Regulation of gene expression and function of cytochrome b5

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In these studies we investigated the regulation of gene expression and function of cytochrome b5.1. Yubisui has succeeded in cloning 2 cDNAs from tunicates. One of them obtained from Polyandrocarpa misakiensis has about 1.8 kbp including the coding regions of 405 bp for 135 amino acids, and the other from Ciona savignyi has about 790 bps including the coding region of 402 bp for 134 amino acids. Both amino acid sequences have about 75% homology to those of mammalian cytochronie b5s.2. Steggles also cloned a cDNA for swine cytochrome bS, which contained a 24 bp insertion after 96th codon to code for G1u97, Pro98 and stop99 to produce the soluble form of cytochrome b5. Regulation of gene expression of the soluble and membrane-bound form depends on the functin of promotors.3. Porter constructed a co-expression system for cytochrome b5, P450, and P450 reductase in Eschericlzia coli. Cytochrome b5 effectively accerelated the drug metabolism by cytochrome P450/P450 reductase system.4. Campbell investigated the function of cytochrome b5 moiety in nitrate reductase. The cytochrome b5 and flavoprotein domains of the nitrate reductase were expressed as a fusion protein, and crystalyzed. Based on the crystalyzed structure he succeeded in changing the NADPH-dependent enzyme to NADH-specific enzyme by site-directed mutagenesis.