Figure 6

Proposed model of Zn²⁺ acquisition in P. aeruginosa PAO1.

Schematic representation of the Zn²⁺ acquisition pathways of P. aeruginosa PAO1 based on transcriptomic and biochemical analyses. Under Zn²⁺-replete conditions, dimeric Zur, the primary Zn²⁺-responsive regulator, binds Zn²⁺, thereby repressing transcription of the Zn²⁺ import pathways. Zinc limitation facilitates the dissociation of Zn²⁺ from Zur, thereby permitting de-repression of the Zn²⁺ uptake pathway genes. Zinc entry into the periplasm occurs via four TonB-dependent outer membrane proteins: ZnuD (PA0781), PA2911, PA1922 and PA4837. Within the periplasm, Zn²⁺-specific SBPs (ZnuA, PA2913, PA4063 and PA4066) likely bind Zn²⁺, either as the free ion or chelated Zn²⁺ and deliver it to a cognate ABC import system (ZnuBC, PA2912/PA2914 and PA4064/PA4065), which facilitates vectorial transport to the cytosol. In addition, HmtA, a P-type ATPase is also able to import periplasmic Zn²⁺ ions into the cytoplasm.