IN-VITRO SULFOTRANSFERASE ACTIVITY OF RHIZOBIUM-MELILOTI NODH PROTEIN - LIPOCHITOOLIGOSACCHARIDE NODULATION SIGNALS ARE SULFATED AFTER SYNTHESIS OF THE CORE STRUCTURE
IN-VITRO SULFOTRANSFERASE ACTIVITY OF RHIZOBIUM-MELILOTI NODH PROTEIN - LIPOCHITOOLIGOSACCHARIDE NODULATION SIGNALS ARE SULFATED AFTER SYNTHESIS OF THE CORE STRUCTURE
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DOI：
10.1073/pnas.92.7.2706
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发表时间：
1995-03-28
影响因子：
11.1
通讯作者：
KONDOROSI, A
中科院分区：
文献类型：
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作者：
SCHULTZE, M;STAEHELIN, C;KONDOROSI, A
根瘤菌共同的结节基因产物NodABC参与核心脂壳低聚糖（Nod因子）结构的合成，而宿主特异性结节基因的产物对于不同的结构修饰是必需的，而不同的根瘤菌物种的结构修饰有所不同。与苜蓿根瘤菌 Nod 信号相连的硫酸基团对于宿主植物苜蓿的活性是必需的，而它的缺失则使得 Nod 因子对非宿主植物野豌豆具有活性。因此，该取代基是宿主特异性的主要决定因素。 Nod因子的确切生物合成途径尚未完全阐明。特别是，目前尚不清楚为什么某些化学修饰以高保真度引入，而另一些则不准确，从而产生由单一根瘤菌菌株产生的一系列不同的Nod因子结构。使用从表达苜蓿根瘤菌 nodH 基因的大肠杆菌中获得的蛋白质提取物和部分纯化的重组 NodH 蛋白，我们在此证明了 NodH 依赖性体外磺基转移酶活性。 Nod 因子、壳寡糖及其脱乙酰衍生物的动力学分析表明，Nod 因子是硫酸盐转移的首选底物。此外，四聚体Nod因子NodRm-IV是比三聚体NodRm-III或五聚体NodRm-V更好的底物。这些数据表明，核心脂壳寡糖结构必须在用硫酸基团进行宿主特异性修饰之前合成。由于苜蓿四聚体Nod因子是最丰富和最活跃的，因此NodH对适当四聚体底物的高亲和力保证了其修饰，从而有助于宿主特异性行为的保真度。
The Rhizobium common nod gene products NodABC are involved in the synthesis of the core lipochitooligosaccharide (Nod factor) structure, whereas the products of the host-specific nod genes are necessary for diverse structural modifications, which vary in different Rhizobium species. The sulfate group attached to the Rhizobium meliloti Nod signal is necessary for activity on the host plant alfalfa, while its absence renders the Nod factor active on the non-host plant vetch. This substituent is therefore a major determinant of host specificity. The exact biosynthetic pathway of Nod factors has not been fully elucidated. In particular, it is not known why some chemical modifications are introduced with high fidelity whereas others are inaccurate, giving rise to a family of different Nod factor structures produced by a single Rhizobium strain. Using protein extracts and partially purified recombinant NodH protein obtained from Escherichia coli expressing the R. meliloti nodH gene, we demonstrate here NodH-dependent in vitro sulfotransferase activity. Kinetic analyses with Nod factors, chitooligosaccharides, and their deacetylated derivatives revealed that Nod factors are the preferred substrate for the sulfate transfer. Moreover, the tetrameric Nod factor, NodRm-IV, was a better substrate than the trimer, NodRm-III, or the pentamer, NodRm-V. These data suggest that the core lipochitooligosaccharide structure must be sythesized prior to its host-specific modification with a sulfate group. Since in R. meliloti tetrameric Nod factors are the most abundant and the most active ones, high affinity of NodH for the appropriate tetrameric substrate guarantees its modification and thus contributes to the fidelity of host-specific behavior.