Elucidation of the 3-O-Deacylase Gene, pagL, Required for the Removal of Primary β-Hydroxy Fatty Acid from the Lipid A in the Nitrogen-fixing Endosymbiont Rhizobium etli CE3
Elucidation of the 3-O-Deacylase Gene, pagL, Required for the Removal of Primary β-Hydroxy Fatty Acid from the Lipid A in the Nitrogen-fixing Endosymbiont Rhizobium etli CE3
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DOI：
10.1074/jbc.m113.470484
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发表时间：
2013-04-26
影响因子：
4.8
通讯作者：
Carlson, Russell W.
中科院分区：
文献类型：
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作者：
Brown, Dusty B.;Muszynski, Artur;Carlson, Russell W.
到目前为止，固氮内共生体中负责脂质A 3-O-脱酰化的基因尚未被鉴定。几种革兰氏阴性动物病原体，如沙门氏菌、铜绿假单胞菌和支气管败血波氏杆菌含有外膜3-O-脱酰基酶（PagL），其与宿主免疫逃避有关。3-O-脱酰脂质A在固氮内共生菌、植物内生菌和植物病原体中的作用尚未研究。然而，D 'Haeze等人（D' Haeze，W.，Leoff，C.，Freshour，G.，诺埃尔，K. D、和Carlson，R. W.（2007）J.Biol.Chem.282，17101-17113）报道了来自分离自宿主豆根瘤的Rhizobium etli CE 3拟杆菌的脂多糖仅含有缺乏脂质A β-羟基肉豆蔻基残基的四酰化脂质A，这一观察结果与PagL活性在共生中重要的可能性一致。在R. etli基因组序列。利用这些信息，我们创建了来自R.等CE 3.使用质谱，我们证明了突变体缺乏3-O-脱酰脂质A。通过凝胶电泳和使用气相色谱/质谱的糖基组成分析确定，亲本和突变体LPS非常相似。然而，脂肪酸分析表明，突变体脂质A比亲本含有更大量的β-羟基十五烷酸。此外，该突变体在与寄主菜豆建立共生关系方面受到不利影响。
Until now, the gene responsible for the 3-O-deacylation of lipid A among nitrogen-fixing endosymbionts has not been characterized. Several Gram-negative animal pathogens such as Salmonella enterica, Pseudomonas aeruginosa, and Bordetella bronchiseptica contain an outer membrane 3-O-deacylase (PagL) that has been implicated in host immune evasion. The role of 3-O-deacylated lipid A among nitrogen-fixing endosymbionts, plant endophytes, and plant pathogens has not been studied. However, D'Haeze et al. (D'Haeze, W., Leoff, C., Freshour, G., Noel, K. D., and Carlson, R. W. (2007) J. Biol. Chem. 282, 17101-17113) reported that the lipopolysaccharide from Rhizobium etli CE3 bacteroids isolated from host bean root nodules contained exclusively tetraacylated lipid A that lacked a lipid A beta-hydroxymyristyl residue, an observation that is consistent with the possibility of PagL activity being important in symbiosis. A putative pagL gene was identified in the R. etli genome sequence. With this information, we created a pagL(-) mutant strain derived from R. etli CE3. Using mass spectrometry, we demonstrated that the mutant lacks 3-O-deacylated lipid A. The parent and mutant LPS were very similar as determined by gel electrophoresis and glycosyl composition analysis using gas chromatography/mass spectrometry. However, fatty acid analysis showed that the mutant lipid A contained larger amounts of beta-hydroxypentadecanoic acid than that of the parent. Furthermore, the mutant was adversely affected in establishing symbiosis with its host, Phaseolus vulgaris.