Structure and regulation of the omega-3 polyunsaturated fatty acid synthase genes from the deep-sea bacterium Photobacterium profundum strain SS9
Structure and regulation of the omega-3 polyunsaturated fatty acid synthase genes from the deep-sea bacterium Photobacterium profundum strain SS9
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DOI：
10.1099/00221287-148-6-1903
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发表时间：
2002-06-01
期刊：
影响因子：
2.8
通讯作者：
Bartlett, DH
中科院分区：
文献类型：
--
作者：
Allen, EE;Bartlett, DH
欧米茄-3多不饱和脂肪酸（PUFA）如二十碳五烯酸（20：5 n-3; EPA）和二十二碳六烯酸（22：6 n-3; DHA）已被证明在促进心血管健康、适当的人类发育和预防某些癌症方面具有重要意义。来自低温和高压海洋环境的高比例细菌分离物产生EPA或DHA。本文介绍了一个33 kbp的基因座的深海细菌发光杆菌菌株SS 9，其中包括EPA生物合成所需的五个基因中的四个。与其他细菌pfa（多不饱和脂肪酸）基因，推导的氨基酸序列编码的SS 9基因揭示大的多结构域蛋白，可能催化EPA生物合成的一种新的聚酮合成机制。RNA酶保护实验将SS 9 pfa基因分成两个转录单位pfaA-C和pfaD。鉴定了pfaA转录起始位点。培养在提高静水压力或降低温度没有增加pfa基因的表达，尽管在这些条件下，EPA的百分比组合物的增加。然而，一种调节突变体的特征在于其表现出pfaA-D的表达增加和EPA组成百分比升高。这一结果表明，存在一个调节因子，协调pfaA-D转录。关于PUFA合成所需的活动的额外考虑与细菌pfa基因和基因产物的比较分析一起提供。
Omega-3 polyunsaturated fatty acids (PUFAs) such as eicosapentaenoic acid (20:5n-3; EPA) and docosahexaenoic acid (22:6n-3; DHA) have been shown to be of major importance in the promotion of cardiovascular health, proper human development and the prevention of some cancers. A high proportion of bacterial isolates from low-temperature and high-pressure marine environments produce EPA or DHA. This paper presents the sequence of a 33 kbp locus from the deep-sea bacterium Photobacterium profundum strain SS9 which includes four of the five genes required for EPA biosynthesis. As with other bacterial pfa (polyunsaturated fatty acid) genes, the deduced amino acid sequences encoded by the SS9 genes reveal large multidomain proteins that are likely to catalyse EPA biosynthesis by a novel polyketide synthesis mechanism. RNase protection experiments separated the SS9 pfa genes into two transcriptional units, pfaA-C and pfaD. The pfaA transcriptional start site was identified. Cultivation at elevated hydrostatic pressure or reduced temperature did not increase pfa gene expression despite the resulting increase in percentage composition of EPA under these conditions. However, a regulatory mutant was characterized which showed both increased expression of pfaA-D and elevated EPA percentage composition. This result suggests that a regulatory factor exists which coordinates pfaA-D transcription. Additional consideration regarding the activities required for PUFA synthesis is provided together with comparative analyses of bacterial pfa genes and gene products.