Structure of lipid A component of Rhizobium leguminosarum bv. phaseoli lipopolysaccharide. Unique nonphosphorylated lipid A containing 2-amino-2-deoxygluconate, galacturonate, and glucosamine.
Structure of lipid A component of Rhizobium leguminosarum bv. phaseoli lipopolysaccharide. Unique nonphosphorylated lipid A containing 2-amino-2-deoxygluconate, galacturonate, and glucosamine.
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发表时间：
1994-05
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通讯作者：
U. R. Bhat;L. S. Forsberg;R. W. Carlson
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作者：
U. R. Bhat;L. S. Forsberg;R. W. Carlson
豆根瘤菌脂多糖脂A类化合物的结构用烷基化分析、核磁共振波谱、电喷雾和快原子轰击质谱仪对菜豆(野生型菌株CE3)的脱氧酰化脂质A进行了研究。脂肪A的碳水化合物主链是由半乳糖醛酸、氨基葡萄糖和唯一糖2-氨基-2-脱氧葡萄糖酸组成的三糖，在脂多糖中未见报道。核磁共振和乙基化分析表明，半乳糖醛酸以α-1，4-键连接到氨基葡萄糖上，而氨基醛酸残基可能以1，5-内酯的形式存在，以苷元的形式连接到氨基葡萄糖上，从而占据了分子的还原端。所得主链是亲水性的，类似于通常从肠道细菌脂多糖中观察到的双磷酸化氨基葡萄糖二糖，因为非还原末端和还原末端都带有带负电荷的取代基。豆类根瘤菌脂A的脂肪酸以O-和N-酰基取代的形式与氨基葡萄糖和2-氨基葡萄糖酸结合。所有脂肪酸都是由3-羟基肉豆蔻酸酯(3-OH-C14.0)、3-羟基十五酸(3-OH-C15.0)、3-羟基棕榈酸酯(3-OH-C16.0)、3-羟基硬脂酸酯(3-OH-C18.0)和27-羟基二十八烷酸(27-OH-C28.0)组成的羟基化脂肪酸，摩尔比约为3：0.2：1：0.6：1。然而，长链27-羟基脂肪酸在27-羟基位置携带酯连接的β-羟基丁酸酯。脱氧-酰化脂质A的快速原子轰击质谱学表明，由于两个酰胺键上的脂肪酸不均匀，存在两个分子物种，相差28个质量单位。一种是酰胺连接的3-OH-C14.0和3-OH-C16.0，另一种是3-OH-C14.0和3-OH-C18.0。每个分子物种也以醛内酯的形式存在，在((M+H)+)-18处产生分子离子。酰胺类脂肪酸的异质性进一步区分了根瘤菌类脂A和肠源性类脂AS。
The structure of lipid A from the lipopolysaccharide of Rhizobium leguminosarum bv. phaseoli (wild type strain CE3) was investigated by alkylation analysis, nuclear magnetic resonance spectroscopy, and electrospray and fast atom bombardment mass spectrometry of the de-O-acylated lipid A. The lipid A carbohydrate backbone was shown to be a trisaccharide containing galacturonic acid, glucosamine, and the unique sugar 2-amino-2-deoxygluconic acid, previously unreported in lipopolysaccharides. Nuclear magnetic resonance spectroscopy and ethylation analyses revealed that the galacturonic acid is alpha-1,4-linked to the glucosamine, while the amino aldonic acid residue, which may exist as the 1,5-lactone, is attached as an aglycone to the glucosamine and, thus, occupies the reducing end of the molecule. The resulting backbone is hydrophilic and analogous to the commonly observed bisphosphorylated glucosamine disaccharide from enteric bacterial lipopolysaccharides in that both the nonreducing and reducing ends carry negatively charged substituents. The fatty acids of the R. leguminosarum lipid A are attached both as O- and N-acyl substituents to glucosamine and 2-aminogluconate. All fatty acids are hydroxylated consisting of 3-hydroxymyristate (3-OH-C14.0), 3-hydroxypentadecanoate (3-OH-C15.0), 3-hydroxypalmitate (3-OH-C16.0), 3-hydroxystearate (3-OH-C18.0), and 27-hydroxyoctacosanoate (27-OH-C28.0) in the approximate mole ratio 3:0.2:1:0.6:1. Unlike lipid As from enteric bacteria, the R. leguminosarum lipid A lacks 3-acyloxyacyl substituents; however, the long chain 27-hydroxy fatty acid carries ester-linked beta-hydroxybutyrate at the 27-hydroxy position. Fast atom bombardment mass spectrometry of the de-O-acylated lipid A demonstrated the presence of 2 molecular species that differ by 28 mass units due to fatty acid heterogeneity at the two amide linkages. One species carries amide-linked 3-OH-C14.0 and 3-OH-C16.0; the second species carries 3-OH-C14.0 and 3-OH-C18.0. Each molecular species also exists as the aldonolactone, yielding molecular ions at ((M+H)+)-18. The heterogeneity in the amide-linked fatty acids further distinguishes the Rhizobium lipid A from enteric lipid As.