X. citri is a pathogen of great interest because it is responsible for the development of citrus canker in plants. Much effort has been performed to characterize the mechanisms that affect the growth, infection and pathogenesis, but little is known about the metabolism of this bacterium in relation to the uptake of ions, and in particular the metabolism of sulfur. In recent studies performed by our group (FAPESP 2010/14207-8) have identified and functionally characterized proteins belonging to the sulfate uptake and reduction to sulfide ions, which include an ABC-type transporter system consisting of the periplasmic binding protein Spb, two permeases (CysWU) and two ATPases (CysA), and the enzymes CysNCD, CysIJH and CysG. In a study conducted by our group it was demonstrated that this pathway is complete in X. citri and it is activated during growth in M9 minimal medium and rich medium LB. Additionally, activation of the operon encoding the ABC transporter was fully demonstrated in vitro and in vivo, indicating the importance of this transporter during growth and infection of bacteria in Citrus sinensis (orange pear). Thus, this work aims to further characterize the mechanism of transport of sulfate through structural and functional studies of the type ABC transporter, specifically, the periplasmic-binding protein Sbp, the membrane components and the ATPases. The target proteins will be expressed and purified for studies of interaction with sulfate, protein-protein interactions and structural analysis by crystallography. Additionally, the relevance of this transporter during the growth of bacteria and infection will be evaluated using mutants of X. citri with a deletion in the gene sbp (Xac1017). This will be a pioneering work on the characterization of the importance of sulfate ABC transporter to X. citri indicating possible targets for the development of inhibitors. Additionally, the structural components of this transporter, which involves two membrane proteins, will greatly impact on the scientific community and will be of great importance for studies of ion uptake in bacteria.
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