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Infection and Immunity, July 2007, p. 3220-3232, Vol. 75, No. 7
0019-9567/07/$08.00+0     doi:10.1128/IAI.00072-07
Copyright © 2007, American Society for Microbiology. All Rights Reserved.

Identification of Transferrin-Binding Domains in TbpB Expressed by Neisseria gonorrhoeae{triangledown}

Amanda J. DeRocco and Cynthia Nau Cornelissen*

Department of Microbiology and Immunology, Virginia Commonwealth University Medical Center, Richmond, Virginia 23298-0678

Received 12 January 2007/ Returned for modification 7 March 2007/ Accepted 9 April 2007

The transferrin iron acquisition system of Neisseria gonorrhoeae is necessary for iron uptake from transferrin in the human host and requires the participation of two distinct proteins: TbpA and TbpB. TbpA is a TonB-dependent outer membrane transporter responsible for the transport of iron into the cell. TbpB is a lipid-modified protein, for which a precise role in receptor function has not yet been elucidated. These receptor complex proteins show promise as vaccine candidates; therefore, it is important to identify surface-exposed regions of the proteins required for wild-type functions. In this study we examined TbpB, which has been reported to be surface exposed in its entirety; however, this hypothesis has never been tested experimentally. We placed the hemagglutinin (HA) epitope into TbpB with the dual purpose of examining the surface exposure of particular epitopes as well as their impact on receptor function. Nine insertion mutants were created, placing the epitope downstream of the signal peptidase II cleavage site. We report that the HA epitope is surface accessible in all mutants, indicating that the full-length TbpB is completely surface exposed. By expressing the TbpB-HA fusion proteins in N. gonorrhoeae, we were able to examine the impact of each insertion on the function of TbpB and the transferrin acquisition process. We propose that TbpB is comprised of two transferrin-binding-competent lobes, both of which are critical for efficient iron uptake from human transferrin.

* Corresponding author. Mailing address: Department of Microbiology and Immunology, Virginia Commonwealth University Medical Center, P.O. Box 980678, Richmond, VA 23298-0678. Phone: (804) 827-1754. Fax: (804) 828-9946. E-mail: cncornel{at}vcu.edu

{triangledown} Published ahead of print on 16 April 2007.

Editor: D. L. Burns

Infection and Immunity, July 2007, p. 3220-3232, Vol. 75, No. 7
0019-9567/07/$08.00+0     doi:10.1128/IAI.00072-07
Copyright © 2007, American Society for Microbiology. All Rights Reserved.





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