A Zur-mediated transcriptional regulation of the zinc export system

Abstract

AbstractThe control of cellular zinc (Zn) concentrations by dedicated import and export systems is essential for the survival and virulence ofPseudomonas aeruginosa. The transcription of its many Zn transporters is therefore tightly regulated by a known set of transcription factors involved in either the import or the export of Zn. In this work, we show that the Zur protein, a well-known repressor of Zn import, plays a dual role and functions in both import and export processes. In a situation of Zn excess, Zur represses Zn entry, but also activates the transcription ofczcR, a positive regulator of the Zn export system. To achieve this, Zur binds at two sites, located by DNA footprinting in the region downstream theczcRtranscription start site. In agreement with this regulation, a delay in induction of the efflux system is observed in the absence of Zur and Zn resistance is affected. The discovery of this regulation highlights a new role of Zur as global regulator of Zn homeostasis inP. aeruginosadisclosing an important link between Zur and zinc export.