The transferrin–iron import system from pathogenic <i><scp>N</scp>eisseria</i> species

Noinaj, Nicholas; Buchanan, Susan K.; Cornelissen, Cynthia Nau

doi:10.1111/mmi.12002

Cited by 68 publications

(71 citation statements)

References 53 publications

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“…Studies on the gonococcal transferrin receptor have focused mainly on deciphering the structure-function relationships of its components (19,20), and little is known about the precise mechanisms that coordinately control expression of these proteins. A…”

Section: Discussionmentioning

confidence: 99%

“…TbpA is capable of transporting iron across the outer membrane of gonococci, making it essential in the process of iron uptake from transferrin (19,20). TbpB is a surface-exposed lipoprotein (19,20) that has the ability to discriminate between holo-and apotransferrin (21,22). Expression of TbpA is essential for uptake of iron (18), and although expression of TbpB is not essential, its presence makes the iron uptake process more efficient (17).…”

mentioning

confidence: 99%

“…TbpA is an integral outer membrane protein which shares sequence similarity with TonB-dependent outer membrane transporters (18). TbpA is capable of transporting iron across the outer membrane of gonococci, making it essential in the process of iron uptake from transferrin (19,20). TbpB is a surface-exposed lipoprotein (19,20) that has the ability to discriminate between holo-and apotransferrin (21,22).…”

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confidence: 99%

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Identification of Regulatory Elements That Control Expression of the tbpBA Operon in Neisseria gonorrhoeae

et al. 2014

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Iron is an essential nutrient for survival and establishment of infection by Neisseria gonorrhoeae. The neisserial transferrin binding proteins (Tbps) comprise a bipartite system for iron acquisition from human transferrin. TbpA is the TonB-dependent transporter that accomplishes iron internalization. TbpB is a surface-exposed lipoprotein that makes the iron uptake process more efficient. Previous studies have shown that the genes encoding these proteins are arranged in a bicistronic operon, with the tbpB gene located upstream of tbpA and separated from it by an inverted repeat. The operon is under the control of the ferric uptake regulator (Fur); however, promoter elements necessary for regulated expression of the genes have not been experimentally defined. In this study, putative regulatory motifs were identified and confirmed by mutagenesis. Further examination of the sequence upstream of these promoter/operator motifs led to the identification of several novel repeats. We hypothesized that these repeats are involved in additional regulation of the operon. Insertional mutagenesis of regions upstream of the characterized promoter region resulted in decreased tbpB and tbpA transcript levels but increased protein levels for both TbpA and TbpB. Using RNA sequencing (RNA-Seq) technology, we determined that a long RNA was produced from the region upstream of tbpB. We localized the 5= endpoint of this transcript to between the two upstream insertions by qualitative RT-PCR. We propose that expression of this upstream RNA leads to optimized expression of the gene products from within the tbpBA operon.

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Section: Discussionmentioning

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Identification of Regulatory Elements That Control Expression of the tbpBA Operon in Neisseria gonorrhoeae

et al. 2014

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“…To take up iron from the host ironbinding proteins transferrin and lactoferrin, bacteria express specific outer membrane receptors. Upon binding to the receptor, iron is released and transported through the receptor to the periplasmic space and subsequently to the cytoplasm (6,7). Bacteria can also obtain iron from red blood cells via similar though more complex mechanisms.…”

Section: Introductionmentioning

confidence: 99%

Plasmid-Encoded Iron Uptake Systems

Lorenzo

Stork

2014

Microbiol Spectr

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Plasmids confer genetic information that benefits the bacterial cells containing them. In pathogenic bacteria, plasmids often harbor virulence determinants that enhance the pathogenicity of the bacterium. The ability to acquire iron in environments where it is limited, for instance the eukaryotic host, is a critical factor for bacterial growth. To acquire iron, bacteria have evolved specific iron uptake mechanisms. These systems are often chromosomally encoded, while those that are plasmid-encoded are rare. Two main plasmid types, ColV and pJM1, have been shown to harbor determinants that increase virulence by providing the cell with essential iron for growth. It is clear that these two plasmid groups evolved independently from each other since they do not share similarities either in the plasmid backbones or in the iron uptake systems they harbor. The siderophores aerobactin and salmochelin that are found on ColV plasmids fall in the hydroxamate and catechol group, respectively, whereas both functional groups are present in the anguibactin siderophore, the only iron uptake system found on pJM1-type plasmids. Besides siderophore-mediated iron uptake, ColV plasmids carry additional genes involved in iron metabolism. These systems include ABC transporters, hemolysins, and a hemoglobin protease. ColV-and pJM1-like plasmids have been shown to confer virulence to their bacterial host, and this trait can be completely ascribed to their encoded iron uptake systems.

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“…After binding, they are activated by interaction with energy-transducing TonB (24,25). The result is changes in conformation of both the Tf receptor and Tf (26). Iron is released from Tf and is then imported through an interior channel in TbpA to the periplasm and eventually into the cell.…”

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confidence: 99%