Osmoregulatory transport of compatible Solutes in Bacteria: Structure, function and regulation of the TRAP Transporter TeaABCD from Halomonas elogata

在嗜盐细菌长盐单胞菌中，外托因的摄取是由trap转运体TeaABC催化的。trap转运蛋白是一类新的、独特的二级转运蛋白。没有关于trap转运体的结构信息。TeaABC是第一个在嗜盐细菌中发现的相容溶质转运蛋白，也是第一个属于TRAP-T家族的渗透调节转运蛋白。敲除TeaABC产生一个突变体，该突变体将外泌素排泄到培养基中，TeaABC的生理作用不仅是在细胞内积累外源性外泌素，而且可以通过细胞质膜恢复外源性外泌素。没有关于相容溶质如何离开电池的信息。据推测，特定的通道参与了相容溶质的输出，如异托宁。提出的研究目标是解决TeaABC的单个组件和整个TeaABC复合物的结构，并了解这些组件如何协同工作。进一步分析了TeaABC的渗透调节激活及其在酶活性水平上的渗透感应机制。最后，本研究将重点关注外泌素的外排，以及TeaABC对外泌素外排和外泌素恢复的调控作用。它的目的是确定和描述假定的出口系统。

In the halophilic bacterium Halomonas elongata, uptake of ectoines is catalyzed by the TRAP-transporter TeaABC. TRAP-transporters form a new and unique class of secondary transporters. No structural information is available on TRAP-transporters. TeaABC is first compatible solute transporter identified in a halophilic bacterium and it is the first osmoregulated transporter belonging to the TRAP-T family. Knock out of TeaABC creates a mutant, which excretes ectoine to the medium and the physiological role of TeaABC is not only to accumulate external ectoine in the cell but also to recover endogenous ectoine leaking through the cytoplasmic membrane. No information is available on how compatible solutes are leaving the cell. It is assumed that specific channels are involved in the export of compatible solutes such as ectoine. The goal of the proposed research is to resolve the structure of the single components of TeaABC and the whole TeaABC complex and to understand how these components work together. Furthermore, the osmoregulatory activation of TeaABC and the osmosensing mechanism at the level of enzyme activity will be analyzed. Finally, the research will focus on the efflux of ectoine, and the proposed regulatory interaction of ectoine efflux and ectoine recovery by TeaABC. It is intended to identify and characterize the putative export system(s) for ectoines.