Biosynthesis of Undecaprenyl Phosphate-Galactosamine and Undecaprenyl Phosphate-Glucose in Francisella novicida
Biosynthesis of Undecaprenyl Phosphate-Galactosamine and Undecaprenyl Phosphate-Glucose in Francisella novicida
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DOI：
10.1021/bi802212t
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发表时间：
2009-02-17
期刊：
影响因子：
2.9
通讯作者：
Ractz, Christian R. H.
中科院分区：
文献类型：
--
作者：
Song, Feng;Guan, Ziqiang;Ractz, Christian R. H.
土拉弗朗西斯菌亚种的脂质 A。 novicida 含有与其 1-磷酸基团相连的半乳糖胺 (GalN) 残基。如前文所示，该 GalN 单元从前体十一碳烯基磷酸-β-D-GalN 转移到脂质 A。新杀弗朗西斯菌的一小部分游离脂质 A 在 6' 位置用葡萄糖残基进一步修饰。我们现在证明，大肠杆菌 ArnC 的两个 F. novicida 同源物（命名为 FlmF1 和 FlmF2）分别对于用葡萄糖和 GalN 修饰脂质 A 至关重要。在大肠杆菌中表达的重组FlmF1在体外选择性地缩合十一异戊二烯基磷酸酯和UDP-葡萄糖，形成十一异戊二烯基磷酸酯-葡萄糖。重组FlmF2选择性催化磷酸十一烯基酯和UDP-N-乙酰半乳糖胺缩合生成磷酸十一烯基酯-N-乙酰半乳糖胺。基于对 F. novicida 的 flmF1 和 flmF2 突变体的脂质 A 组成的分析，我们得出结论，FlmF1 生成用葡萄糖修饰 F. novicida 游离脂质 A 的供体底物，而 FlmF2 生成 GalN 供体底物的直接前体，磷酸十一异戊二烯基磷酸-β-D-GalN。一种新型脱乙酰酶，存在于 h. novicida，从磷酸十一异戊二烯基-N-乙酰半乳糖胺中除去乙酰基，生成磷酸十一异戊二烯基-β-D-GalN。这种脱乙酰酶可能与去甲酰基酶具有类似的功能，该酶在大肠杆菌和鼠伤寒沙门氏菌的多粘菌素抗性菌株中从磷酸十一异戊二烯基磷酸-4-脱氧-4-甲酰氨基-α-L-阿拉伯糖产生十一异戊二烯基磷酸-4-氨基-4-脱氧-α-L-阿拉伯糖。
Lipid A of Francisella tularensis subsp. novicida contains a galactosamine (GalN) residue linked to its 1-phosphate group. As shown in the preceding paper, this GalN unit is transferred to lipid A from the precursor undecaprenyl phosphatc-beta-D-GalN. A small portion of the free lipid A of Francisella novicida is further modified with a glucose residue at position-6'. We now demonstrate that the two F. novicida homologues of Escherichia coli ArnC, designated FlmF1 and FlmF2, are essential for lipid A modification with glucose and GalN, respectively. Recombinant FlmF1 expressed in E. coli selectively condenses undecaprenyl phosphate and UDP-glucose in vitro to form undecaprenyl phosphate-glucose. Recombinant FlmF2 selectively catalyzes the condensation of undecaprenyl phosphate and UDP-N-acetylgalactosamine to generate Undecaprenyl phosphate-N-acetylgalactosamine. On the basis of an analysis of the lipid A composition of flmF1 and flmF2 mutants of F. novicida, we conclude that FlmF1 generates the donor substrate for the modification of F. novicida free lipid A with glucose, whereas FlmF2 generates the immediate precursor of the GalN donor substrate, undecaprenyl phosphate-beta-D-GalN. A novel deacetylase, present in membranes of h. novicida, removes the acetyl group from undecaprenyl phosphate-N-acetyl galactosamine to yield undecaprenyl phosphate-beta-D-GalN. This deacetylase may have an analogous function to the deformylase that generates undecaprenyl phosphate-4-amino-4-deoxy-alpha-L-arabinose from undecaprenyl phosphate-4-deoxy-4-formylamino-alpha-L-arabinose in polymyxin-resistant strains of E. coli and Salmonella typhimurium.