Structure and mechanism of a Hypr GGDEF enzyme that activates cGAMP signaling to control extracellular metal respiration
Structure and mechanism of a Hypr GGDEF enzyme that activates cGAMP signaling to control extracellular metal respiration
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DOI：
10.7554/elife.43959
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发表时间：
2019-04-09
期刊：
影响因子：
7.7
通讯作者：
Hammond, Ming C.
中科院分区：
文献类型：
--
作者：
Hallberg, Zachary F.;Chan, Chi Ho;Hammond, Ming C.
一个新发现的信号通路使用了一种GGDEF酶，与大多数与细菌环状双GMP信号相关的同源物相比，GGDEF酶具有独特的活性。这个系统提供了一个难得的机会来研究信号蛋白如何天然地获得不同的功能。利用基因敲除、核糖开关报告和RNA-Seq，我们证明了GacA，硫还原地杆菌中的Hypr GGDEF，在体内特异性地调节循环GMP-AMP(3‘，3’-cGAMP)水平，以刺激与金属还原相关的基因表达。为了将这些体内研究结果与先前显示GacA是混杂的体外结果相一致，我们开发了一个结合实验数据和数学模型的完整动力学模型，以揭示有助于体内特异性的机制。为了了解这些机制的分子基础，包括关键的交叉二聚体相互作用，我们确定了Gebacter Hypr GGDEF结构域的1.4埃分辨率晶体结构。总而言之，这些结果表明，特定的信号可能是由一种混杂的酶产生的。
A newfound signaling pathway employs a GGDEF enzyme with unique activity compared to the majority of homologs associated with bacterial cyclic di-GMP signaling. This system provides a rare opportunity to study how signaling proteins natively gain distinct function. Using genetic knockouts, riboswitch reporters, and RNA-Seq, we show that GacA, the Hypr GGDEF in Geobacter sulfurreducens, specifically regulates cyclic GMP-AMP (3',3'-cGAMP) levels in vivo to stimulate gene expression associated with metal reduction separate from electricity production. To reconcile these in vivo findings with prior in vitro results that showed GacA was promiscuous, we developed a full kinetic model combining experimental data and mathematical modeling to reveal mechanisms that contribute to in vivo specificity. A 1.4 angstrom-resolution crystal structure of the Geobacter Hypr GGDEF domain was determined to understand the molecular basis for those mechanisms, including key cross-dimer interactions. Together these results demonstrate that specific signaling can result from a promiscuous enzyme.