A 150-kDa transferrin-like protein (Ttf) is associated with the plasma membrane of the halotolerant unicellular alga Dunaliella salina (Fisher, M., Gokhman, I., Pick, U., and Zamir, A. (1997) J. Biol. Chem. 272, 1565-1570). The Ttf level rises with medium salinity or upon iron depletion. Evidence that Ttf is involved in iron uptake by Dunaliella is presented here. Algal iron uptake exhibits cha...

The sugar chains of transferrin samples, purified from sera of patients with hepatocellular carcinoma and of healthy individuals, were released quantitatively as radioactive oligosaccharides by hydrazinolysis followed by N-acetylation and NaB3H4 reduction. Comparative study of their structure by serial lectin column chromatography, by Bio-Gel P-4 column chromatography, and by sequential exoglyc...

Human transferrin receptor is a disulfide-linked homodimer of 90-kDa glycoprotein subunits, capable of binding two transferrins. We report a new high yield affinity purification protocol for transferrin receptor from placenta which produces 3-4 mg of highly purified protein. Trypsin cleaves the protein at arginine-121, producing a stable fragment that contains 95% of the extracytoplasmic sequen...

A rapid and sensitive technique, involving difference spectral titration with cobalt(III), to measure the epsilon values of chicken ovotransferrin, human serum transferrin, the N-lobe of human transferrin and several single point mutants is reported. The resulting epsilon values were compared with the values calculated from the equation proposed by Pace, Vajdos, Fee, Grimsley and Gray [(1995) P...

Transferrins belong to a family of iron-binding proteins that have been implicated in innate immunity and in vitellogenesis in insects. Here we have sequenced and characterized a full-length cDNA encoding a putative iron-binding transferrin (AmTRF) in the honeybee. AmTRF shows high level of sequence identity with transferrins in both vertebrates and insects (26-46%) suggesting that the primary ...

The denaturation of transferrin by urea has been studied by (a) electrophoresis in polyacrylamide gels incorporating a urea gradient, (b) measurements of the loss of iron-binding capacity and (c) u.v. difference spectrometry. In human serum transferrin and hen ovotransferrin the N-terminal and C-terminal domains of the iron-free protein were found to denature at different urea concentrations.

tebrates by their abi}ity to bind tvvo Fe3' and two CO;-. The transfenin molecule, with a mo]ecu)ar mass of about 80 kDa, is folded into two similarly sized homologous Nand C-lobes that are stabilized by many intrachain disulfides. As observed by X-ray crystallography, each lobe is further diyided into two similarly sized domains, domain 1 and domain 2, and an Fe3+binding site is within the int...

Transferrin receptor 1 (R) and human serum transferrin (T) are the two main actors in iron acquisition by the cell. R binds TFe(2) (iron-loaded transferrin), which allows its internalization in the cytoplasm by endocytosis. T also forms complexes with metals other than iron. In order to follow the iron-acquisition pathway, these metals should obey at least two essential rules: (i) formation of ...