Characterization of a lipoprotein, NilC, required by Xenorhabdus nematophila for mutualism with its nematode host
Characterization of a lipoprotein, NilC, required by Xenorhabdus nematophila for mutualism with its nematode host
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DOI：
10.1111/j.1365-2958.2004.04271.x
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发表时间：
2004-10-01
影响因子：
3.6
通讯作者：
Goodrich-Blair, H
中科院分区：
文献类型：
--
作者：
Cowles, CE;Goodrich-Blair, H
嗜线虫杆菌是一种致病线虫--肉质斯氏线虫的伽马蛋白细菌互助体。嗜线虫需要NILC基因来定植其线虫宿主，NILC基因被预测为编码一种功能未知的外膜脂蛋白。这里描述的NILC的特征表明它是一个28 kDa的脂蛋白，通过N-末端信号序列直接进入周质。NILC的脂化和加工是通过在蛋白质细菌中保守的机制发生的。这项工作还表明，NILC是膜结合的，并定位于嗜线虫的周质，在大肠杆菌中表达时以外膜结合蛋白的形式产生。表达分析表明，NILC转录直接或间接受到LRP的抑制，这种调控联系可能解释了先前发现的Lrp：：Tn5突变体的线虫互惠缺陷。Lrp：：Tn5突变体产生一个额外的NILC转录本，这在体外生长的野生型细胞中没有观察到，并且在稳定期后期产生的NILC大约是野生型细胞的75倍。这些NILC表达、NILC定位和加工事件的基本特征为理解这种定植因子在嗜线虫/肉质链霉菌-宿主相互作用中的作用提供了坚实的基础。
Xenorhabdus nematophila is a gamma-proteobacterial mutualist of an insect-pathogenic nematode, Steinernema carpocapsae. X. nematophila requires nilC, a gene predicted to encode an outer membrane lipoprotein of unknown function, for colonization of its nematode host. Characterization of NilC, described here, demonstrated it is a 28 kDa lipoprotein directed to the periplasm by an N-terminal signal sequence. Lipidation and processing of NilC occurs by a mechanism that is conserved in proteobacteria. This work also showed NilC is membrane associated and oriented towards the periplasm of X. nematophila and is produced as an outer membrane-associated protein when expressed in Escherichia coli. Expression analyses revealed that nilC transcription is directly or indirectly repressed by Lrp, and this regulatory link may explain the nematode mutualism defect of a previously identified lrp::Tn5 mutant. An lrp::Tn5 mutant produces an additional nilC transcript, not observed in wild-type cells growing in vitro, and produces approximate to 75-fold more nilC than wild-type cells in late stationary phase. These fundamental characterizations of nilC expression and nilC localization and processing events have provided firm bases for understanding the role of this colonization factor in the X. nematophila/S. carpocapsae microbe-host interaction.