Regulation of gene expression and function of cytochrome b5

在这些研究中，我们研究了细胞色素b5.1基因表达和功能的调节。鱼鼻水已成功地从被毛类中克隆了2个cDNA。结果表明，其中一个基因的编码区为1.8kbp，编码135个氨基酸；另一个基因的编码区为790bp，编码134个氨基酸。这两个氨基酸序列与哺乳动物细胞计时酶b5s2的氨基酸序列有75%的同源性。Steggles还克隆了猪细胞色素B的cDNA，该基因在第96个密码子后插入24bp，编码G1u97、Pro98和stop99，产生可溶性的细胞色素b5。可溶性和膜结合型基因表达的调控依赖于启动子的功能。Porter构建了细胞色素b5、P450和P450还原酶在大肠杆菌中的共表达系统。细胞色素b5通过细胞色素P450/P450还原酶系统有效促进药物代谢。坎贝尔研究了细胞色素b5部分在硝酸还原酶中的作用。硝酸还原酶的细胞色素b5和黄素蛋白结构域以融合蛋白的形式表达并结晶。在结晶结构的基础上，他通过定点突变成功地将依赖NADPH的酶转变为NADH特异的酶。

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.