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首页> 外文期刊>Journal of bacteriology >Molecular analysis of the gat genes from Escherichia coli and of their roles in galactitol transport and metabolism.
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Molecular analysis of the gat genes from Escherichia coli and of their roles in galactitol transport and metabolism.

机译：大肠杆菌中gat基因的分子分析及其在半乳糖醇运输和代谢中的作用。

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In enteric bacteria, the hexitol galactitol (Gat) (formerly dulcitol) is taken up through enzyme II (II(Gat)) of the phosphoenolpyruvate-dependent phosphotransferase system (PTS), and accumulated as galactitol 1-phosphate (Gat1P). The gat genes involved in galactitol metabolism have been isolated from the wild-type isolate Escherichia coli EC3132 and cloned on a 7.8-kbp PstI DNA fragment. They comprise six complete open reading frames and one truncated open reading frame in the order gatYZABCDR'. The genes gatABC code for the proteins GatA (150 residues) and GatB (94 residues), which correspond to the hydrophilic domains IIA(Gat) and IIB(Gat), and GatC, which represents a membrane-bound transporter domain IIC(Gat) (35 kDa, 427 residues). The three polypeptides together constitute a II(Gat) of average size (671 residues). Gene gatD codes for a Gat1P-specific NAD-dependent dehydrogenase (38 kDa, 346 residues), gatZ codes for a protein (42 kDa, 378 residues) of unknown function, and gatY (31 kDa, 286 residues) codes for a D-tagatose-1,6-bisphosphate aldolase with similarity to other known ketose-bisphosphate aldolases. The truncated gatR' gene, whose product shows similarity to the glucitol repressor GutR, closely resembles a gatR gene fragment from E. coli K-12. The gat genes map in both organisms at similar positions, in E. coli K-12, where they are transcribed counterclockwise at precisely 46.7 min or 2,173 to 2,180 kbp. The genes are expressed constitutively in both strains, probably due to a mutation(s) in gatR. Transcription initiation sites for the gatYp and the gatRp promoters were determined by primer extension analysis.
机译：在肠细菌中，己糖醇半乳糖（Gat）（以前称为二甘醇）通过磷酸烯醇丙酮酸依赖性磷酸转移酶系统（PTS）的酶II（II（Gat））吸收，并以半乳糖1-磷酸（Gat1P）的形式积累。已从野生型分离株大肠杆菌EC3132中分离出涉及半乳糖醇代谢的gat基因，并将其克隆到7.8-kbp PstI DNA片段上。它们按gatYZABCDR'顺序包含6个完整的开放阅读框和1个截短的开放阅读框。 gatABC基因编码蛋白质GatA（150个残基）和GatB（94个残基），分别对应于亲水性结构域IIA（Gat）和IIB（Gat），以及GatC，其代表膜结合转运蛋白结构域IIC（Gat） （35 kDa，427个残基）。这三种多肽共同构成平均大小的II（Gat）（671个残基）。基因gatD编码Gat1P特异的NAD依赖性脱氢酶（38 kDa，346个残基），gatZ编码功能未知的蛋白质（42 kDa，378个残基），而gatY（31 kDa，286个残基）编码D- tagatose-1,6-bisphosphate aldolase与其他已知的ketose-bisphosphate aldolases具有相似性。截短的gatR'基因的产物与葡萄糖醇阻遏物GutR相似，它与大肠杆菌K-12的gatR基因片段极为相似。 gat基因在大肠杆菌K-12中处于相似位置的两种生物中定位，在精确的46.7分钟或2,173至2,180 kbp处逆时针转录。基因可能在两种菌株中组成型表达，可能是由于gatR中的突变所致。通过引物延伸分析确定了gatYp和gatRp启动子的转录起始位点。

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