An outer membrane enzyme that generates the 2-amino-2-deoxy-gluconate moiety of Rhizobium leguminosarum lipid A.
An outer membrane enzyme that generates the 2-amino-2-deoxy-gluconate moiety of Rhizobium leguminosarum lipid A.
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一种外膜酶，可生成豆科根瘤菌脂质 A 的 2-氨基-2-脱氧-葡萄糖酸部分。
DOI：
10.1074/jbc.m300378200
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发表时间：
2003
期刊：
影响因子：
--
通讯作者：
Raetz,ChristianRH
中科院分区：
文献类型：
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作者：
Que-Gewirth,NanetteLS;Lin,Shanhua;Cotter,RobertJ;Raetz,ChristianRH
豆科根瘤菌和类脂质根瘤菌的结构与其它革兰氏阴性菌不同。而更典型的大肠杆菌脂A是葡糖胺的六酰化二糖，其在1和4′位被磷酸化，R.埃特利安德河豆科植物脂质A由缺乏磷酸盐的结构上相关的物质（指定为A-E）的混合物组成。所有5种组分中均存在一个保守的远端单元，由4′位具有半乳糖醛酸残基的二酰化葡糖胺部分和作为2′酰氧基酰基部分一部分的仲27-羟基二十八烷酰基（27-OH-C28）组成。近端是异质的，在酰基链的数量和长度以及糖本身的特性方面不同。在B和C中存在一个近端葡糖胺单元，但在D-1和E中发现一个不寻常的2-氨基-2-脱氧-葡糖酸部分。我们现在证明，膜的R。豆科植物在需要添加去污剂并被EDTA抑制的反应中，Etlican可将B转化为D-1。苜蓿中华根瘤菌和E.我把这个活动。质谱分析表明，B在体外被氧化成一种比D-1大16个原子质量单位的物质。脂质A近端单位的氧化也证明了通过基质辅助激光解吸电离飞行时间质谱法在正和负模式下使用模型底物，1-脱磷酸脂质IVA。使用该材料，检测到额外的中间体（或副产物），初步鉴定为1-脱磷酸脂质IVA的内酯衍生物。这种酶被认为是一种氧化酶，只位于R的外膜上。通过蔗糖梯度分析判断为豆科植物瘤。据我们所知，氧化酶与革兰氏阴性菌的外膜还没有以前的报道。
The structures ofRhizobium leguminosarumandRhizobium etlilipid A are distinct from those found in other Gram-negative bacteria. Whereas the more typicalEscherichia colilipid A is a hexa-acylated disaccharide of glucosamine that is phosphorylated at positions 1 and 4′,R. etliandR. leguminosarumlipid A consists of a mixture of structurally related species (designated A–E) that lack phosphate. A conserved distal unit, comprised of a diacylated glucosamine moiety with galacturonic acid residue at position 4′ and a secondary 27-hydroxyoctacosanoyl (27-OH-C28) as part of a 2′ acyloxyacyl moiety, is present in all five components. The proximal end is heterogeneous, differing in the number and lengths of acyl chains and in the identity of the sugar itself. A proximal glucosamine unit is present in B and C, but an unusual 2-amino-2-deoxy-gluconate moiety is found in D-1 and E. We now demonstrate that membranes ofR. leguminosarumandR. etlican convert B to D-1 in a reaction that requires added detergent and is inhibited by EDTA. Membranes ofSinorhizobium melilotiandE. colilack this activity. Mass spectrometry demonstrates that B is oxidizedin vitroto a substance that is 16 atomic mass units larger, consistent with the formation of D-1. The oxidation of the lipid A proximal unit is also demonstrated by matrix-assisted laser desorption ionization time-of-flight mass spectrometry in the positive and negative modes using the model substrate, 1-dephospho-lipid IVA. With this material, an additional intermediate (or by product) is detected that is tentatively identified as a lactone derivative of 1-dephospho-lipid IVA. The enzyme, presumed to be an oxidase, is located exclusively in the outer membrane ofR. leguminosarumas judged by sucrose gradient analysis. To our knowledge, an oxidase associated with the outer membranes of Gram-negative bacteria has not been reported previously.