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

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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.