Yamashita M, Azakami H, Yokoro N, Roh J H, Suzuki H, Kumagai H, Murooka Y
Department of Biotechnology, Graduate School of Engineering, Osaka University, Japan.
J Bacteriol. 1996 May;178(10):2941-7. doi: 10.1128/jb.178.10.2941-2947.1996.
The structural gene for copper- and topa quinone-containing monoamine oxidase (maoA) and an unknown amine oxidase gene have been located at 30.9 min on the Escherichia coli chromosome. Deletion analysis showed that the unknown gene was located within a 1.1-kb cloned fragment adjacent to the maoA gene. The nucleotide sequence of this fragment was determined, and a single open reading frame (maoB) consisting of 903 bp was found. The gene encoded a polypeptide with a predicted molecular mass of 34,619 Da which was correlated with the migration on a sodium dodecyl sulfate-polyacrylamide gel. The predicted amino acid sequence of the MaoB protein was identical to the NH2-terminal amino acid sequence derived by Edman degradation of the protein synthesized under the self-promoter. No homology of the nucleotide sequence of maoB to the sequences of any reported genes was found. However, the amino acid sequence of MaoB showed a high level of homology with respect to the helix-turn-helix motif of the AraC family in its C terminus. The homology search and disruption of maoA on the chromosome led to the conclusion that MaoB is a transcriptional activator of maoA but not an amine oxidase. The consensus sequence of the cyclic AMP-cyclic AMP receptor protein complex binding domain was adjacent to the putative promoter for the maoB gene. By use of lac gene fusions with the maoA and maoB genes, we showed that the maoA gene is regulated by tyramine and MaoB and that the expression of the maoB gene is subject to catabolite repression. Thus, it seems likely that tyramine and the MaoB protein activate the transcription of maoA by binding to the regulatory region of the maoA gene.
含铜和topa醌的单胺氧化酶（maoA）的结构基因以及一个未知的胺氧化酶基因位于大肠杆菌染色体的30.9分钟处。缺失分析表明，该未知基因位于与maoA基因相邻的一个1.1 kb克隆片段内。测定了该片段的核苷酸序列，发现一个由903 bp组成的单一开放阅读框（maoB）。该基因编码一种预测分子量为34,619 Da的多肽，这与在十二烷基硫酸钠 - 聚丙烯酰胺凝胶上的迁移情况相关。MaoB蛋白的预测氨基酸序列与通过对在自身启动子下合成的蛋白质进行埃德曼降解得到的NH2末端氨基酸序列相同。未发现maoB的核苷酸序列与任何已报道基因的序列有同源性。然而，MaoB的氨基酸序列在其C末端与AraC家族的螺旋 - 转角 - 螺旋基序具有高度同源性。对染色体上maoA的同源性搜索和破坏导致得出结论：MaoB是maoA的转录激活因子而非胺氧化酶。环腺苷酸 - 环腺苷酸受体蛋白复合物结合结构域的共有序列与maoB基因的推定启动子相邻。通过使用与maoA和maoB基因的lac基因融合，我们表明maoA基因受酪胺和MaoB调控，且maoB基因的表达受分解代谢物阻遏。因此，酪胺和MaoB蛋白似乎可能通过与maoA基因的调控区域结合来激活maoA的转录。
