A periplasmic zinc capture protein enhances the resistance of <i>Neisseria gonorrhoeae</i> to nutritional immunity.

Abstract

During microbial infection, mammalian hosts reduce the availability of free metals such as zinc in a process known as nutritional immunity. Pathogens counteract nutritional immunity by expressing gene products that enhance growth in metal-limited conditions. One of the most transcriptionally induced genes in zinc-limited <i><i>Neisseria</i> gonorrhoeae</i>, <i>ngo1049,</i> encodes a DUF4198 family protein we have named Zcp. This family of proteins is widely distributed in Gram-negative bacteria. Here, we provide the first structural, biochemical, and functional characterization of a DUF4198 protein. Zcp is a periplasmic, homodimeric substrate-binding protein (SBP), which binds one zinc ion per subunit with submicromolar affinity. We identified a zinc binding pocket in each subunit, composed of three histidine residues. Zcp enables maximal growth of <i>N. gonorrhoeae</i> in zinc-limited conditions but is dispensable for zinc uptake, in contrast to the cluster A-I SBP ZnuA, which is required for zinc import. The growth defect of <i>zcp</i> mutant <i>N. gonorrhoeae</i> is rescued by zinc supplementation. Zcp associates with proteins with roles in maintaining cell envelope integrity, and <i>N. gonorrhoeae</i> lacking <i>zcp</i> is more sensitive to envelope-targeting antimicrobials. Zcp enables infectivity of human epithelial cells and neutrophils by zinc-limited <i>N. gonorrhoeae</i>. We conclude that <i>N. gonorrhoeae</i> produces Zcp to buffer periplasmic zinc, which enables ZnuA to balance import of different metals and ensures the bioavailability of zinc for extracytoplasmic zinc-requiring proteins, as part of the coordinated response to host-imposed nutritional immunity.