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Gene Review

CYB5A  -  cytochrome b5 type A (microsomal)

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Disease relevance of CYB5

  • The amino acid sequences of cytochrome P-450CAM and putidaredoxin of the camphor hydroxylase [camphor, reduced-putida-ferredoxin:oxygen oxidoreductase (5-hydroxylating), EC] of Pseudomonas putida are compared to each other and then to the sequences of bovine adrenodoxin and cytochrome b5 [1].
  • To achieve these aims, 13C-labeled heme OM cytochrome b5 was expressed in Escherichia coli as previously described [Rivera M., Walker, F.A. (1995) Anal. Biochem. 230, 295-302] [2].

High impact information on CYB5


Biological context of CYB5


Anatomical context of CYB5


Associations of CYB5 with chemical compounds

  • Conserved phenylalanine 35 is one of the hydrophobic patch residues on the surface of cytochrome b5 (cyt b5) [14].
  • However, residue 97 (C-terminal residue) was proline for human erythrocyte cytochrome b5 and serine for the porcine protein, while residues 97 (joint region) of human and porcine liver cytochromes b5 were threonine [9].
  • As in the rat species, cytochrome b5 preparations from man, rabbit, calf and horse had an acetylated alanine as the first residue [11].
  • The proximal histidine of the globins and two adjacent helices are equivalent to the sixth iron ligand and adjacent helices of cytochrome b5 [15].
  • Chemical modification of the four carboxyl groups of the nonpolar peptide of cytochrome b5 with carbodiimide and methylamine to produce a derivative with no anionic charged residues also resulted in a loss of this type of stable membrane interaction [16].

Physical interactions of CYB5

  • 13C NMR spectroscopic and X-ray crystallographic study of the role played by mitochondrial cytochrome b5 heme propionates in the electrostatic binding to cytochrome c [2].

Enzymatic interactions of CYB5


Other interactions of CYB5


Analytical, diagnostic and therapeutic context of CYB5

  • The conformation for cytochrome b5 determined in this study reveals several small, but significant, differences in structure to that determined previously by crystallography for a smaller fragment of this protein [7].
  • The existence of a metMb-ferrous cytochrome b5 complex is demonstrated by mutual perturbation of the proteins' respective electrophoretic titration curves between pH 4 and 7 [12].
  • The binding is complete as indicated by density gradient centrifugation and is accompanied by approximately a 2-fold increase in the fluorescence emission of the protein, and insertion in the bilayer is apparently in an orientation indistinguishable from that of the whole cytochrome b5 molecule [20].
  • Neutron diffraction analysis of cytochrome b5 reconstituted in deuterated lipid multilayers [21].
  • The structure and stability of cytochrome b5 reconstituted with manganese protoporphyrin IX instead of iron protoporphyrin IX has been investigated by resonance Raman spectroscopy and stopped-flow visible spectroscopy [22].


  1. Camphor hydroxylase of Pseudomonas putida: vestiges of sequence homology in cytochrome P-450CAM, putidaredoxin, and related proteins. Dus, K.M. Proc. Natl. Acad. Sci. U.S.A. (1984) [Pubmed]
  2. 13C NMR spectroscopic and X-ray crystallographic study of the role played by mitochondrial cytochrome b5 heme propionates in the electrostatic binding to cytochrome c. Rodríguez-Marañón, M.J., Qiu, F., Stark, R.E., White, S.P., Zhang, X., Foundling, S.I., Rodríguez, V., Schilling, C.L., Bunce, R.A., Rivera, M. Biochemistry (1996) [Pubmed]
  3. High-level expression in Escherichia coli of enzymatically active fusion proteins containing the domains of mammalian cytochromes P450 and NADPH-P450 reductase flavoprotein. Fisher, C.W., Shet, M.S., Caudle, D.L., Martin-Wixtrom, C.A., Estabrook, R.W. Proc. Natl. Acad. Sci. U.S.A. (1992) [Pubmed]
  4. Mechanisms of integration of de novo-synthesized polypeptides into membranes: signal-recognition particle is required for integration into microsomal membranes of calcium ATPase and of lens MP26 but not of cytochrome b5. Anderson, D.J., Mostov, K.E., Blobel, G. Proc. Natl. Acad. Sci. U.S.A. (1983) [Pubmed]
  5. Evidence that two forms of bovine erythrocyte cytochrome b5 are identical to segments of microsomal cytochrome b5. Douglas, R.H., Hultquist, D.E. Proc. Natl. Acad. Sci. U.S.A. (1978) [Pubmed]
  6. 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. (1995) [Pubmed]
  7. The solution structure of bovine ferricytochrome b5 determined using heteronuclear NMR methods. Muskett, F.W., Kelly, G.P., Whitford, D. J. Mol. Biol. (1996) [Pubmed]
  8. The isolation and characterization of the bovine cytochrome b5 gene, and a transcribed pseudogene. Cristiano, R.J., Giordano, S.J., Steggles, A.W. Genomics (1993) [Pubmed]
  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. (1985) [Pubmed]
  10. Characterization of lysyl residues of NADH-cytochrome b5 reductase implicated in charge-pairing with active-site carboxyl residues of cytochrome b5 by site-directed mutagenesis of an expression vector for the flavoprotein. Strittmatter, P., Kittler, J.M., Coghill, J.E., Ozols, J. J. Biol. Chem. (1992) [Pubmed]
  11. Structure of cytochrome b5 and its topology in the microsomal membrane. Ozols, J. Biochim. Biophys. Acta (1989) [Pubmed]
  12. Myoglobin: cytochrome b5 interactions and the kinetic mechanism of metmyoglobin reductase. Livingston, D.J., McLachlan, S.J., La Mar, G.N., Brown, W.D. J. Biol. Chem. (1985) [Pubmed]
  13. The B-type cytochrome in endoplasmic reticulum of mammary gland epithelium and milk fat globule membranes consists of two components cytochrome b5 and cytochrome P-420. Bruder, G., Fink, A., Jarasch, E.D. Exp. Cell Res. (1978) [Pubmed]
  14. X-ray crystallography, CD and kinetic studies revealed the essence of the abnormal behaviors of the cytochrome b5 Phe35-->Tyr mutant. Yao, P., Wu, J., Wang, Y.H., Sun, B.Y., Xia, Z.X., Huang, Z.X. Eur. J. Biochem. (2002) [Pubmed]
  15. A comparison of the heme binding pocket in globins and cytochrome b5. Rossmann, M.G., Argos, P. J. Biol. Chem. (1975) [Pubmed]
  16. The role of COOH-terminal anionic residues in binding cytochrome b5 to phospholipid vesicles and biological membranes. Dailey, H.A., Strittmatter, P. J. Biol. Chem. (1981) [Pubmed]
  17. Cytochrome P450c17 from porcine and bovine adrenal catalyses the formation of 5,16-androstadien-3 beta-ol from pregnenolone in the presence of cytochrome b5. Meadus, W.J., Mason, J.I., Squires, E.J. J. Steroid Biochem. Mol. Biol. (1993) [Pubmed]
  18. Mapping the binding interface of the cytochrome b5-cytochrome c complex by nuclear magnetic resonance. Shao, W., Im, S.C., Zuiderweg, E.R., Waskell, L. Biochemistry (2003) [Pubmed]
  19. Effect of the hydrophile-lipophile balance of non-ionic detergents (Triton X-series) on the solubilization of biological membranes and their integral b-type cytochromes. Slinde, E., Flatmark, T. Biochim. Biophys. Acta (1976) [Pubmed]
  20. The nonpolar peptide segment of cytochrome b5. Binding to phospholipid vesicles and identification of the fluorescent tryptophanyl residue. Fleming, P.J., Strittmatter, P. J. Biol. Chem. (1978) [Pubmed]
  21. Neutron diffraction analysis of cytochrome b5 reconstituted in deuterated lipid multilayers. Gogol, E.P., Engelman, D.M., Zaccai, G. Biophys. J. (1983) [Pubmed]
  22. Resonance Raman spectral properties and stability of manganese protoporphyrin IX cytochrome b5. Gruenke, L.D., Sun, J., Loehr, T.M., Waskell, L. Biochemistry (1997) [Pubmed]
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