A NEW OXYGEN-REGULATED OPERON IN ESCHERICHIA-COLI COMPRISES THE GENES FOR A PUTATIVE 3RD CYTOCHROME-OXIDASE AND FOR PH 2.5 ACID-PHOSPHATASE (APPA)
A NEW OXYGEN-REGULATED OPERON IN ESCHERICHIA-COLI COMPRISES THE GENES FOR A PUTATIVE 3RD CYTOCHROME-OXIDASE AND FOR PH 2.5 ACID-PHOSPHATASE (APPA)
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DOI：
10.1007/bf00267454
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发表时间：
1991-10-01
期刊：
影响因子：
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通讯作者：
BOQUET, PL
中科院分区：
文献类型：
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作者：
DASSA, J;FSIHI, H;BOQUET, PL
大肠杆菌酸性磷酸酶基因AppA是在缺氧条件下表达的，并受AppR产物(Katf)的正调控，该产物编码一种新的Sigma转录启动因子。然而，AppA从其最近的启动子(P1)的转录不能解释总的pH 2.5酸性磷酸酶的表达，并且不受调控。通过插入转座子TnPhoA和与LacZ融合，对APPA上游的克隆区进行延伸和分析。它包含两个新基因appC和appB，这两个基因都编码胞外蛋白。APPC和AppB由APPC上游的启动子(P2)表达。这两个基因和AppA一样，都受氧和AppR基因产物的调控，就像之前对AppA所显示的那样。对核苷酸序列和转录起源的分析已经证实，P2-APPC-AppB-(ORFX)-P1-AppA区域是以操纵子的形式组织在染色体上的，该操纵子从P2顺时针转录而来，并且P1是单独的AppA的次要启动子。AppC和appB基因分别编码M(R)58133和42377的蛋白，具有完整膜蛋白的特征。APPC和AppB的推导氨基酸序列分别与大肠杆菌细胞色素d氧化酶亚基I和II有60%和57%的同源性(由cydA和cydB基因编码)。APPC和AppB蛋白构成了一个新的细胞色素氧化酶或新的氧解毒系统，这一观点得到了以下观察的支持：缺失这三个基因的突变体对氧的敏感性比CyO(细胞色素o氧化酶)、Cyd(细胞色素d氧化酶)和appB都缺失的突变体对氧的敏感性更高。
The Escherichia coli acid phosphatase gene appA is expressed in response to oxygen deprivation and is positively controlled by the product of appR (katF) which encodes a putative new sigma-transcription-initiation factor. However, transcription of appA from its nearest promoter (P1) did not account for total pH 2.5 acid phosphatase expression and was not subject to regulation. The cloned region upstream of appA was extended nd analyzed by insertions of transposon TnphoA and by fusions with lacZ. It contains two new genes, appC and appB, which both encode extracytoplasmic proteins. appC and appB are expressed from a promoter (P2) lying just upstream of appC. Both genes are regulated by oxygen, as is appA, and by appR gene product exactly as previously shown for appA. Analysis of the nucleotide sequence and of the origins of transcription have confirmed that the P2-appC-appB- (ORFX)-P1-appA region is organized on the chromosome as an operon transcribed clockwise from P2 and that P1 is a minor promoter for appA alone. Genes appC and appB encode proteins of M(r) 58133 and 42377, respectively, which have the characteristics of integral membrane proteins. The deduced amino acid sequences of appC and appB show 60% and 57% homology, respectively, with subunits I and II of the E. coli cytochrome d oxidase (encoded by genes cydA and cydB). The notion that the AppC and AppB proteins constitute a new cytochrome oxidase or a new oxygen-detoxifying system is supported by the observation of enhanced sensitivity to oxygen of mutants lacking all three genes, cyo (cytochrome o oxidase), cyd (cytochrome d oxidase) and appB, compared to that of cyo cyd double mutants.