Department of Biochemistry and Molecular Biology, The Pennsylvania State University, University Park, Pennsylvania, USA.
Department of Biochemistry and Molecular Biology, The Pennsylvania State University, University Park, Pennsylvania, USA
J Bacteriol. 2018 May 24;200(12). doi: 10.1128/JB.00017-18. Print 2018 Jun 15.
Lipoteichoic acid (LTA) in is a poly-glycerophosphate polymer anchored to the outer surface of the cell membrane. LTA has numerous roles in cell envelope physiology, including regulating cell autolysis, coordinating cell division, and adapting to environmental growth conditions. LTA is often further modified with substituents, including d-alanine and glycosyl groups, to alter cellular function. While the genetic determinants of d-alanylation have been largely defined, the route of LTA glycosylation and its role in cell envelope physiology have remained unknown, in part due to the low levels of basal LTA glycosylation in We demonstrate here that utilizes a membrane-associated three-component glycosylation system composed of an undecaprenol (Und) -acetylglucosamine (GlcNAc) charging enzyme (CsbB; SAOUHSC_00713), a putative flippase to transport loaded substrate to the outside surface of the cell (GtcA; SAOUHSC_02722), and finally an LTA-specific glycosyltransferase that adds α-GlcNAc moieties to LTA (YfhO; SAOUHSC_01213). We demonstrate that this system is specific for LTA with no cross recognition of the structurally similar polyribitol phosphate containing wall teichoic acids. We show that while wild-type LTA has only a trace of GlcNAcylated LTA under normal growth conditions, amounts are raised upon either overexpressing CsbB, reducing endogenous d-alanylation activity, expressing the cell envelope stress responsive alternative sigma factor SigB, or by exposure to environmental stress-inducing culture conditions, including growth media containing high levels of sodium chloride. The role of glycosylation in the structure and function of lipoteichoic acid (LTA) is largely unknown. By defining key components of the LTA three-component glycosylation pathway and uncovering stress-induced regulation by the alternative sigma factor SigB, the role of -acetylglucosamine tailoring during adaptation to environmental stresses can now be elucidated. As the and glycosylation pathways compete for the same sites on LTA and induction of glycosylation results in decreased d-alanylation, the interplay between the two modification systems holds implications for resistance to antibiotics and antimicrobial peptides.
在 中，脂磷壁酸（LTA）是一种 anchored 到细胞膜外表面的多聚甘油磷酸聚合物。LTA 在细胞包膜生理学中具有多种作用，包括调节细胞自溶、协调细胞分裂和适应环境生长条件。LTA 通常进一步用取代基修饰，包括 D-丙氨酸和糖基基团，以改变细胞功能。虽然 D-丙氨酸化的遗传决定因素已基本确定，但 LTA 糖基化的途径及其在细胞包膜生理学中的作用仍不清楚，部分原因是 中基础 LTA 糖基化水平较低。我们在这里证明， 利用一种由十一烯醇（Und）-乙酰葡萄糖胺（GlcNAc）加载酶（CsbB；SAOUHSC_00713）、一种假定的翻转酶将负载的底物运输到细胞外表面（GtcA；SAOUHSC_02722）和最后一种将α-GlcNAc 部分添加到 LTA 的 LTA 特异性糖基转移酶组成的膜相关三组分糖基化系统。我们证明该系统特异性识别 LTA，与结构相似的多核糖醇磷酸含量壁磷壁酸没有交叉识别。我们表明，虽然在正常生长条件下，野生型 LTA 中只有痕量的 GlcNAc 化 LTA，但在过表达 CsbB、降低内源性 D-丙氨酸化活性、表达细胞包膜应激响应替代 sigma 因子 SigB 或暴露于环境应激诱导的培养条件下，包括含有高浓度氯化钠的生长培养基时，数量会增加。糖基化在 脂磷壁酸（LTA）结构和功能中的作用在很大程度上是未知的。通过定义 LTA 三组分糖基化途径的关键组成部分，并揭示替代 sigma 因子 SigB 诱导的应激调节作用，现在可以阐明在适应环境应激时 -乙酰葡萄糖胺修饰的作用。由于 和糖基化途径竞争 LTA 上的相同位点，并且糖基化的诱导导致 D-丙氨酸化减少，因此两种修饰系统之间的相互作用对抗生素和抗菌肽的耐药性具有影响。
