Lipopolysaccharide translocation across the Gram-negative inner membrane; development and exploitation of reagents and knowledge to guide early stage

脂多糖(LPS)是革兰氏阴性杆菌高度保护性细胞表面的关键成分。脂多糖是通过一系列酶和称为LPT复合体的多蛋白质运输系统的作用而在细胞表面产生和显示的。如果脂多糖的产生受到限制，细菌的生存就会受到影响，而且基因研究表明，参与脂多糖产生/运输的许多编码蛋白质的基因是必不可少的。高水平的研究活动集中在细胞质生物合成酶和蛋白质的特性上，这些蛋白质涉及从周质到细胞表面的外膜转移。我们的计划是专注于缺失的区域，并描述那些参与成分跨内膜转移的蛋白质。需要研究的三个关键蛋白是MSBA、LptF和LptG。MSBA是一种ATPase驱动的翻转酶，它与潜在的异源二聚体LptF-LptG对结合作用。它是一种三磷酸腺苷结合盒运输器，折叠是已知的。然而，对于LptF-G，没有已知的同源结构。LptF和LptG蛋白通常有大约20%的序列同源性，二级结构预测表明存在一个共同的折叠，预计由6个跨膜螺旋组成。这两种蛋白质可能形成同源或异源二聚体，我们的目标是在项目开始时澄清这一特征。

Lipopolysaccharide (LPS) is a key component of the highly protective cell surface of Gram-negative pathogens. LPS is produced and displayed on the cell surface by the actions of a series of enzymes and a multi-protein transport system termed the Lpt complex. Bacterial survival is compromised if LPS production is curtailed and genetic studies reveal that many of the genes encoding proteins involved in LPS production/transport are essential. A high level of research activity has concentrated on characterisation of the cytosolic biosynthetic enzymes and the proteins that involve transfer from periplasm to cell surface, at the outer membrane. Our plan is to focus on the missing area, and to characterise those proteins involved in the transfer of components across the inner membrane. The three key proteins to be investigated are MsbA, LptF and LptG. MsbA is an ATPase driven flippase, which acts in conjunction with thepotentially heterodimeric LptF-LptG pair. It is an ATP-binding cassette transporter and the fold is known. However, for LptF-G there is are no known orthologous structures. The LptF and LptG proteins typically share about 20% sequence identity and secondary structure predictions suggest a common fold, predicted to comprise 6 transmembrane helices, is present. These two proteins may form homo or heterodimers, a feature we aim to clarify at the onset of the project.