GENETIC-ANALYSIS OF THE DTDP-RHAMNOSE BIOSYNTHESIS REGION OF THE ESCHERICHIA-COLI VW187 (O7/K1) RFB GENE-CLUSTER - IDENTIFICATION OF FUNCTIONAL HOMOLOGS OF RFBB AND RFBA IN THE RFF CLUSTER AND CORRECT LOCATION OF THE RFFE GENE
GENETIC-ANALYSIS OF THE DTDP-RHAMNOSE BIOSYNTHESIS REGION OF THE ESCHERICHIA-COLI VW187 (O7/K1) RFB GENE-CLUSTER - IDENTIFICATION OF FUNCTIONAL HOMOLOGS OF RFBB AND RFBA IN THE RFF CLUSTER AND CORRECT LOCATION OF THE RFFE GENE
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DOI：
10.1128/jb.177.19.5539-5546.1995
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发表时间：
1995-10-01
影响因子：
3.2
通讯作者：
VALVANO, MA
中科院分区：
文献类型：
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作者：
MAROLDA, CL;VALVANO, MA
大肠杆菌O7特异性脂多糖的o重复单元由半乳糖、甘露糖、鼠李糖、4-乙酰氨基-4,6-二脱氧葡萄糖和n -乙酰氨基葡萄糖组成。我们最近表征了参与糖前体gdp -甘露糖生物合成的基因，这些基因发生在大肠杆菌O7:K1菌株VW187 （C， L,）中。Marolda和M. A. Valvano， J.细菌学杂志，1993)，本研究鉴定了鼠李糖另一前体dtdp -鼠李糖编码酶的rfbBDAC基因并对其进行了测序。这些基因位于rfb（EcO7）区域的上游，与各种肠道和非肠道细菌中发现的类似基因相比，它们具有很强的保守性。在rfbB的上游，我们发现了一个包含rfb启动子的DNA片段和一个高度保守的未翻译先导序列，该序列也存在于其他表面多糖基因簇的启动子区域。此外，我们还确定了rfbB和rfbA的同源物rffG （o355）和rffH （o292）分别位于rff簇上，参与肠杆菌共同抗原的合成。我们提供了生化证据，证明rffG和rffH分别编码dtdp -葡萄糖脱水酶和葡萄糖- 1磷酸胸苷基转移酶活性，并且我们还发现rffG补充了O7(+) cosmid pJHCV32中的rfbB缺陷，我们还证明了rffG与rffE不同，并将rffE基因定位到rff簇的第二个基因上。
The O-repeating unit of the Escherichia coli O7-specific lipopolysaccharide is made of galactose, mannose, rhamnose, 4-acetamido-4,6-dideoxyglucose, and N-acetylglucosamine, We have recently characterized the genes involved in the biosynthesis of the sugar precursor GDP-mannose occurring in the E. coli O7:K1 strain VW187 (C, L,. Marolda and M. A. Valvano, J. Bacteriol. 175:148-158, 1993), In the present study, we identified and sequenced the rfbBDAC genes encoding the enzymes for the biosynthesis of another precursor, dTDP-rhamnose. These genes are localized on the upstream end of the rfb(EcO7) region, and they are strongly conserved compared with similar genes found in various enteric and nonenteric bacteria. Upstream of rfbB we identified a DNA segment containing the rfb promoter and a highly conserved untranslated leader sequence also present in the promoter regions of other surface polysaccharide gene clusters, Also, we have determined that rfbB and rfbA have homologs, rffG (o355) and rffH (o292), respectively, located on the rff cluster, which is involved in the synthesis of enterobacterial common antigen, We provide biochemical evidence that rffG and rffH encode dTDP-glucose dehydratase and glucose-l phosphate thymidylyltransferase activities, respectively, and we also show that rffG complemented the rfbB defect in the O7(+) cosmid pJHCV32, We also demonstrate that rffG is distinct from rffE and map the rffE gene to the second gene of the rff cluster.