Investigation of Novel Lipid A Structural Features

描述(由申请人提供)： 在革兰氏阴性细菌中，脂类A构成了独特的糖脂脂多糖(LPS)的疏水膜锚。它是生存所必需的，并通过激活TLR4受体作为一种强大的免疫刺激剂。多年来，人们对大肠杆菌类脂A的结构和生物合成途径进行了广泛的研究。它是一种氨基葡萄糖的六酰化二糖，在1-和4‘-位被磷酸盐取代。最近，问号钩端螺旋体的类脂A结构已被解决，并揭示了两个有趣的特征。1-磷酸甲基化，4‘-位去磷酸化。研究还发现，钩端螺旋体内毒素在先天免疫反应中激活TLR2，而不是TLR4。了解这些修饰的酶学特性不仅有助于理解脂质A的生物合成，而且还将为发病机制提供新的分子见解。具体地说，这项建议侧重于(L-11)1-甲基转移酶和PIE 4‘-磷酸酶的鉴定和特性；以及(Iii)研究这些结构修饰对独特的rTLR2依赖的免疫反应的影响。

DESCRIPTION (provided by applicant): In Gram-negative bacteria, lipid A constitutes the hydrophobic membrane anchor of the unique glycolipid lipopolysaccharide (LPS). It is essential for viability and serves as a potent immunostimulant by activating the TLR4 receptor. The structure and biosynthetic pathway of Escherichia coli lipid A has been extensively haracterized over the years. It is a hexaacylated disaccharide of glucosamine that is substituted at the 1- and 4'-positions with phosphate. Recently, the lipid A structure of the spirochete Leptospira interrogans has been solved, and two interesting features were revealed. The 1-phosphate is methylated, and the 4'-position is dephosphorylated. It has also been discovered that leptospiral LPS activates TLR2 in the innate immune response instead of TLR4. Understanding the enzymology of these modifications will not only facilitate the understanding of lipid A biosynthesis, but it will also provide new molecular insights into pathogenesis. Specifically, this proposal focuses on (l-ll) identification and characterization of the 1-methyltransferase and pie 4'-phosphatase; and (III) investigation of the effects these structural modifications have on the unique rTLR2-dependent immune response.