Molecular interaction and high-resolution X-ray structures of the subunits of the osmoregulated ABC-transporter OpuA from B. subtillis

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The osmoprotectant uptake system OpuA is one of the three osmoprotective transporters in Bacillus subtilis, which mediate the uptake of the compatible solute glycine betaine, an osmoprotectant widely used by bacteria, plants and even human cells. The transporter complex consists of a lipid-anchored substrate-binding protein (OpuAC), an integral transmembrane protein (OpuAB), and an ATPase subunit (OpuAA) and belongs to the super family of ABC-transporters. In recent years, the osmoprotective transporter complex OpuA has been intensively characterized on a genetic and physiological level. However, no in vitro studies have been performed including structural, biochemical or biophysical studies. Based on our biochemical studies performed so far, we propose to study this transporter complex with respect to its structure and the dynamic aspects of the communication between the subunits within the complex. In vitro and in vivo experiments with the OpuA system will accompany our structural investigations. For the in vitro experiments, crystallography, surface plasmon resonance, and fluorescence techniques will be of major importance. These studies will be aided by in vivo experiments using already available deletion strains of the osmo-regulated transporter systems of B. subtilis. Based on the proposed experiments, we hope to provide a detailed understanding of the structural requirements and communication mechanisms governing the function of the OpuA ABC-transporter of B. subtilis.