Institute for Integrative Biology of the Cell (I2BC), CEA, CNRS, Univ. Paris-Sud, Université Paris-Saclay, 91198, Gif-sur-Yvette cedex, France.
Present address: Laboratoire de Biologie Physico-Chimique des Protéines Membranaires, CNRS, Institut de Biologie Physico-Chimique, F-75005 Paris, France.
Microbiology (Reading). 2020 Aug;166(8):759-776. doi: 10.1099/mic.0.000937. Epub 2020 Jun 3.
Bacterial lipoproteins are secreted proteins that are post-translationally lipidated. Following synthesis, preprolipoproteins are transported through the cytoplasmic membrane via the Sec or Tat translocon. As they exit the transport machinery, they are recognized by a phosphatidylglycerol::prolipoprotein diacylglyceryl transferase (Lgt), which converts them to prolipoproteins by adding a diacylglyceryl group to the sulfhydryl side chain of the invariant Cys residue. Lipoprotein signal peptidase (LspA or signal peptidase II) subsequently cleaves the signal peptide, liberating the α-amino group of Cys, which can eventually be further modified. Here, we identified the and genes from and found that they are unique but not essential. We found that Lgt is necessary for the acylation and membrane anchoring of two model lipoproteins expressed in this species: MusE, a maltose-binding lipoprotein, and LppX, a lipoprotein. However, Lgt is not required for these proteins' signal peptide cleavage, or for LppX glycosylation. Taken together, these data show that in the association of some lipoproteins with membranes through the covalent attachment of a lipid moiety is not essential for further post-translational modification.
细菌脂蛋白是经翻译后脂质化的分泌蛋白。在前原蛋白合成后，通过 Sec 或 Tat 转位蛋白穿过细胞质膜运输。当它们离开运输机制时，它们被磷脂酰甘油：前原蛋白二酰甘油转移酶（Lgt）识别，该酶通过在不变半胱氨酸残基的巯基侧链上加二酰甘油基团将它们转化为前原蛋白。脂蛋白信号肽酶（LspA 或信号肽 II）随后切割信号肽，释放 Cys 的α-氨基，最终可以进一步修饰。在这里，我们从 中鉴定出 和 基因，发现它们是独特的，但不是必需的。我们发现 Lgt 对于两种在该物种中表达的模型脂蛋白的酰化和膜锚定是必需的：MusE，一种麦芽糖结合脂蛋白，和 LppX，一种 脂蛋白。然而，Lgt 对于这些蛋白质的信号肽切割或 LppX 糖基化不是必需的。总之，这些数据表明，在 中，一些脂蛋白通过共价连接脂质部分与膜的结合对于进一步的翻译后修饰不是必需的。
