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的基因表达和功能的调节。Yubisui成功地从被囊动物中克隆了2个cDNA。其中一个从Misakiensis中获得的片段长度约为1.8kbp，包括405 bp的135个氨基酸的编码区，另一个从Ciona savignyi中获得的片段长度约为790 bp，包括402 bp的134个氨基酸的编码区。这两个氨基酸序列与哺乳动物细胞周期b5 s的氨基酸序列具有约75%的同源性。Steggles还克隆了猪细胞色素bS的cDNA，该cDNA在第96位密码子后插入24 bp，编码G1 u97、Pro 98和stop 99，以产生可溶形式的细胞色素b5。可溶性和膜结合形式的基因表达调控依赖于启动子的功能. Porter在大肠杆菌中构建了细胞色素b5、P450和P450还原酶的共表达系统。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.坎贝尔研究了硝酸还原酶中细胞色素b5部分的功能。硝酸还原酶的细胞色素b5和黄素蛋白结构域表达为融合蛋白，并结晶。基于晶体结构，他成功地通过定点突变将NADPH依赖性酶改变为NADH特异性酶。

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.