Two-component systems (TCSs) are a major class of bacterial signal-transduction pathways that enable adaptation to fluctuating environmental conditions. The Zra system is a specialised TCS involved in zinc homeostasis in Escherichia coli and Klebsiella pneumoniae. Classical TCSs consist of a sensor kinase (SK) and a response regulator (RR). However, the Zra system uniquely incorporates an additional periplasmic protein, ZraP. In Salmonella enterica, ZraP has been reported to function both as a molecular chaperone and as a repressor of Zra signalling1. In contrast, the structural features and functional roles of ZraP in E. coli and K. pneumoniaeremain unknown, limiting the mechanistic understanding of the whole Zra system.
This project aims to determine the structures of ZraP from K. pneumoniae (KpZraP) and E. coli(EcZraP) using X-ray crystallography, and to characterize their binding affinities for Zn²+. Thereby, these results will clarify the role of ZraP in bacterial zinc homeostasis and stress adaptation.