Structural heterogeneity and environmentally regulated remodeling of Francisella tularensis subspecies novicida lipid a characterized by tandem mass spectrometry
Structural heterogeneity and environmentally regulated remodeling of Francisella tularensis subspecies novicida lipid a characterized by tandem mass spectrometry
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DOI：
10.1016/j.jasms.2007.03.008
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发表时间：
2007-06-01
影响因子：
3.2
通讯作者：
Ernst, Robert K.
中科院分区：
文献类型：
--
作者：
Shaffer, Scott A.;Harvey, Megan D.;Ernst, Robert K.
利用负电喷雾电离和线性离子阱傅里叶变换离子回旋共振（IT-FT-ICR）混合质谱仪对土拉弗朗西斯菌（Francisella tularensis）亚种novicida (Fn) U112衍生的环境调节脂质A进行了结构表征。结果表明，相对于37℃，在25℃和37℃的条件下，脂质a分子结构的合成具有独特的特征，分子种类被发现是四酰化的，共享一个保守的氨基葡萄糖双糖骨架，一个与氨基葡萄糖还原连接的半乳糖-1-磷酸，以及多个O和n连接的脂肪酰基。用MSn扫描技术在高质量和名义质量分辨率下对去质子化分子进行了研究，发现它们是复杂的非均质混合物，其结构根据O-和n -链脂肪酸基取代基的位置和身份而不同。对于由5个峰组成的优势离子系列，鉴定出30个独特的脂质A结构。每个结构的相对丰度估计来自MS2到MS4实验中可比解离途径的MS相对丰度比和片段离子比。结果表明，还原氨基葡萄糖的酰胺连接脂肪酸在25℃的生长条件下更倾向于3-羟基十六烷酸取代基，而在37℃的生长条件下更倾向于3-羟基十八烷酸取代基。
The structural characterization of environmentally-regulated lipid A derived from Francisella tularensis subspecies novicida (Fn) U112 is described using negative electrospray ionization with a linear ion trap Fourier transform ion cyclotron resonance (IT-FT-ICR) hybrid mass spectrometer. The results indicate that a unique profile of lipid A molecular structures are synthesized in response to Fn growth at 25 degrees C versus 37 degrees C. Molecular species were found to be tetra-acylated, sharing a conserved glucosamine disaccharide backbone, a galactosamine-1-phosphate linked to the reducing glucosamine, and multiple O- and N-linked fatty acyl groups. Deprotonated molecules were interrogated by MSn scanning techniques at both high and nominal mass resolution and were found to be complex heterogeneous mixtures where structures differed based on the positions and identities of the O- and N-linked fatty acyl substituents. For the dominant ion series, which consisted of five peaks, 30 unique lipid A structures were identified. Estimates for the relative abundance of each structure were derived from MS relative abundance ratios and fragment ion ratios from comparable dissociation pathways from MS2 through MS4 experiments. The results suggest a remodeling pathway in which the amide linked fatty acid of the reducing glucosamine favors a 3-hydroxyhexadecanoic acid substituent for growth conditions at 25 degrees C versus a 3-hydroxyoctadecanoic acid substituent for growth conditions at 37 degrees C.