Functional and structural studies of the repressor protein PhoU in the phosphate transport signalling in Xanthomonas axonopodis pv. citri

Abstract

Phosphorus is the fourth most important element for cell growth and important in the biosynthesis of molecules, phosphorylation and energy production. In Escherichia coli its regulation is accomplished through the pho regulon, a set of sensing operons capable of encoding proteins, such as the two-component system PhoR/PhoB and the ATP-Binding Cassete proteins, such as the Pst system (Phosphate Specific Transport). Among the proteins of importance to the Pho regulon repressor is PhoU, which is related to the modulation of both systems, in a not clear mechanism. In order to further characterize this protein, studies have been conducted to solve its three-dimensional structure. However, there is no structural or functional data of PhoU from plant pathogens including the important Xanthomonas axonopodis pv. citri, the causative agent of the citrus canker and responsible for significant economic losses in Brazil and around the World. In recent work, our group has characterized the ABC transporter Pst and the two components system PhoR/PhoB and demonstrated their importance in the metabolism, infection and pathogenesis of X. citri in Citrus sinensis plants. Continuing these studies, this project aims to understand the PhoU function in X. citri through functional and structural characterization of this protein. It is intended to solve its three-dimensional structure by crystallography and evaluate the interaction with the protein kinase PhoR using biophysical and spectroscopic methods. (AU)