Biological Nitrogen Fixation
Biological Nitrogen Fixation
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生物固氮
DOI：
10.1002/9781119053095.ch34
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发表时间：
2015
期刊：
影响因子：
--
通讯作者：
Prell J
中科院分区：
文献类型：
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作者：
Prell J
在根瘤菌Rlv3841菌株中PTSNtr系统的编码EINtr的ptsP突变引起了许多细菌观察到的多效性表型。该突变体形成干燥的菌落，在有机氮或二羧酸盐上生长不良。最引人注目的是，ptsP突变体具有广泛的ATP依赖性ABC转运蛋白的低活性。这种激活的缺乏，发生在术后，可以解释许多多效性效应。相反，质子偶联转运系统在aptsPmutant中未受到抑制。PtsP的调节还涉及两个拷贝的编码EIIANtr的ptsN，导致磷酸化级联反应。与大肠杆菌一样，Rlv3841 PTSNtr系统也通过转录激活高亲和力ATP依赖性K+转运蛋白KdpABC来调节K+稳态。这涉及双组分传感器调节剂对KdpDE与未磷酸化的EIIANtr的直接相互作用。重要的是，不能磷酸化PtsN1或PtsN2的ptsPmutants具有完全激活的KdpABC转运蛋白。这与ABC转运蛋白所观察到的模式相反，ABC转运蛋白显然需要PtsN的磷酸化。这些结果表明，ATP依赖性转运可能是通过PTSN响应细胞能量电荷来调节的。ABC运输可能在低能量电荷下失活，保存ATP用于基本过程，包括K+稳态。
Mutation ofptsPencoding EINtrof the PTSNtrsystem inRhizobium leguminosarumstrain Rlv3841 caused a pleiotropic phenotype as observed with many bacteria. The mutant formed dry colonies and grew poorly on organic nitrogen or dicarboxylates. Most strikingly theptsPmutant had low activity of a broad range of ATP‐dependent ABC transporters. This lack of activation, which occurred post‐translationally, may explain many of the pleiotropic effects. In contrast proton‐coupled transport systems were not inhibited in aptsPmutant. Regulation by PtsP also involves two copies ofptsNthat code for EIIANtr, resulting in a phosphorylation cascade. As inEscherichia coli, the Rlv3841 PTSNtrsystem also regulates K+homeostasis by transcriptional activation of the high‐affinity ATP‐dependent K+transporter KdpABC. This involves direct interaction of a two‐component sensor regulator pair KdpDE with unphosphorylated EIIANtr. Critically,ptsPmutants, which cannot phosphorylate PtsN1 or PtsN2, had a fully activated KdpABC transporter. This is the opposite pattern from that observed with ABC transporters which apparently require phosphorylation of PtsN. These results suggest that ATP‐dependent transport might be regulated via PTSNtrresponding to the cellular energy charge. ABC transport may be inactivated at low energy charge, conserving ATP for essential processes including K+homeostasis.