Transferrins bacterial

FhuA and FepA will prove to be the reference structures for a large group of bacterial outer-membrane transporters that take up bacterial Fe3+-siderophores, Fe3+ released from host transferrin and lactoferrin, haem, and haem released from haemoglobin and haemopexin. It is assumed that all iron sources are transported... 

The determination of the structure of the iron transporter, ferric-binding, protein (hFBP)t from Haemophilus influenzae (Bruns et ah, 1997) at 0.16 nm resolution shows that it is a member of the transferrin superfamily, which includes both the transferrins and a number of periplasmic binding proteins (PBP). The PBPs transport a wide variety of nutrients, including sugars, amino acids and ions, across the periplasm from the outer to the inner (plasma) membrane in bacteria (see Chapter 3). Iron binding by transferrins (see below) requires concomitant binding of a carbonate anion, which is located at the N-terminus of a helix. This corresponds to the site at which the anions are specifically bound in the bacterial periplasmic sulfate- and... 

Comelissen, C. N. and Sparling, P. F. (1994). Iron piracy acquisition of transferrin-bound iron by bacterial pathogens, Mol. Microbiol., 14, 843-850. 

Bacterial hosts are inappropriate choices for expression of proteins such as the blue copper proteins stellacyanin, laccase, and ceruloplasmin which are extensively glycosylated. In these cases, it may be necessary to employ tissue cultures of appropriate origin to obtain the native protein. In this regard, the amino-terminal half of human serum transferrin, which lacks carbohydrate, has been expressed in high yield in baby hamster kidney cells by Funk et al. [13], while the glycosylated carboxyl-terminus has proved to be more problematic [103]. 

The competition between transferrin and infectious organisms is a fascinating topic. During infection, the mammalian host will attempt to diminish the iron available to the bacterium. The iron levels in the blood decrease and the iron stores in the liver increase. The observation that siderophore synthesis is sharply reduced at temperatures just over 37 °C may mean that the physiological function of fever is to depress bacterial siderophore synthesis, as shown for a rabbit pathogen, Pseudomonas multocida.1203... 

The iron complexes of both human serum transferrin and chicken ovo-transferrin were completely resistant to all proteolytic enzymes tested (7). The metal-free proteins, on the other hand, were rapidly hydrolyzed under similar conditions. Fig. 14 compares results with bovine a-chymo-trypsin. Other enzymes used with similar results were bovine trypsin, bacterial proteinase (Nagarse) and ficin (735). The weaker copper complex of chicken ovotransferrin was hydrolyzed, however, at a rate approx-... 

I, 2, and 3 are correct. Haptoglobin removes hemoglobin, and transferrin mops up Fe3+ and even Fe. These can increase bacterial virulence if not rapidly sequestered. Ferritin is not associated with antibacterial action. 

Fig. 2. Possible evolutionary development of the transferrin family, showing also the proposed relationship of bacterial periplasmic binding proteins (Section III.D).

A remarkable feature of transferrin structure, discovered when the human lactoferrin structure was determined (67, 85), is the striking similarity with a group of bacterial binding proteins. These proteins, the bacterial periplasmic binding proteins, bind and transport certain small molecules, such as sugars, amino acids and oxyanions, through the periplasmic space before delivering them via specific receptors in the bacterial cell wall (111). They thus share with transferrins the... 

Fig. 15. Polypeptide folding patterns for (a) one-half of a transferrin molecule (the N-lobe of lactoferrin) and (b) the bacterial periplasmic sulfate-binding protein. Adapted from Baker et al. (85), with permission.

As noted in Section 3, some pathogenic bacteria have transferrin receptors on their outer membranes to acquire diferric transferrin from their host. These outer membrane receptors extract the iron from the transferrin and transport it into the periplasm where it is picked up by the periplasmic ferric binding proteins (Fbp), which carry the iron to a transmembrane protein in the inner membrane that conveys it into the cytoplasm. A considerable amount of chemical and structural information has been gathered for Fbp, which is sometimes referred to as bacterial transferrin in recognition of its similarities with animal transferrin. ... 

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