Dong Huijuan, Wang Haihong, Cronan John E
Department of Microbiology, University of Illinois at Urbana-Champaign, Urbana, Illinois, USA.
College of Life Sciences, South China Agricultural University, Guangzhou, China.
Mol Microbiol. 2023 Feb;119(2):252-261. doi: 10.1111/mmi.15018. Epub 2023 Jan 16.
The genomes of the best-studied pseudomonads, Pseudomonas aeruginosa and Pseudomonas putida, which share 85% of the predicted coding regions, contain a fabA fabB operon (demonstrated in P. aeruginosa, putative in P. putida). The enzymes encoded by the fabA and fabB genes catalyze the introduction of a double bond into a 10-carbon precursor which is elongated to the 16:1Δ9 and 18:1Δ11 unsaturated fatty acyl chains required for functional membrane phospholipids. A detailed analysis of transcription of the P. putida fabA fabB gene cluster showed that fabA and fabB constitute an operon and disclosed an unexpected and essential fabB promoter located within the fabA coding sequence. Inactivation of the fabA fabB operon fails to halt the growth of P. aeruginosa PAO1 but blocks growth of P. putida F1 unless an exogenous unsaturated fatty acid is provided. We report that the asymmetry between these two species is due to the P. aeruginosa PAO1 desA gene which encodes a fatty acid desaturase that introduces double bonds into the 16-carbon acyl chains of membrane phospholipids. Although P. putida F1 encodes a putative DesA homolog that is 84% identical to the P. aeruginosa PAO1, the protein fails to provide sufficient unsaturated fatty acid synthesis for growth when the FabA FabB pathway is inactivated. We report that the P. putida F1 DesA homolog can functionally replace the P. aeruginosa DesA. Hence, the defect in P. putida F1 desaturation is not due to a defective P. putida F1 DesA protein but probably to a weakly active component of the electron transfer process.
研究最为深入的假单胞菌属细菌，即铜绿假单胞菌和恶臭假单胞菌，其基因组共享85%的预测编码区域，包含一个fabA fabB操纵子（在铜绿假单胞菌中得到证实，在恶臭假单胞菌中为推测存在）。fabA和fabB基因编码的酶催化将一个双键引入到一个10碳前体中，该前体随后延伸为功能性膜磷脂所需的16:1Δ9和18:1Δ11不饱和脂肪酰链。对恶臭假单胞菌fabA fabB基因簇转录的详细分析表明，fabA和fabB构成一个操纵子，并揭示了一个位于fabA编码序列内的意外且必需的fabB启动子。fabA fabB操纵子的失活未能阻止铜绿假单胞菌PAO1的生长，但会阻止恶臭假单胞菌F1的生长，除非提供外源不饱和脂肪酸。我们报道，这两个物种之间的不对称性是由于铜绿假单胞菌PAO1的desA基因，该基因编码一种脂肪酸去饱和酶，可将双键引入膜磷脂的16碳酰链中。尽管恶臭假单胞菌F1编码一个与铜绿假单胞菌PAO1的DesA同源性为84%的推测蛋白，但当FabA FabB途径失活时，该蛋白无法提供足够的不饱和脂肪酸合成以支持生长。我们报道，恶臭假单胞菌F1的DesA同源物可以在功能上替代铜绿假单胞菌的DesA。因此，恶臭假单胞菌F1去饱和缺陷并非由于恶臭假单胞菌F1的DesA蛋白有缺陷，而可能是由于电子传递过程中一个活性较弱的成分。
