[Preparation and partial physico-chemical characterization of sheep-serum transferrin]

An unusual transferrin variant in sheep

An unusual variant, Tf Aw, has been found in sheep transferrins. It position in starch gel electrophoresis is identical with the variant Tf A, but the intensity of corresponding bands is substantially lower. Family analyses prove that the variant Aw is genetically controlled and represents either the product of an unusual allele Tf Aw or the interaction between the allele Tf A and a hypothetical modifying locus.

Heterogeneity of horse transferrin: the role of carbohydrate moiety

Homozygous horse transferrin (Tf O) is highly heterogeneous. In starch gel electrophoresis it gives at least 9 zones. Two main components (2a and 4b) were purified by rivanol and ammonium sulphate precipitation, DEAE-Sephadex chromatography and SP-Sephadex chromatography. Molecular weights of 75 200 and 80 500 for components 2a and 4b, respectively, were determined by sedimentation equilibrium ultracentrifugation. Amino acid compositions of the two components were similar, and there were no differences in the N-terminus (glutamic acid followed by glutamine) and the C-terminus (valine). Differences were found in carbohydrate composition between components 2a and 4b. Component 2a contained 10 moles of sugar components per mole of protein (4 hexoses, 4 hexosamines and 2 sialic acids), while component 4b contained twice the number of both total carbohydrates and individual sugar components. Carbohydrates were identified as mannose and galactose (ratio mannose: galactose approximately equal to 1.5:1), N-acetylglucosamine and N-acetylneuraminic acid. At present it is not clear whether the difference between the two components resides solely in the difference of carbohydrate contents. It is proposed that component 2a has one diantennary glycan, while component 4b has two.

Effect of Lactoferrin on the Ferroxidase Activity of Ceruloplasmin

The effects of various forms of lactoferrin (Lf) interacting with ceruloplasmin (Cp, ferro-O2-oxidoreductase, EC 1.16.3.1) on oxidase activity of the latter were studied. Comparing the incorporation of Fe3+ oxidized by Cp into Lf and serum transferrin (Tf) showed that at pH 5.5 apo-Lf binds the oxidized iron seven times and at pH 7.4 four times faster than apo-Tf under the same conditions. Apo-Lf increased the oxidation rate of Fe2+ by Cp 1.25 times when Cp/Lf ratio was 1 : 1. Lf saturated with Fe3+ or Cu2+ increased the oxidation rate of iron 1.6 and 2 times when Cp to holo-Lf ratios were 1 : 1 and 1 : 2, respectively. Upon adding to Cp the excess amounts of apo-Lf (Cp/apo-Lf < 1 : 1) or of holo-Lf (Cp/holo-Lf < 1 : 2) the oxidation rate of iron no longer changed. Complex Cp-Lf demonstrating ferroxidase activity was discovered in breast milk.

Comparative study of the primary structures of sero-, lacto- and ovotransferrin glycans from different species

In order to establish relationships between glycan structure and biological activity and to answer the question: Are glycans markers of evolution?, the authors undertook a comparative study of the glycan primary structures of different transferrins (sero-, lacto- and ovotransferrins) from several species. By associating permethylation--mass spectrometry and 1H NMR spectroscopy, the primary structure of the following transferrin glycans were determined: human, bovine, hen, horse, marsupial, mouse, rabbit, rat and sheep serotransferrins; human, mouse, bovine and goat lactotransferrins; hen and turkey ovotransferrins. The results obtained led to the conclusion that transferrin glycans are specific for each transferrin and, for a given transferrin, specific to the species. No relationship could be established a priori between primary structure and function of transferrin glycans.

Some association properties of bovine SH-kappa-casein

(1) It is shown that kappa-casein association is characterized by a critical micelle concentration which decreases as the ionic strength is increased. (2) The kappa-casein polymer molecular weight was calculated from the weight-average apparent molecular weight by taking into consideration the monomer concentration and the excluded volume. The degree of polymerization is 30 and does not depend on ionic strength between 0.1 and 1 M. (3) The non-electrical contribution to the standard free energy of association is -38 kJ/mol monomer. The electrical part is small: 1-2 kJ/mol monomer depending on the ionic strength and kappa-casein genetic variant. (4) The limitation of size and the size itself of the kappa-casein polymer can be explained by the theory of self-assembly of virus particles by Caspar and Klug (D.L.D. Caspar and A. Klug, Cold Spring Harb. Symp. Quant. Biol. 27 (1962)1). (5) Extending this theory to casein micelle assembly, it is predicted that micelles are distributed preferentially over a restricted number of sizes.

Electrophoretic mobility of N- and C-terminal monoferric fragments of bovine transferrin phenotypes AA, D1D1, D2D2, and EE, and N-terminal amino acid sequences

Iron-saturated bovine transferrins A, D1, D2 and E were cleaved by trypsin yielding monoferric fragments. The N-terminal fragments (F) of transferrins A and D2 had identical mobility in cellulose acetate electrophoresis, that of transferrin D1 a slower mobility, and that of E a still slower mobility. The C-terminal fragments (S) gave multiple bands which were essentially identical in the case of transferrins A, D1, and E, but of slower mobility in the case of transferrin D2. All four variants had identical N-terminal amino acid sequences. The electrophoretic mobility of the C-terminal fragments was reduced by neuraminidase treatment, but the N-terminal fragments were unaffected. The four transferrin variants therefore appear to be made up from three electrophoretically distinguishable N-terminal halves and two C-terminal halves. The feature responsible for the electrophoretic double banding of homozygous bovine asialotransferrins is consistently associated with the C-terminal half of the molecule.

Molar absorptivity and A1%1 cm values for proteins at selected wavelengths of the ultraviolet and visible regions--XVIII

A table of molar absorptivity and A1cm1% values for more than 180 proteins is given. The conditions used to obtain these values and references to the original literature are also'given.

Demonstration of the simultaneous presence of transferrin, hemopexin and albumin in the same adult rat hepatocyte

The location of three plasma proteins (transferrin, hemopexin, and albumin) in hepatocytes was investigated in adult rats. The synthesis of transferrin anf hemopexin has been established by ultrastructural studies showing a labeling of the rough endoplasmic reticulum (RER). By using an indirect immunoenzymatic method with monospecific antibody solutions, the three proteins were detected in the same hepatocyte. The simultaneous presence of different plasma proteins in hepatocytes seems to point to the fact that the synthesis in these cells could be a non-specialized type.