Human lactoferrin

Aguas, A., Esaguy, N., Sunkel, C.E., Silva, M.T. (1990). Cross-reactivity and sequence homology between the 65 kilodalton mycobacterial heat shock protein and human lactoferrin, transferrin, and DR beta subsets of major histocompatibility complex class II molecules. Infect. Immun. 58, 1461-1470. 

Van Berkel, P.H., Welling, M.M., Geerts, M. et al. (2002) Large scale production of recombinant human lactoferrin in the milk of transgenic cows. Nature Biotechnology, 20 (5), 484—487. 

Figure 5.5 Stereo view of the Fe3+ binding site of (a) hFBP (b) human lactoferrin, N-lobe and (c) human transferrin (N-lobe). From Bruns, 1997. Reproduced by permission of Nature Publishing Group. 

Determination of the amino-acid sequence of human serum transferrin (MacGillivray et ah, 1983) and of human lactoferrin (Metz-Boutique etal., 1984) revealed an internal two-fold sequence repeat. The amino-terminal half has approximately 40 % sequence identity with the carboxyl-terminal half. Similar results have subsequently been found for a number of other transferrins (Baldwin,... 

Figure 5.1 Schematic diagram of the lactoferrin molecule. The positions of carbohydrate attachment are marked with a star. O, ovotransferrin T, human serotransferrin L, human lactoferrin R, rabbit serotransferrin M, melanotransferrin A, the connecting helix B, the C-terminal helix. The disulfide bridges are indicated by heavy bars, and the iron and carbonate binding sites by filled or open circles, respectively. Reprinted from Baker et al., 1987. Copyright (1987), with permission from Elsevier Science.

Figure 5.2 Schematic representation of the folding pattern for the N-lobe (left) and C-lobe (right) of human lactoferrin. From Anderson et al., 1989. Reproduced by permission of Academic Press.

The iron-binding sites have been characterized by crystallographic studies on several transferrins, and in Figure 5.7 (Plate 7) that of the N-lobe of human lactoferrin is presented. The 3+ charge on the ferric ion is matched by the three anionic ligands Asp-63, Tyr-95 and Tyr-188 (the fourth, His-249, is neutral), while the charge on the carbonate anion is almost matched by the positive charge on Arg-124 and the... 

Figure 5.8 A schematic representation of the N-lobe polypeptide chain fold, showing the conformational change between open and closed forms of human lactoferrin. Reprinted with permission from Nature (Anderson et ah, 1990). Copyright (1990) Macmillan Magazines Limited.

Nithipatikom, K., and McGown, L.B. (1987) Homogeneous immunochemical technique for determination of human lactoferrin using excitation tranfer and phase-resolved fluorometry. Anal. Chem. 59, 423. 

Hakansson, A., Roche, H., Mirza, S., McDaniel, L. S., Brooks-Walter, A. and Briles, D. E. (2001). Characterization of binding of human lactoferrin to pneumococcal surface protein A, Infect. Immun., 69, 3372-3381. 

Arnold RR, Cole MF, McGhee JR (1977) A bactericidal effect for human lactoferrin. Science 197(4300) 263-265. 

Plaut, A. G., Qiu, J., and St, G. J., III. (2000). Human lactoferrin proteolytic activity Analysis of the cleaved region in the IgA protease of Haemophilus influenzae. Vaccine 19(Suppl. 1), S148-S152. 

Zhang, G. H., Mann, D. M., and Tsai, C. M. (1999). Neutralization of endotoxin in vitro and in vivo by a human lactoferrin-derived peptide. Infect. Immun. 67,1353-1358. 

Figure 20. Top left Condensed schematic diagram of human lactoferrin (hLf), with the C-lobe shown on the right and the N-lobe on the left. The a-carbons of cysteine and selected noncysteine residues are symbolized by filled and open circles, respectively. Cystine cross-links are shown as dashed lines. Unlabeled vertices symbolize carbon atoms, and hydrogen atoms are suppressed for clarity. Top right The trefoil knot derived from the C-lobe of hLf. Bottom Stereoview (Ca trace plus cross-links) of the knot shown on the top right.93 Reprinted with permission from C. Liang and K. Mislow, J. Am. Chem. Soc. 1995,117,4201. Copyright, 1995 American Chemical Society.

Fig. 15.2 Levels of targeting endotoxin (BP binding-protein BPI bactericidal/permeability increasing protein HLF human lactoferrin PMX-HF polymyxin B hemoperfusion)...

Human lactoferrin (HL) is a component of innate immunity. Human lactoferrin is an iron-binding protein found in milk, granulocytes and exocrine secretions. It is released during inflammation, has bactericidal effects and reduces cytokine production by binding to the lipid A portion of endotoxin (Appelmelk et al., 1994). 

Tani, F., Iio, K., Chiba, H., and Yoshikawa, M. 1990. Isolation and characterization of opioid antagonist peptides derived from human lactoferrin. Agric. Biol. Chem. 54, 1803-1810. 

Qian, Z.Y., Jolles, P., Migliore-Samour, D., and Fiat, A.M. 1995. Isolation and characterization of sheep lactoferrin, an inhibitor of platelet aggregation and comparison with human lactoferrin. Biochim. Biophys. Acta 1243, 25-32. 

Smith CA, Sutherland-Smith AJ, Keppler BK, Kratz F, Baker EN (1996) Binding of ruthenium(III) anti-tumor chugs to human lactoferrin probed by high resolution X-ray crystallographic structure analyses. J Biol Inorg Chem 1 424 -31... 

The large size of transferrins (670-700 residues), with the consequent difficulties of chemical sequencing, meant that it was not until 1982 that the first amino acid sequences, those of human serum transferrin 10) and chicken ovotransferrin 34,35), were established. These were closely followed by that of human lactoferrin 11). The twofold internal repeat in each sequence (see below) was immediately apparent, and comparison of all three sequences then identified conserved tyrosines and histidines that were potential ligands for iron (11). 

The first crystallographic studies on transferrins date back more than 20 years (58), and crystals of various transferrins have since been reported. These include the diferric forms of rabbit (59) and human (60) serum transferrins, hen (61) and duck (62) ovotransferrins, human (63) and bovine (64) lactoferrins, and the apo- (iron free) forms of human lactoferrin (65) and duck ovotransferrin (62). In spite of all this activity, the crystals in many cases have proved difficult to handle, and the X-ray analyses quite challenging. A low-resolution analysis of rabbit serum transferrin in 1979 demonstrated the bilobal nature of the molecule (66), but it was not until 1987, with the publication of the structure of human lactoferrin (67), that full details of a transferrin... 

Complementing the structural studies of the intact transferrins, a number of fragments have also been crystallized, including proteolytic N-terminal half-molecules of rabbit serum transferrin (69) and chicken ovotransferrin (70), recombinant N-terminal half-molecules of human lactoferrin (71) and human serum transferrin (72), and a quarter-molecule fragment of duck ovotransferrin (73). All of these have now led to high-resolution structures (74-77). 

The most detailed description of a complete transferrin molecule is that of human lactoferrin, at 2.8-A resolution (78), and most of the data in the following sections come from this work and from refinement of the same structure at 2.1-A resolution (79). As would be expected from the high level of sequence similarity, the three-dimensional structure of rabbit serum transferrin (68), although at lower resolution (3.3 A), is completely consistent with that of lactoferrin the differences are at the level of individual amino acid changes, together with some differences in lobe and domain orientations. These are discussed below (Section III.B.l). 

Coordinates for human lactoferrin, in both diferric (78) and apo- (80) forms, for diferric rabbit serum transferrin (68), and for the three fragment structures, the proteolytic N-lobe of rabbit serum transferrin (74), the recombinant N-lobe of human lactoferrin (75) and the duck ovotransferrin quarter-molecule (76), all in their iron-bound forms, can be obtained from the Brookhaven Protein Data Bank (Brookhaven National Laboratory, Upton, New York). 

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