Uncoupling of choline-O-sulphate utilization from osmoprotection in Pseudomonas putida
Uncoupling of choline-O-sulphate utilization from osmoprotection in Pseudomonas putida
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DOI：
10.1111/j.1365-2958.2006.05488.x
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发表时间：
2006-12-01
影响因子：
3.6
通讯作者：
Canovas, David
中科院分区：
文献类型：
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作者：
Calcagno Galvao, Teca;de Lorenzo, Victor;Canovas, David
恶臭假单胞菌KT 2440中用于胆碱-O-硫酸盐（COS）利用的公认的bet基因的基因组背景使得betC（胆碱硫酸酯酶）位于ATP结合盒转运蛋白和LysR型调节剂附近，但远离编码将胆碱转化为甘氨酸甜菜碱的酶的betBA。COS代谢功能的遗传布局的后果已被检查与一套遗传和生化方法。betC缺失的表型揭示了bet编码产物的效用的早期线索。该突变体仍然积累完整的COS，但不能利用该化合物作为碳源或氮源。此外，betC的表达在高盐浓度下下调，表明该基因的主要作用在于COS代谢，而不是在盐保护。与此相反，betBA基因所需的胆碱转化成高效相容的溶质甘氨酸甜菜碱（和随之而来的耐高盐性），也为它的利用作为碳或氮源。因此，与枯草芽孢杆菌和苜蓿中华根瘤菌的情况不同，betC与恶臭假单胞菌中的甜菜碱保护无关，而betBA基因是甜菜碱合成和对高渗透压的耐受性所必需的。
The genomic context of the recognized bet genes for choline-O-sulphate (COS) utilization in Pseudomonas putida KT2440 is such that betC (choline sulphatase) lies adjacent to an ATP-binding cassette transporter and a LysR type regulator, but well away from betBA, encoding enzymes for transformation of choline into glycine betaine. The consequences of such genetic layout of the functions for COS metabolism have been examined with a suite of genetic and biochemical approaches. An early clue of the utilities of the bet-encoded products was exposed by the phenotypes of a betC deletion. This mutant still accumulated intact COS but failed to use this compound as carbon or nitrogen source. Furthermore, betC expression was downregulated at high salt concentrations, showing that the principal role of this gene lied in COS metabolism, not in osmoprotection. In contrast, the betBA genes were required for choline transformation into the highly effective compatible solute glycine betaine (and the concomitant endurance to high salt) and also for its utilization as carbon or nitrogen source. Thus, unlike in the cases of Bacillus subtilis and Sinorhizobium meliloti, betC is unrelated to osmoprotection in Pseudomonas putida while the betBA genes are required for both betaine synthesis and tolerance to high osmotic pressure.