Serum transferrins

Harris WR (1998) Binding and Transport of Nonferrous Metals by Serum Transferrin. 92 121-162... 

Kilar, E and Hjerten,S., Fast and high resolution analysis of human serum transferrin by high performance isoelectric focusing in capillaries, Electrophoresis, 10, 23, 1989. 

Kilar, F. and Fanali, S., Separation of tryptophan-derivative enantiomers with iron-free human serum transferrin by capillary zone electrophoresis, Electrophoresis, 16, 1510, 1995. 

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,... 

A recently obtained high resolution structure of two crystal forms of the N-lobe of human serum transferrin (at 0.16 and 0.18 nm resolution) shows disorder at the iron-binding sites (MacGillivray et ah, 1998). Model building and refinement show... 

FIGURE 5.8 Complex hyperfine patterns due to axes noncolinearity in a low-symmetry prosthetic group. The X-band spectrum is from 65Cu(II)-bicarbonate in human serum transferrin (a,b) experimental spectrum (c,e) simulation assuming axial symmetry (d, f) simulation assuming triclinic symmetry with the A-axes rotated with respect to the g-axes over 15° about the gz-axis and then 60° about the new y -axis. Traces b, e, and f are 5x blow-ups of traces a, c, d, respectively (Hagen 2006). (Reproduced by permisson of The Royal Society of Chemistry.)... 

Schewale, J.G., and Brew, K. (1982) Effects of Fe3+ binding on the microenvironments of individual amino groups in human serum transferrin as determined by different kinetic labeling. /. Biol. Chem. 257, 9406. 

Mason, A.B., Halbrooks, P.J., James, N.G., Connolly, S.A., Larouche, J.R., Smith, V.C., MacGillivray, R.T.A. and Chasteen, N.D. (2005) Mutational analysis of C-lobe ligands of human serum Transferrin insights into the mechanism of iron release, Biochemistry, 44, 8013-8021. 

An interesting application of CZE was the study of the interaction of human serum transferrin and fluorescein isothiocyanate (FITC). Measurements were carried out in an uncoated fused-silica capillary (total length 59 cm 75 pm i.d. effective lengths for... 

T. Konecsni and F. Kilar, Monitoring of the conjugation reaction between human serum transferrin and fluorescein isothiocyanate by capillary electrophoresis. J. ChromatogrA, 1051 (2004) 135-139. 

Alcohol consumption is very difficult to assess. There is widespread belief that individuals underreport their intake and there are no reliable laboratory tests available for definitive diagnosis of alcohol abuse. A combination of abnormalities in the plasma activity of gamma-glutamyl transferase (GGT or yGT), AST and reduction in erythrocyte mean cell volume (MCV) maybe useful and all are routine lab. tests. A potential marker of interest is carbohydrate-deficient transferrin (CDT) which is an abnormal isoform of serum transferrin arising due to defects in the attachment of carbohydrate chains to the protein core. Unfortunately, CDT is a somewhat specialized test, not performed by most laboratories. Other markers which have attracted some research interest are ethyl sulphate and ethyl glucuronide. Excretion in the urine of these metabolites occurs for up to 50 hours after binge drinking so they offer a useful index of recent heavy alcohol intake. 

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]. 

F Kilar, S Hjerten. Unfolding of human serum transferrin in urea studied by high-performance capillary electrophoresis. J. Chromatogr. 638 269-276... 

F Kilar. Stereoselective interaction of drug enantiomers with human serum transferrin in capillary zone electrophoresis. Electrophoresis 17 1950-1953, 1996. 

CDT is the collective name of a gronp of minor isoforms of serum transferrin [14] with a low degree of glycosylation, inclnding asialo-, monosialo-, and disialo-Tf. CDT concentrations in serum are elevated during prolonged alcohol overconsnmption (>50-80 g/day for at least 7 days) and decrease, after... 

Detailed pictures of the iron-binding sites in transferrins have been provided by the crystal structures of lactoferrin (Anderson et ai, 1987, 1989 Baker etai, 1987) and serum transferrin (Bailey etal., 1988). Each structure is organized into two lobes of similar structure (the amino- and carboxy-terminal lobes) that exhibit internal sequence homology. Each lobe, in turn, is organized into two domains separated by a cleft (Fig. 3 and 10). The domains have similar folding patterns of the a//3 type. One iron site is present in each lobe, which occupies equivalent positions in the interdomain cleft. The same sets of residues serve as iron ligands to the two sites two tyrosines, one histidine, and one aspartate. Additional extra density completes the octahedral coordination of the iron and presumably corresponds to an anion and/or bound water. The iron sites are buried about 10 A below the protein surface and are inaccessible to solvent. 

The molecular details of the physiologically critical step of iron release from serum transferrin are unclear. The anion may play an important role in this process by providing a handle for modulating the affinity of transferrin for iron. If the anion were to be removed (perhaps by protonation followed by dissociation), then the binding of iron to transferrin would be greatly weakened, facilitating dissociation of the metal. It seems... 

Ser Se isotopic substitution, 38 105-107 Serum albumin, 46 470 Serum transferrins, 41 390 biological role, 41 391-392 half-molecules, 41 396 recombinant, 41 453 structure, 41 397... 

Fig. 11a and b. Oscillation patterns recorded from a 6-phosphogluconate dehydrogenase and b rabbit serum transferrin showing rich and highly oriented molecular diffuse scattering features... 

Mechanism of Action An enzymatic mineral that is an essential component in the formation of Hgb, myoglobin, and enzymes. Promotes effective erythropoiesis and transport and utilization of oxygen (Oj). Therapeutic Effect Prevents iron deficiency. Pharmacokinetics Absorbed in the duodenum and upper jejunum. Ten percent absorbed in patients with normal iron stores increased to 20%-30%in those with inadequate iron stores. Primarily bound to serum transferrin. Excreted in urine, sweat, and sloughing of intestinal mucosa. Half-life 6 hr. 

Increased erythropoiesis is associated with an increase in the number of transferrin receptors on developing erythroid cells. Iron store depletion and iron deficiency anemia are associated with an increased concentration of serum transferrin. 

Serum transferrin is the transport protein of ferric iron ions in mammalians. 

A novel approach in initial CDG diagnostics has currently been described by analysing the glycosylation state of serum transferrin using electrospray ionisation-tandem mass spectrometry (ESI-MS/MS). This method requires expensive technical... 

Fig. 4.5.2 Actual strategies for CDG diagnosis. Initial investigations on CDG patients are routinely carried out by isoelectric focusing (IEF) of serum transferrin. With a CDG type I pattern, subsequent analysis should imply determination of phosphomannomutase (PMM) and phos-phomannose isomerase (PMI) activities. Further studies, like analysis of the lipid-linked- and protein-bound-oligosaccharides, determination of enzyme or sugar transporter activities and molecular biology studies often have to be performed in more specialised laboratories. HPLC High-performance liquid chromatography, TLC thin-layer chromatography...

Although IEF of serum transferrin is relatively easy to perform, it is assumed that many CDG patients are still missed. Due to the complex clinical presentation of CDG, all patients suffering from unclear multi-organ diseases, especially in combination with mental and psychomotor retardation, strabismus, cerebellar atrophy and blood-clotting problems, should be investigated for CDG. 

In all known types of CDG-I it has been observed that due to the loss of sialic acid residues, in addition to tetrasialo-transferrin, more or less pronounced di- and asialo-transferrin bands appear, which are evoked by the loss of either one or both complete oligosaccharide chains (Fig. 4.5.3, lanes 2-4). In contrast to CDG-I, changes in the charge of serum transferrin of most known CDG-II types are due to shortening of the oligosaccharide moieties (Fig. 4.5.3, lanes 5-7). 

Fig. 4.5.3 IEF patterns of serum transferrin. Sera from a control (lane 1), three CDG-I (CDG-Ia, CDG-Ic and CDG-Id lanes 2-4) and three CDG-II patients (CDG- , CDG-IId and CDG-IIx lanes 5-7) were analysed by IEF. In case of a control person, the main form of the protein carries four negatively charged sialic acid residues, even though small amounts of penta- and trisialo-transferrin are detectable. Additional disialo- and asialotransferrin forms indicate CDG-type I (left side). In some cases of CDG type II, additional trisialo- and monosialotransferrin forms may occur, which are due to the loss of either one or three sialic acid residues (right side). Isoforms of transferrin that are independent of a pathological phenotype and that cause double bands in IEF are visible in lanes 4 and 6. CDG-IIx indicates a transferrin pattern that is caused by a so far unknown molecular defect from the CDG-II type...

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