Cytochrome b5, type A explained

Cytochrome b5, form A (gene name CYB5A), is a human microsomal cytochrome b5.^[1]

Cytochrome b5 is a membrane bound hemoprotein which functions as an electron carrier for several membrane bound oxygenases. It has two isoforms produced by alternative splicing. Isoform 1 is bound to the cytoplasmic side of the endoplasmic reticulum. It has a C-terminal transmembrane alpha-helix. Isoform 2 was found in cytoplasm. Defects in CYB5A are the cause of type IV hereditary methemoglobinemia.

Further reading

• Ng S, Smith MB, Smith HT, Millett F . Effect of modification of individual cytochrome c lysines on the reaction with cytochrome b5. . Biochemistry . 16 . 23 . 4975–8 . 1977 . 199233 . 10.1021/bi00642a006 .
• Dailey HA, Strittmatter P . Modification and identification of cytochrome b5 carboxyl groups involved in protein-protein interaction with cytochrome b5 reductase. . J. Biol. Chem. . 254 . 12 . 5388–96 . 1979 . 10.1016/S0021-9258(18)50608-6 . 221468 . free .
• Mitoma J, Ito A . The carboxy-terminal 10 amino acid residues of cytochrome b5 are necessary for its targeting to the endoplasmic reticulum. . EMBO J. . 11 . 11 . 4197–203 . 1992 . 1396600 . 10.1002/j.1460-2075.1992.tb05513.x. 556930 .
• Giordano SJ, Steggles AW . The human liver and reticulocyte cytochrome b5 mRNAs are products from a single gene. . Biochem. Biophys. Res. Commun. . 178 . 1 . 38–44 . 1991 . 1712589 . 10.1016/0006-291X(91)91776-9 .
• Shephard EA, Povey S, Spurr NK, Phillips IR . Chromosomal localization of a cytochrome b5 gene to human chromosome 18 and a cytochrome b5 pseudogene to the X chromosome. . Genomics . 11 . 2 . 302–8 . 1992 . 1840560 . 10.1016/0888-7543(91)90136-3 .
• Strittmatter P, Hackett CS, Korza G, Ozols J . Characterization of the covalent cross-links of the active sites of amidinated cytochrome b5 and NADH:cytochrome b5 reductase. . J. Biol. Chem. . 265 . 35 . 21709–13 . 1991 . 10.1016/S0021-9258(18)45798-5 . 2123873 . free .
• Ozols J . Structure of cytochrome b5 and its topology in the microsomal membrane. . Biochim. Biophys. Acta . 997 . 1–2 . 121–30 . 1989 . 2752049 . 10.1016/0167-4838(89)90143-X .
• Yoo M, Steggles AW . The complete nucleotide sequence of human liver cytochrome b5 mRNA. . Biochem. Biophys. Res. Commun. . 156 . 1 . 576–80 . 1988 . 3178851 . 10.1016/S0006-291X(88)80881-7 .
• Hegesh E, Hegesh J, Kaftory A . Congenital methemoglobinemia with a deficiency of cytochrome b5. . N. Engl. J. Med. . 314 . 12 . 757–61 . 1986 . 3951505 . 10.1056/NEJM198603203141206 .
• Abe K, Kimura S, Kizawa R . Amino acid sequences of cytochrome b5 from human, porcine, and bovine erythrocytes and comparison with liver microsomal cytochrome b5. . J. Biochem. . 97 . 6 . 1659–68 . 1985 . 4030743 . 10.1093/oxfordjournals.jbchem.a135224. etal.
• Strittmatter P, Spatz L, Corcoran D . Purification and properties of rat liver microsomal stearyl coenzyme A desaturase. . Proc. Natl. Acad. Sci. U.S.A. . 71 . 11 . 4565–9 . 1975 . 4373719 . 10.1073/pnas.71.11.4565 . 433928 . etal. free .
• Rashid MA, Hagihara B, Kobayashi M . Structural studies of cytochrome b5. 3. Sequential studies on human liver cytochrome b5. . J. Biochem. . 74 . 5 . 985–1002 . 1974 . 4770377 . etal.
• Nóbrega FG, Ozols J . Amino acid sequences of tryptic peptides of cytochromes b5 from microsomes of human, monkey, porcine, and chicken liver. . J. Biol. Chem. . 246 . 6 . 1706–17 . 1971 . 10.1016/S0021-9258(18)62368-3 . 4993957 . free .
• Ozols J . Cytochrome b 5 from a normal human liver. Isolation and the partial amino acid sequence. . J. Biol. Chem. . 247 . 7 . 2242–5 . 1972 . 10.1016/S0021-9258(19)45520-8 . 5062820 . free .
• Dailey HA, Strittmatter P . Characterization of the interaction of amphipathic cytochrome b5 with stearyl coenzyme A desaturase and NADPH:cytochrome P-450 reductase. . J. Biol. Chem. . 255 . 11 . 5184–9 . 1980 . 10.1016/S0021-9258(19)70768-6 . 6102994 . free .
• De Silvestris M, D'Arrigo A, Borgese N . The targeting information of the mitochondrial outer membrane isoform of cytochrome b5 is contained within the carboxyl-terminal region. . FEBS Lett. . 370 . 1–2 . 69–74 . 1995 . 7649306 . 10.1016/0014-5793(95)00797-D . 26031756 . free .
• Li XR, Giordano SJ, Yoo M, Steggles AW . The isolation and characterization of the human cytochrome b5 gene. . Biochem. Biophys. Res. Commun. . 209 . 3 . 894–900 . 1995 . 7733981 . 10.1006/bbrc.1995.1582 .
• Giordano SJ, Yoo M, Ward DC . The human cytochrome b5 gene and two of its pseudogenes are located on chromosomes 18q23, 14q31-32.1 and 20p11.2, respectively. . Hum. Genet. . 92 . 6 . 615–8 . 1994 . 8262522 . 10.1007/BF00420948 . 28828499 . etal. free .
• Guengerich FP, Johnson WW . Kinetics of ferric cytochrome P450 reduction by NADPH-cytochrome P450 reductase: rapid reduction in the absence of substrate and variations among cytochrome P450 systems. . Biochemistry . 36 . 48 . 14741–50 . 1998 . 9398194 . 10.1021/bi9719399 .
• Lee-Robichaud P, Akhtar ME, Akhtar M . Control of androgen biosynthesis in the human through the interaction of Arg347 and Arg358 of CYP17 with cytochrome b5. . 332 . Biochem. J. . (Pt 2) . 2. 293–6 . 1998 . 9601054 . 10.1042/bj3320293. 1219480 .

Notes and References

1. Web site: Entrez Gene: CYB5A Cytochrome b5, form A.