Expression of chimeric human transferrin genes in vitro

1990 ◽  
Vol 27 (4) ◽  
pp. 633-641 ◽  
Author(s):  
K. Fischbach ◽  
Y. Lu ◽  
E. Tiffany-Castiglioni ◽  
A. Minter ◽  
B. H. Bowman ◽  
...  
Keyword(s):  
Diabetes ◽  
1985 ◽  
Vol 34 (5) ◽  
pp. 462-470 ◽  
Author(s):  
K. A. Ney ◽  
J. J. Pasqua ◽  
K. J. Colley ◽  
C. E. Guthrow ◽  
S. V. Pizzo
Keyword(s):  

2002 ◽  
Vol 70 (5) ◽  
pp. 2549-2558 ◽  
Author(s):  
Ann E. Jerse ◽  
Emily T. Crow ◽  
Amy N. Bordner ◽  
Ishrat Rahman ◽  
Cynthia Nau Cornelissen ◽  
...  

ABSTRACT Neisseria gonorrhoeae is capable of utilizing a variety of iron sources in vitro, including human transferrin, human lactoferrin, hemoglobin, hemoglobin-haptoglobin complexes, heme, and heterologous siderophores. Transferrin has been implicated as a critical iron store for N. gonorrhoeae in the human male urethra. The demonstration that gonococci can infect the lower genital tracts of estradiol-treated BALB/c mice in the absence of human transferrin, however, suggests that other usable iron sources are present in the murine genital tract. Here we demonstrate that gonococcal transferrin and hemoglobin receptor mutants are not attenuated in mice, thereby ruling out transferrin and hemoglobin as essential for murine infection. An increased frequency of phase variants with the hemoglobin receptor “on” (Hg+) occurred in ca. 50% of infected mice; this increase was temporally associated with an influx of neutrophils and detectable levels of hemoglobin in the vagina, suggesting that the presence of hemoglobin in inflammatory exudates selects for Hg+ phase variants during infection. We also demonstrate that commensal lactobacilli support the growth of N. gonorrhoeae in vitro unless an iron chelator is added to the medium. We hypothesize that commensal lactobacilli may enhance growth of gonococci in vivo by promoting the solubilization of iron on mucosal surfaces through the production of metabolic intermediates. Finally, transferrin-binding lipoprotein (TbpB) was detected on gonococci in vaginal smears, suggesting that although gonococci replicate within the genital tracts of mice, they may be sufficiently iron-stressed to express iron-repressible proteins. In summary, these studies support the potential role of nontransferrin, nonhemoglobin iron sources during gonococcal infection of the female genital tract.


Author(s):  
Billy K. -C. Chow ◽  
Walter D. Funk ◽  
David K. Banfield ◽  
Janet A. Lineback ◽  
Anne B. Mason ◽  
...  

1990 ◽  
Vol 189 (1) ◽  
pp. 1-5 ◽  
Author(s):  
Dieter Berger ◽  
Martina Winter ◽  
Hans G. Berger

2008 ◽  
Vol 92 (3) ◽  
pp. 537-542 ◽  
Author(s):  
W. WOITH ◽  
I. NÜSSLEIN ◽  
C. ANTONI ◽  
D. I. DEJICA ◽  
T. H. WINKLER ◽  
...  

1992 ◽  
Vol 70 (8) ◽  
pp. 636-642 ◽  
Author(s):  
Wei-Li Hu ◽  
Paul A. Chindemi ◽  
Erwin Regoeczi

Production of rat transferrin containing a single hybrid glycan was induced by treating rats with swainsonine, an inhibitor of α-mannosidase II. The principal component of this variant transferrin containing one sialic acid residue per mole of protein was separated from other forms of transferrin by anion-exchange chromatography, followed by lectin affinity chromatography. Transferrin bearing the hybrid glycan was degraded in vivo with a half-life of 14 h as compared with 40 h for transferrin containing a standard diantennary glycan. By using 125I-labelled tyramine-cellobiose, a label whose discharge from lysosomes is strongly retarded, organs rich in reticuloendothelial elements (liver, bone marrow, lungs, and spleen) were identified as the major sites of catabolism of the transferrin variant. The liver took up more 59Fe from the variant (26% of the dose in 90 min) than from control rat transferrin (12%). The excess iron uptake was reduced by the intravenous injection of either human transferrin or ovalbumin, and it was abolished by administering both. Macrophages from bone marrow and lungs degraded the transferrin variant in vitro. The degradation was significantly enhanced when transferrin receptors were blocked by human transferrin, and it was significantly reduced by ovalbumin and methyl glucopyranoside.Key words: glycoprotein, iron metabolism, lectin, plasma protein metabolism, transferrin.


Microbiology ◽  
2011 ◽  
Vol 157 (1) ◽  
pp. 209-219 ◽  
Author(s):  
Magda Reyes-López ◽  
Rosa María Bermúdez-Cruz ◽  
Eva E. Avila ◽  
Mireya de la Garza

Transferrin (Tf) is a host glycoprotein capable of binding two ferric-iron ions to become holotransferrin (holoTf), which transports iron in to all cells. Entamoeba histolytica is a parasitic protozoan able to use holoTf as a sole iron source in vitro. The mechanism by which this parasite scavenges iron from holoTf is unknown. An E. histolytica holoTf-binding protein (EhTfbp) was purified by using an anti-human transferrin receptor (TfR) monoclonal antibody. EhTfbp was identified by MS/MS analysis and database searches as E. histolytica acetaldehyde/alcohol dehydrogenase-2 (EhADH2), an iron-dependent enzyme. Both EhTfbp and EhADH2 bound holoTf and were recognized by the anti-human TfR antibody, indicating that they correspond to the same protein. It was found that the amoebae internalized holoTf through clathrin-coated pits, suggesting that holoTf endocytosis could be important for the parasite during colonization and invasion of the intestinal mucosa and liver.


2000 ◽  
Vol 350 (3) ◽  
pp. 909-915 ◽  
Author(s):  
Qing-Yu HE ◽  
Anne B. MASON ◽  
Vinh NGUYEN ◽  
Ross T. A. MacGILLIVRAY ◽  
Robert C. WOODWORTH

The major function of human transferrin is to deliver iron from the bloodstream to actively dividing cells. Upon iron release, the protein changes its conformation from ‘closed’ to ‘open’. Extensive studies in vitro indicate that iron release from transferrin is very complex and involves many factors, including pH, the chelator used, an anion effect, temperature, receptor binding and intra-lobe interactions. Our earlier work [He, Mason and Woodworth (1997) Biochem. J. 328, 439–445] using the isolated transferrin N-lobe (recombinant N-lobe of human transferrin comprising residues 1–337; hTF/2N) has shown that anions and pH modulate iron release from hTF/2N in an interdependent manner: chloride retards iron release at neutral pH, but accelerates the reaction at acidic pH. The present study supports this idea and further details the nature of the dual effect of chloride: the anion effect on iron release is closely related to the strength of anion binding to the apoprotein. The negative effect seems to originate from competition between chloride and the chelator for an anion-binding site(s) near the metal centre. With decreasing pH, the strength of anion binding to hTF/2N increases linearly, decreasing the contribution of competition with the chelator. In the meantime, the ‘open’ or ‘loose’ conformation of hTF/2N, induced by the protonation of critical residues such as the Lys-206/Lys-296 pair at low pH, enables chloride to enter the cleft and bind to exposed side chains, thereby promoting cleft opening and synergistically allowing removal of iron by the chelator, leading to a positive anion effect. Disabling one or more of the primary anion-binding residues, namely Arg-124, Lys-206 and Lys-296, substantially decreases the anion-binding ability of the resulting mutant proteins. In these cases, the competition for the remaining binding residue(s) is increased, leading to a negative chloride effect or, at most, a very small positive effect, even at low pH.


Diabetes ◽  
1985 ◽  
Vol 34 (5) ◽  
pp. 462-470 ◽  
Author(s):  
K. A. Ney ◽  
J. J. Pasqua ◽  
K. J. Colley ◽  
C. E. Guthrow ◽  
S. V. Pizzo
Keyword(s):  

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