Structural caracterization and functional analysis of Nitrate/Nitrite transporter ABC type of Xanthomonas axonopodis pv. citri

Abstract

Xanthomonas citri is an aerobic bacteria that causes the citrus canker, a disease of plants that leads to significant economic losses in Brazil and worldwide. 4% of the genome of this bacterium encode ABC transporters, one of the largest families of proteins involved in different functions, ranging from transportation, nutrition, DNA repair to the phenomenon of multidrug resistance. Given the importance and involvement of these transporters in the physiology of organisms, they can be used as excellent targets for developing of inhibitors of bacterial growth. Despite its importance, the relationship of these carriers with the mechanisms of infection and pathogenesis in X. citri is not defined yet. In this context, this project aims to characterize structural and functional components of the ABC transporter-type nitrate/nitrite and taurine, encoded by the operon nitTnrtBCD. Since nitrate is the major source of nitrogen for organisms and their transport is extremely necessary, we believe that the carrier has a significant importance for the bacterium. Preliminary studies with a mutant of X. citri deleted for the nitT gene, which encodes the periplasmic binding protein, suggest a role of this protein in bacterial growth and infection. It is intended to structurally characterize all components of this transporter by spectroscopy, crystallography and molecular modeling, defining regions of protein-ligand and protein-protein interactions in order to establish possible targets for the development of inhibitors. Functionally, the analysis will be based on the construction of deletion mutants of the transporter genes and evaluation of the behavior of these in vitro assays in different growing conditions and in vivo during infection in the plant.