Ferric enterobactin binding and utilization by Neisseria gonorrhoeae

Area of Science:

• Microbiology
• Bacterial Physiology
• Molecular Biology

Background:

• FetA (FrpB) is an iron-regulated outer membrane protein in Neisseria species with homology to TonB-dependent receptors.
• Its specific function in Neisseria gonorrhoeae and Neisseria meningitidis physiology was previously unknown.
• FetA is a potential vaccine candidate for both pathogenic Neisseria.

Purpose of the Study:

• To determine the function of FetA in Neisseria gonorrhoeae iron acquisition.
• To investigate FetA's role in utilizing ferric enterobactin as an iron source.
• To characterize the interaction of FetA with enterobactin.

Main Methods:

• Genetic manipulation of the fetA and tonB genes in N. gonorrhoeae FA1090.
• Growth assays using ferric enterobactin as the sole iron source.
• Binding assays using 59Fe-enterobactin to measure FetA affinity.
• Western blot analysis using monoclonal antibodies against E. coli FepA.
• Sequence comparisons between FetA and FepA.

Main Results:

• N. gonorrhoeae FA1090 utilized ferric enterobactin for growth, dependent on functional fetA and tonB genes.
• FetA specifically bound ferric enterobactin with a dissociation constant (Kd) of approximately 5 microM.
• Monoclonal antibodies against E. coli FepA recognized FetA, indicating conserved epitopes.
• A downstream gene, fetB, predicted a periplasmic binding protein potentially involved in transport.
• Disruption of fetB abolished enterobactin utilization but not binding, suggesting a transport role.

Conclusions:

• FetA functions as a functional homolog of the E. coli enterobactin receptor FepA.
• FetA binds ferric enterobactin, indicating its role in siderophore-mediated iron uptake.
• FetA, along with FetB, likely constitutes a system for transporting enterobactin into Neisseria cells.