Structural biochemistry of c-di-AMP degrading phosphodiesterases and their regulation

核苷酸第二信使是将外部/内部信号与细胞的细胞应答联系起来的信号转导事件的关键组分。c-di-AMP作为一种新的细菌第二信使的发现开辟了细菌信号转导的新领域。虽然c-di-AMP途径中的一组蛋白质已经被表征，但c-di-AMP调节过程中蛋白质和连接性的相互作用仍不清楚。由于c-di-AMP是必不可少的（对于合成它的细菌），并且c-di-AMP水平的变化对细胞有显著影响，改变c-di-AMP的浓度可能是抗菌治疗的潜在目标。我们的目的是分析降解的c-di-AMP的特定磷酸二酯酶（PDE）携带DHH-DHHA 1结构域，负责水解的环二核苷酸。有趣的是，已经描述了这些DHH型PDE的两个亚家族，一个膜蛋白型（GdpP）还具有另外的调节结构域（GGDEF和PAS），一个胞质PDE仅包含DHH-DHHA 1结构域。第一组将c-di-AMP降解为5-pApA，而后者能够将c-di-AMP和5-pApA降解为AMP。我们的目标是使用生物化学，生物物理和结构的方法（支持在体内的方法），以阐明这两种类型的PDE的结构功能关系。我们将试图确定两个DHH型PDE之间的结构差异，导致不同的产品，也试图阐明GdpP型PDE的调节其附属结构域（GGDEF和PAS）。

Nucleotide second messengers are key components of signal transduction events that link external/internal signals to the cellular response of the cell. The discovery of c-di-AMP as a new and also essential bacterial second messenger opened up a new field in bacterial signaling. Whereas a set of proteins in the c-di-AMP pathway has been already been characterized, the interplay of proteins and connectivity in the c-di-AMP regulatory processes is yet still unclear. Due to the fact that c-di-AMP is essential (for the bacteria synthesizing it) and the fact that changes in the c-di-AMP level have dramatic effect on the cells, altering the concentration of c-di-AMP might be a potential target in antimicrobial therapy. We aim to analyze the degradation of c-di-AMP by specific phosphodiesterases (PDE) carrying a DHH-DHHA1-domain that is responsible for the hydrolysis of the cyclic dinucleotide. Interestingly, two subfamilies of these DHH-type PDE have been described, one membrane protein-type (GdpP) possessing also additional regulatory domains (GGDEF and PAS) and one cytosolic PDE only comprising the DHH-DHHA1-domain. Whereas the first group degrades c-di-AMP to 5-pApA, the latter is able to degrade both c-di-AMP but also 5-pApA to AMP. We aim to use biochemical, biophysical and structural methods (supported by in vivo methods) to elucidate the structure function relationship of these two types of PDEs. We will try to identify the structural differences between the two DHH-type PDEs leading to different products and also try to shed light on the regulation of GdpP-type PDEs by its accessory domains (GGDEF and PAS).