Genes for the synthesis of the osmoprotectant glycine betaine from choline in the moderately halophilic bacterium Halomonas elongata DSM 3043
Genes for the synthesis of the osmoprotectant glycine betaine from choline in the moderately halophilic bacterium Halomonas elongata DSM 3043
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DOI：
10.1099/00221287-146-2-455
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发表时间：
2000-02-01
期刊：
影响因子：
2.8
通讯作者：
Nieto, JJ
中科院分区：
文献类型：
--
作者：
Cánovas, D;Vargas, C;Nieto, JJ
通过对甘氨酸甜菜碱合成缺陷的大肠杆菌菌株进行功能互补，分离出中度嗜盐菌延长长盐单胞菌 DSM 3043 中参与胆碱氧化途径至甘氨酸甜菜碱的基因。克隆的区域能够介导大肠杆菌中胆碱氧化为甘氨酸甜菜碱，但不能介导胆碱的转运，这表明参与胆碱转运的基因不与甘氨酸甜菜碱合成基因聚集在一起。对克隆 DNA 的 4.6 kb 片段进行的核苷酸序列分析揭示了三个 ORF (betIBA) 的出现，这三个 ORF 明显排列在操纵子中。推导的 betI 基因产物表现出 DNA 结合调节蛋白的典型特征。推导的 Bets 和 BetA 蛋白分别与多种生物体的可溶性甘氨酸甜菜碱醛脱氢酶和膜结合胆碱脱氢酶表现出显着的相似性。有证据表明 BetA 能够氧化胆碱和甘氨酸甜菜碱醛，因此可以介导甘氨酸甜菜碱合成中的两个步骤。
The genes involved in the oxidative pathway of choline to glycine betaine in the moderate halophile Halomonas elongata DSM 3043 were isolated by functional complementation of an Escherichia coli strain defective in glycine betaine synthesis. The cloned region was able to mediate the oxidation of choline to glycine betaine in E. coli, but not the transport of choline, indicating that the gene(s) involved in choline transport are not clustered with the glycine betaine synthesis genes. Nucleotide sequence analysis of a 4.6 kb segment from the cloned DNA revealed the occurrence of three ORFs (betIBA) apparently arranged in an operon. The deduced betI gene product exhibited features typical for DNA-binding regulatory proteins. The deduced Bets and BetA proteins showed significant similarity to soluble glycine betaine aldehyde dehydrogenases and membrane-bound choline dehydrogenases, respectively, from a variety of organisms. Evidence is presented that BetA is able to oxidize both choline and glycine betaine aldehyde and therefore can mediate both steps in the synthesis of glycine betaine.