Defense Date


Document Type


Degree Name

Master of Science


Microbiology & Immunology

First Advisor

Cynthia Nau Cornelissen


Iron, an essential nutrient for most microorganisms, is sequestered in the host by iron-binding proteins, such as lactoferrin and transferrin. Neisseria gonorrhoeae utilizes transferrin as an iron source and its iron acquisition system is composed of two transferrin binding proteins: TbpA and TbpB. TbpA is a TonB-dependent, outer membrane transporter and TbpB is a bilobed, surface exposed lipoprotein. TbpB can distinguish between apo- and holo-transferrin which is involved in increasing the efficiency of iron uptake through the Tbps. It is anchored in the outer leaflet of the outer membrane by its lipid moiety. We aimed to identify the mechanism of TbpB export to the cell surface. No conclusions could be made from our results but we identified a protein that could potentially be involved in lipoprotein transport. TbpB is a bilobed protein with controversy over which lobe is involved in transferrin binding. In this study, we constructed a C-lobe deletion of TbpB to determine the role of the C-lobe in TbpB function. Results presented here showed deletion of the C-lobe caused degradation of TbpB and the minimal protein expressed was unable to bind transferrin both in vitro and in vivo. We were also able to demonstrate the TbpB C-lobe deletion is able to support limited transferrin-mediated growth, indicating some function of TbpB is retained. These results confirmed that both lobes are necessary for wild-type function of TbpB.


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Date of Submission

July 2012