A novel outer membrane lipoprotein, LolB (HemM), involved in the LolA (p20)-dependent localization of lipoproteins to the outer membrane of Escherichia coli
A novel outer membrane lipoprotein, LolB (HemM), involved in the LolA (p20)-dependent localization of lipoproteins to the outer membrane of Escherichia coli
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DOI：
10.1093/emboj/16.23.6947
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发表时间：
1997-12-01
期刊：
影响因子：
11.4
通讯作者：
Tokuda, H
中科院分区：
文献类型：
--
作者：
Matsuyama, S;Yokota, N;Tokuda, H
大肠杆菌的主要外膜脂蛋白(LPP)作为载体蛋白loA(P20)的复合体从内膜释放到周质中，然后被特异性地掺入外膜，鉴定了一个在LPP掺入过程中起关键作用的外膜蛋白，该蛋白的部分氨基酸序列与hemm的部分氨基酸序列相同，后者被认为在胞浆中合成5-氨基乙酰丙酸。与此相反，hemm的氨基酸序列推测该基因编码一种新的外膜脂蛋白，实际上，一种针对高纯度LOLB的抗体揭示了其外膜定位，并抑制了体外LPP在外膜上的掺入，此外，LOLB被合成为具有信号序列的前体，然后被加工成脂质修饰的成熟形式，一株在lac启动子-操纵子控制下具有染色体hemm的大肠杆菌菌株需要IPTG生长，这表明hemm(LOLB)是一个必需基因，由LOLB耗竭的细胞制备的外膜不含有LPP，当LPP-LOLA复合体与水溶性LOLB衍生物孵育时，LPP从LOLA转移到LOLB。从LOLA和LOLB的功能出发，讨论了大肠杆菌脂蛋白的外膜定位途径。
The Escherichia coli major outer membrane lipoprotein (Lpp) is released from the inner membrane into the periplasm as a complex with a carrier protein, LolA (p20), and is then specifically incorporated into the outer membrane, An outer membrane protein playing a critical role in Lpp incorporation was identified, and partial amino acid sequences of the protein, named LolB, were identical to those of HemM, which has been suggested to play a role in 5-aminolevulinic acid synthesis in the cytosol, In contrast to this suggested role, the deduced amino acid sequence of HemM implied that the gene encodes a novel outer membrane lipoprotein, Indeed, an antibody raised against highly purified LolB revealed its outer membrane localization, and inhibited irt vitro Lpp incorporation into the outer membrane, Furthermore, LolB was found to be synthesized as a precursor with a signal sequence and then processed to a lipid-modified mature form, An E. coli strain possessing chromosomal hemM under the control of the lac promoter-operator required IPTG for growth, indicating that hemM (lolB) is an essential gene, Outer membrane prepared from LolB-depleted cells did not incorporate Lpp, When the Lpp-LolA complex was incubated with a water-soluble LolB derivative, Lpp was transferred from LolA to LolB, Based on these results, the outer membrane localization pathway for E. coli lipoprotein is discussed with respect to the functions of LolA and LolB.