Regulation of gvp gene expression in halophilic archaea

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The formation of gas vesicles in archaea is influenced by environmental factors such as light, oxygen tension and the salt concentration of the medium. Our aim is to understand the regulation of gas vesicle formation in Halobacterium salinarum and Haloferax mediterranei at the level of the promoters and the regulatory proteins, but also at the level of the mRNA and translation. The promoter of the gvpA gene encoding the major structural protein GvpA that is activated by GvpE, whereas GvpD and possibly GvpF appear to be involved in the repression. The interaction of GvpE and GvpD will be analysed in detail. It is possible that GvpD influences the activity of GvpE by proteinprotein interaction and/or phosphorylation. Using the bgaH reading frame encoding a halobacterial b-galactosidase as reporter, the gvp promoters will be studied in vivo to investigate the functions of the TATA-box and the BRE-element for the basal transcription and also the regions required for the GvpE-mediated activation. The mcA and pA promoters appear to be regulated by salt, and we will define the sequences involved. Finally, the contribution of non-translated mRNAs regions (including hairpin loop structures) to transcript termination and/or transcript stability will be investigated.