in some biochemical reactions

EC 1.6.2.2 cytochrome-b5 reductase

NADH + H+ + 2 ferricytochrome b5 → NAD+ + 2 ferrocytochrome b5

EC 1.10.2.1 L-ascorbate—cytochrome-b5 reductase

L-ascorbate + ferricytochrome b5 → monodehydroascorbate + ferrocytochrome b5

EC 1.14.18.2 CMP-N-acetylneuraminate monooxygenase

CMP-N-acetylneuraminate + 2 ferrocytochrome b5 + O2 + 2 H+ → CMP-N-glycoloylneuraminate + 2 ferricytochrome b5 + H2O

EC 1.14.19.1 stearoyl-CoA 9-desaturase

stearoyl-CoA + 2 ferrocytochrome b5 + O2 + 2 H+ → oleoyl-CoA + 2 ferricytochrome b5 + H2O

EC 1.14.19.3 linoleoyl-CoA 9-desaturase

linoleoyl-CoA + 2 ferrocytochrome b5 + O2 + 2 H+ → γ-linolenoyl-CoA + 2 ferricytochrome b5 + H2O

See also

References

  • Lederer F (1994). "The cytochrome b5-fold: an adaptable module". Biochimie. 76 (7): 674–92. doi:10.1016/0300-9084(94)90144-9. PMID 7893819.
  • Napier JA, Michaelson LV, Sayanova O (February 2003). "The role of cytochrome b5 fusion desaturases in the synthesis of polyunsaturated fatty acids". Prostaglandins, Leukotrienes, and Essential Fatty Acids. 68 (2): 135–43. doi:10.1016/S0952-3278(02)00263-6. PMID 12538077.
  • Rivera M, Barillas-Mury C, Christensen KA, Little JW, Wells MA, Walker FA (December 1992). "Gene synthesis, bacterial expression, and 1H NMR spectroscopic studies of the rat outer mitochondrial membrane cytochrome b5". Biochemistry. 31 (48): 12233–40. doi:10.1021/bi00163a037. PMID 1333795.
  • Schenkman JB, Jansson I (February 2003). "The many roles of cytochrome b5". Pharmacology & Therapeutics. 97 (2): 139–52. doi:10.1016/S0163-7258(02)00327-3. PMID 12559387.

External links

  • PDB: 1B5A​ – Solution structure of rat cytochrome b5 (form A)
  • PDB: 1B5B​ – Solution structure of rat cytochrome b5 (form B)
  • PDB: 1CXY​ – X-ray structure of cytochrome b558 from Ectothiorhodospira vacuolata
  • Online Mendelian Inheritance in Man (OMIM) 250790 – Methemoglobinemia due to deficiency of cytochrome b5
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