通过PstSCAB磷酸转运蛋白的替代构象进行磷酸信号传递。,BMC Microbiology

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通过PstSCAB磷酸转运蛋白的替代构象进行磷酸信号传递。
BMC Microbiology ( IF 4.0 ) Pub Date : 2018-01-21 , DOI: 10.1186/s12866-017-1126-z
Ramesh K Vuppada ₁ , Colby R Hansen ₁ , Kirsta A P Strickland ₁ , Keilen M Kelly ₁ , William R McCleary ₁

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背景技术磷酸盐是生命必不可少的化合物。大肠杆菌采用信号转导途径来控制高亲和力获取磷酸盐和利用其他磷源所需基因的表达。仅当环境磷酸盐有限时才表达这些基因。该信号通路的七个基因编码两组分调节蛋白PhoB和PhoR，以及高亲和力磷酸盐转运蛋白PstSCAB和辅助蛋白PhoU。由于传感器激酶PhoR没有周质感觉域，因此这些细胞感知环境磷酸盐的机制尚不清楚。本文探讨了以下假设：PstSCAB转运蛋白的交替构象是正常磷酸盐转运周期的一部分，表明磷酸酯充足或磷酸盐限制。结果我们测试了PstB的两个变异体，预测它们的信号输出可将蛋白质锁定在两种构象中的一种。我们观察到，pstBQ160K突变体预计位于向内的，开放的构象，表明磷酸充足，而pstBE179Q突变体预计驻留在向内的，封闭的构象，表明磷酸饥饿。两个突变体均未显示磷酸盐转运。结论这些结果支持以下假设：PhoR和PhoU可以检测到PstSCAB转运蛋白的交替构象。

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Phosphate signaling through alternate conformations of the PstSCAB phosphate transporter.

BACKGROUND Phosphate is an essential compound for life. Escherichia coli employs a signal transduction pathway that controls the expression of genes that are required for the high-affinity acquisition of phosphate and the utilization of alternate sources of phosphorous. These genes are only expressed when environmental phosphate is limiting. The seven genes for this signaling pathway encode the two-component regulatory proteins PhoB and PhoR, as well as the high-affinity phosphate transporter PstSCAB and an auxiliary protein called PhoU. As the sensor kinase PhoR has no periplasmic sensory domain, the mechanism by which these cells sense environmental phosphate is not known. This paper explores the hypothesis that it is the alternating conformations of the PstSCAB transporter which are formed as part of the normal phosphate transport cycle that signal phosphate sufficiency or phosphate limitation. RESULTS We tested two variants of PstB that are predicted to lock the protein in either of two conformations for their signaling output. We observed that the pstBQ160K mutant, predicted to reside in an inward-facing, open conformation signaled phosphate sufficiency whereas the pstBE179Q mutant, predicted to reside in an outward-facing, closed conformation signaled phosphate starvation. Neither mutant showed phosphate transport. CONCLUSIONS These results support the hypothesis that the alternating conformations of the PstSCAB transporter are sensed by PhoR and PhoU. This sensory mechanism thus controls the alternate autokinase and phospho-PhoB phosphatase activities of PhoR, which ultimately control the signaling state of the response regulator PhoB.

更新日期：2018-01-19

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