All domains of life require zinc (II) (Zn) as an essential cofactor. To successfully infect its human host, the bacterium Neisseria gonorrhoeae must overcome nutritional immunity, a defense strategy in which the host restricts access to nutrient metals such as iron, manganese, and Zn. N. gonorrhoeae has evolved mechanisms to subvert host-mediated Zn limitation, including the ability to acquire Zn from human metal-sequestering proteins. To date, many genes important for N. gonorrhoeae growth under Zn-limited conditions remain uncharacterized. Among the most highly upregulated genes during Zn limitation is zcp, which encodes a protein belonging to the Domain of Unknown Function 4198 (DUF4198) family. Recent work by a collaborative team featuring the Cornelissen Lab at Georgia State University, Chazin Lab at Vanderbilt University, Noinaj Lab at Purdue University, and led by Alison Criss at the University of Virginia provides the first structural, biochemical, and functional characterization of the Zcp protein. Structural data obtained at GM/CA@APS revealed that Zcp forms a homodimer, with each subunit binding one Zn ion, coordinated by three histidine residues and a water molecule. Each monomer adopts a three-layer β-sandwich-like fold with two small peripheral α-helices. Functionally, Zcp is important for N. gonorrhoeae growth and infection under Zn-limited conditions. Zcp associates with proteins involved in maintaining bacterial cell envelope integrity, and N. gonorrhoeae lacking zcp show increased sensitivity to envelope-targeting antimicrobials. Collectively, these findings establish a role for the widespread family of DUF4198 proteins as metal-buffering substrate binding proteins that maintain Zn bioavailability for Zn-requiring proteins, forming part of the coordinated bacterial response to Zn limitation.
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Figure: The structure of Zn-bound Zcp from Neisseria gonorrhoeae. The dimer form of Zcp is shown in cartoon with individual subunits in green and purple. The zinc binding residues for each subunit are in ball and stick with zinc shown as a blue sphere. A zoomed view of the zinc binding site is shown in the middle panel. Tryptophan fluorescence (bottom left) and nano-differential scanning fluorimetry (bottom right) assays were used to characterize the binding of zinc to Zcp. |
Citation: Liyayi, IK, Bera, AK, Perera, YR, Ferdausi, N, Bhatia, I, Noinaj, N, Chazin, WJ, Cornelissen, CN, Criss, AK, "A periplasmic zinc capture protein enhances the resistance of Neisseria gonorrhoeae to nutritional immunity," Proc. Nat. Acad. Sci. USA 122 (47), e2426176122 (2025). DOI: 10.1073/pnas.2426176122.
GM/CA @ APS
