Ornithine Transcarbamylase ArgK Plays a Dual role for the Self-defense of Phaseolotoxin Producing Pseudomonas syringae pv. phaseolicola.
Ornithine Transcarbamylase ArgK Plays a Dual role for the Self-defense of Phaseolotoxin Producing Pseudomonas syringae pv. phaseolicola.
复制标题
鸟氨酸转氨甲酰酶 ArgK 在产生菜豆毒素的丁香假单胞菌的自卫中发挥双重作用。
DOI：
10.1038/srep12892
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发表时间：
2015-08-10
影响因子：
4.6
通讯作者：
Zhao C
中科院分区：
文献类型：
--
作者：
Chen L;Li P;Deng Z;Zhao C
丁香假单胞菌是一种广泛传播于陆生植物上的植物致病菌。磺胺二氨基膦酰三肽相毒素（PHTs）。phaseolicola和p.s ynringae。猕猴桃属，是一类抗代谢植物毒素。pht抑制宿主细胞鸟氨酸转氨基甲酰基酶（OTCase）活性，诱导精氨酸营养不良表型。PHT的生物合成依赖于温度，在18°C左右进行光学合成，而在28°C以上受阻。抗PHT OTCase ArgK作为一种功能性替代品，替代了内源性OTCase ArgF，后者是PHT的作用靶点，赋予PHT生产商自我抗性。我们推测argK可能受到PHT生物合成前体的直接调控和温度以未知方式间接调控。在PHT生物合成基因簇中未检测到转录调节因子和热调节相关蛋白编码基因。该三肽Cit-Ala-hArg是PHT生物合成途径的副产物。以三肽Orn-Ala-hArg和氨甲酰磷酸为底物，由ArgK催化生成Cit-Ala-hArg。结果表明，ArgK不仅如之前报道的那样提供了替代的精氨酸来源，而且还通过将PHT生物合成前体转化为无毒的Cit-Ala-hArg储层来控制PHT的产量，为生产商提供了自我保护。
Pseudomonas syringae is a phytopathogenic bacterium widely spread on terrestrial plants. Sulfodiaminophosphinyl tripeptide Phaseolotoxins (PHTs), produced by P. syringae pv. phaseolicola and P. syringae pv. actinidiae, represent a kind of antimetabolic phytotoxins. PHTs inhibit host cell Ornithine transcarbamylase (OTCase) activity and induce Arginine auxotrophic phenotype. The biosynthesis of PHT is temperature dependent, being optically produced at around 18 °C, while blocked above 28 °C. PHT resistant OTCase ArgK acts as a functional replacement of housekeeping OTCase ArgF, which is the acting target of PHT, to confer PHT producers with self-resistance. It was postulated that argK might be regulated directly by a PHT biosynthetic precursor and indirectly by temperature with an unknown manner. Neither transcriptional regulator nor thermal regulation related protein encoding gene was detected from PHT biosynthetic gene cluster. The tripeptide, Cit-Ala-hArg, was identified to be a by-product of PHT biosynthetic pathway in this report. Formation of Cit-Ala-hArg was catalyzed by ArgK with tripeptide Orn-Ala-hArg and carbamyl phosphate as substrates. It showed that ArgK not only provided alternative Arginine source as reported previously, but also controlled the production of PHTs by converting PHT biosynthetic precursors to nontoxic Cit-Ala-hArg reservoir for producers’ self-defense.