A specificity determinant for phosphorylation in a response regulator prevents in vivo cross-talk and modification by acetyl phosphate
A specificity determinant for phosphorylation in a response regulator prevents in vivo cross-talk and modification by acetyl phosphate
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DOI：
10.1073/pnas.1113013108
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发表时间：
2011-12-13
影响因子：
11.1
通讯作者：
Hendrixson, David R.
中科院分区：
文献类型：
--
作者：
Boll, Joseph M.;Hendrixson, David R.
细菌双组分系统（TCSs）通过同源组氨酸激酶（HKs）和反应调节因子（RRs）之间的磷酸化传递，感知刺激并在细胞内传递信号，从而改变基因表达或行为反应。同源HKs和RRs之间没有高的磷酸化特异性，不同tcs之间可能发生交叉磷酸化或交叉对话，并减少对适当刺激的反应。减少串扰的一些机制涉及hk控制同源RR磷酸化水平。可以想象，一些RRs可能已经进化出了与hk无关的策略，以使自己免受与乙酰磷酸（AcP）或其他小磷供体代谢物的串扰。空肠弯曲杆菌鞭毛生物合成的最初步骤刺激从FlgS HK到FlgR RR的磷转移，以促进sigma（54）依赖性鞭毛基因的表达。我们发现FlgR c端结构域（CTD）在NtrC RR家族中通常作为dna结合结构域发挥作用，是限制AcP体内串扰的特异性决定因素。缺乏CTD的FlgR（FlgR(Delta CTD)）使用FlgS或AcP作为体内磷供体，可以在Delta FlgS突变体中重新编程，通过AcP水平响应细胞营养状况。尽管acp介导的FlgR（δ CTD）激活促进了WT鞭毛基因的表达，但鞭毛的生物合成受到了损害。我们认为FlgR CTD阻止AcP的磷转移，因此FlgR仅对FlgS作出反应，以促进鞭毛基因的适当表达和鞭毛。除了限制非同源HKs和RRs之间串扰的机制外，我们的研究表明，RRs可以拥有阻止RRs与内源性代谢物AcP之间体内串扰的结构域，以确保信号的特异性。
Bacterial two-component systems (TCSs) sense stimuli and transduce signals intracellularly through phosphotransfer between cognate histidine kinases (HKs) and response regulators (RRs) to alter gene expression or behavioral responses. Without high phosphotransfer specificity between cognate HKs and RRs, cross-phosphorylation or cross-talk between different TCSs may occur and diminish responses to appropriate stimuli. Some mechanisms to reduce cross-talk involve HKs controlling levels of cognate RR phosphorylation. Conceivably, some RRs may have evolved HK-independent strategies to insulate themselves from cross-talk with acetyl phosphate (AcP) or other small phosphodonor metabolites. Initial steps in flagellar biosynthesis in Campylobacter jejuni stimulate phosphotransfer from the FlgS HK to the FlgR RR to promote sigma(54)-dependent flagellar gene expression. We discovered that the FlgR C-terminal domain (CTD), which commonly functions as a DNA-binding domain in the NtrC RR family, is a specificity determinant to limit in vivo cross-talk from AcP. FlgR lacking the CTD (FlgR(Delta CTD)) used FlgS or AcP as an in vivo phosphodonor and could be reprogrammed in Delta flgS mutants to respond to cellular nutritional status via AcP levels. Even though exclusive AcP-mediated activation of FlgR(Delta CTD) promoted WT flagellar gene expression, proper flagellar biosynthesis was impaired. We propose that the FlgR CTD prevents phosphotransfer from AcP so that FlgR is solely responsive to FlgS to promote proper flagellar gene expression and flagellation. In addition to mechanisms limiting cross-talk between noncognate HKs and RRs, our work suggests that RRs can possess domains that prevent in vivo cross-talk between RRs and the endogenous metabolite AcP to ensure signaling specificity.