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Query: UNIPROT:P02794 (ferritin)
 17,525 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The interactions of horse spleen ferritin and its derivative apoferritin with H+ ions were studied by potentiometric and spectrophotometric titration; to aid in data analysis, heats of ionization over a limited pH range and amide content were also determined. Per apoferritin subunit, all tyrosine and cysteine side chains, two of the nine lysine side chains and at least three of the six histidine side chains were found not to titrate; a preliminary but self-consistent analysis of the titration data is proposed. The titration curve of ferritin was identical with that of apoferritin in the pH range 5.5 to 3. In addition, under the conditions used, the reactivities of ferritin histidines to bromoacetate and of ferritin lysines to formaldehyde were identical with those in apoferritin. Above pH 8, a time-dependent titration of the ferritin core occurs which prevents comparison of the titration curves of the two proteins in this region. However, in the pH regions 5.5 to 7.5, two extra groups per subunit titrate reversibly in ferritin relative to apoferritin. Moreover, although the isoionic points of ferritin and apoferritin are identical in water, the isoionic point of ferritin is 0.5 pH unit lower than that of apoferritin in 0.16 to 1 M KCl. The different effects of KCl and NaCl on the two proteins indicate the presence of cation binding sites in ferritin that are absent in apoferritin and possibly also the presence of anion binding sites in apoferritin that are occupied in ferritin by anions of the core. The difference between the isoionic points of the two proteins in KCl has been interpreted to indicate the presence of approximately 2 phosphate residues per ferritin subunit which serve as cation binding sites and which are negatively charged at the isoionic point in KCl. These phosphates may also represent the additional residues that titrate in ferritin between pH 5.5 and 7.5, or may interact with positively charged residues on the inner surface of the ferritin shell, or both.
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PMID:Hydrogen ion interactions of horse spleen ferritin and apoferritin. 1 Dec 12

The effect of chromium on some parameters related to iron metabolism was investigated. Preliminary experiments showed that this metal ion was taken up by serum proteins and was dependent on the amount of chromium present in the medium. It was also shown that the uptake of iron was reduced significantly in the presence of chromium. In vivo study showed that the serum levels of iron and total iron binding capacity (TIBC) were reduced by 28 and 11%, respectively, following daily administration of chromium (1 mg/kg) for 45 d. Serum ferritin was reduced by 22% under this condition. Hematocrit and hemoglobin levels were also affected in chromium-treated animals and were both reduced by 17%. Spectrophotometric titration of each individual amino acid located in the iron binding site of transferrin revealed that tyrosine might be the most suitable ligand for the binding of chromium to transferrin. These results suggest that chromium may compete with iron in binding to apo-transferrin, and influence iron metabolism and its related biochemical parameters.
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PMID:The effect of chromium on parameters related to iron metabolism. 137 87

A comparative study of rabbit IgG, both native and modified ones, designed to assess the functional activity of these proteins under oxidative iodination conditions has been carried out. Polyclonal IgG, its antigen-specific fraction and Iodogen as an oxidant were used. Polyclonal antibodies directed against the CH2 domain of IgG, protein A targeted at the CH-2-CH3 domain interface and ferritin testing the conformation of the antigen-binding Fv fragment, were applied as conformational probes for assessing the changes in the IgG conformation. By taking advantage of pepsin proteolysis of [125I]-IgG, from 80% to 92% of the label was found to be localized within the CH3 domain, thus implying the domain-selective nature of iodination, when the degree of modification was below 0.1 atom of iodine per IgG molecule. Yet, when the three above-mentioned conformational probes were used, considerable alterations in the conformation of not only the CH2 domain and CH2-CH3 domain interface, but in the Fv domain being a part of the Fab fragment, were observed. By using competitive enzyme immunoassay for the straightforward comparative evaluation of functional properties of "cold" (native) and 125I-modified IgG, the deleterious effect of the oxidant (Iodogen) rather than iodine atom substitution at the phenolic ring of Tyr residues was shown to be the major determinant of alterations in the IgG molecule.
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PMID:[Oxidative iodination of rabbit IgG: localization of markers in an Fc-fragment and effects of modification]. 174 12

Treatment for phenylketonuria (PKU) involves using low phenylalanine-free or phenylalanine-free formulas and supplementation with sufficient phenylalanine for normal growth and development. Eighteen infants with phenylketonuria who received breast milk as their primary phenylalanine source were compared with ten other infants with PKU who received their phenylalanine primarily from infant formulas. There were no significant differences between breast-fed and formula-fed infants for serum phenylalanine, serum tyrosine, length, weight, head circumference, haematocrit, haemoglobin, serum iron, total iron binding capacity, percentage iron saturation, ferritin, plasma zinc and total calorie intake. Breast-fed infants did show lower mean corpuscular volume at 3 months and 6 months of age. Breast-fed infants had lower phenylalanine intake at 2, 4, 5 and 6 months of age. Breast-fed infants at 1, 2, 3, 4, 5 and 6 months of age had lower protein intake. Breast feeding may be continued in the newly diagnosed phenylketonuric infant without any apparent adverse nutritional consequences.
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PMID:The management of breast feeding among infants with phenylketonuria. 251 78

The occurrence of an oxo-bridged binuclear iron site is well-established for the oxygen transport protein, hemerythrin, and strongly implicated in ribonucleotide reductase, purple acid phosphatase, ferritin, and methane monooxygenase. Key identifying characteristics are an antiferromagnetic interaction between the two iron atoms, an Fe-O-Fe vibrational mode in the resonance Raman spectrum, and an S = 1/2 EPR signal upon one-electron reduction. In hemerythrin the oxo bridge serves as a hydrogen bond acceptor which stabilizes the bound hydroperoxide. In ribonucleotide reductase both the binuclear iron center and a protein tyrosine undergo oxidation in the presence of molecular oxygen, whereas in methane monooxygenase a binuclear iron moiety may activate O2 for substrate oxygenation.
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PMID:Involvement of oxo-bridged binuclear iron centers in oxygen transport, oxygen reduction, and oxygenation. 304 60

The number of gene assignments to human chromosome 20 has increased slowly until recently. Only seven genes and one fragile site were confirmed assignments to chromosome 20 at the Ninth Human Gene Mapping Workshop in September 1987 (HGM9). One fragile site, 13 additional genes, and 10 DNA sequences that identify restriction fragment length polymorphisms (RFLPs), however, were provisionally added to the map at HGM9. Five mutated genes on chromosome 20 have a relation to disease: a mutation in the adenosine deaminase gene results in a deficiency of the enzyme and severe combined immune deficiency; mutations in the gene for the growth hormone releasing factor result in some forms of dwarfism; mutations in the closely linked genes for the hormones arginine vasopressin and oxytocin and their neurophysins are probably responsible for some diabetes insipidus; and mutations in the gene that regulates both alpha-neuraminidase and beta-galactosidase activities determine galactosialidosis. The gene for the prion protein is on chromosome 20; it is related to the infectious agent of kuru, Creutzfeld-Jacob disease, and Gertsmann-Straussler syndrome, although the nature of the relationship is not completely understood. Two genes that code for tyrosine kinases are on the chromosome, SRC1 the proto-oncogene and a gene (HCK) coding for haemopoietic kinase (an src-like kinase), but no direct relation to cancer has been shown for either of these kinases. The significance of non-random loss of chromosome 20 in the malignant diseases non-lymphocytic leukaemia and polycythaemia vera is not understood. Twenty-four additional loci are assigned to the chromosome: five genes that code for binding proteins, one for a light chain of ferritin, genes for three enzymes (inosine triphosphatase, s-adenosylhomocysteine hydrolase, and sterol delta 24-reductase), one for each of a secretory protein and an opiate neuropeptide, a cell surface antigen, two fragile sites, and 10 DNA sequences (one satellite and nine unique) that detect RFLPs.
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PMID:The map of chromosome 20. 307 44

Nine cases of childhood malignant histiocytosis (MH) showed an abnormally high serum phenylalanine (Phe)/tyrosine (Tyr) ratio (3.47 +/- 1.32) coincident with hyperferritinemia (50,800 +/- 33,600 ng/ml). Lactate dehydrogenase activity was also increased in these patients. These values were compared with data on sera from two groups of patients, acute leukemia cases (n = 14) and measles cases (n = 13), and with control values from normal healthy children (n = 38). The Phe/Tyr ratio was 1.57 +/- 0.54 for the acute leukemia (p less than 0.01) and 2.58 +/- 1.46 for the measles cases (NS), serum ferritin was 245 +/- 124 ng/ml for acute leukemia (p less than 0.01) and 167 +/- 117 ng/ml for measles (p less than 0.01). Accordingly, the concurrence of both abnormalities is considered to be characteristic for MH. It was also found that both serum Phe/Tyr ratio and ferritin levels reflect the disease activity, indicating that these two factors are useful prognostic indicators in the treatment of patients with MH.
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PMID:Abnormal serum phenylalanine-tyrosine ratio and hyperferritinemia in malignant histiocytosis. 315 76

1. The dissociation of horse spleen apoferritin as a function of pH was analysed by sedimentation-velocity techniques. The oligomer is stable in the range pH2.8-10.6. Between pH2.8 and 1.6 and 10.6 and 13.0 both oligomer and subunits can be detected. At pH values between 1.6 and 1.0 the subunit is the only species observed, although below pH1.0 aggregation of the subunits to a particle sedimenting much faster than the oligomer occurs. 2. When apoferritin is first dissociated into subunits at low pH values and then dialysed into buffers of pH1.5-5.0, the subunit reassociates to oligomer in the pH range 3.1-4.3. 3. U.v.-difference spectroscopy was used to study conformational changes occurring during the dissociation process. The difference spectrum in acid can be accounted for by the transfer of four to five tyrosine residues/subunit from the interior of the protein into the solvent. This process is reversed on reassociation, but shows the same hysteresis as found by sedimentation techniques. The difference spectrum in alkali is more complex, but is consistent with the deprotonation of tyrosine residues, which appear to have rather high pK values. 4. In addition to the involvement of tyrosine residues in the conformational change at low pH values, spectral evidence is presented that one tryptophan residue/subunit also changes its environment before dissociation and subsequent to reassociation. 5. Analysis of the dissociation and reassociation of apoferritin at low pH values suggests that this is a co-operative process involving protonation and deprotonation of at least two carboxyl functions of rather low intrinsic pK. The dissociation at alkaline pH values does not appear to be co-operative. 6. Of the five tyrosine residues/subunit only one can be nitrated with tetranitromethane. Guanidination of lysine residues results in the modification of seven out of a total of nine residues/subunit. Nine out of the ten arginine residues/subunit react with cyclohexanedione.
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PMID:Subunit interactions in horse spleen apoferritin. Dissociation by extremes of pH. 473 25

1. Horse spleen apoferritin catalyses the oxidation of Fe(2+) to Fe(3+) with molecular O(2) as electron acceptor under conditions where a number of other proteins have no such effect. The product is similar to ferritin by a number of criteria. 2. The progress curve is hyperbolic and the increase in initial velocity is linear with increasing apoferritin concentration. With respect to Fe(2+) the reaction follows Michaelis-Menten kinetics. The pH-dependence of the reaction was determined between pH4.3 and 6.0. 3. Modification of both tryptophan residues/apoferritin subunit with 2-nitrophenylsulphenyl chloride does not affect either k(cat.) or K(m) for the oxidation. Neither does the guanidination of seven out of nine lysine residues/subunit, the modification of nine out of ten arginine residues/subunit with cyclohexanedione, or the nitration of one out of five tyrosine residues/subunit with tetranitromethane. 4. The carboxymethylation of two out of three cysteine residues/subunit and of one out of six histidine residues/subunit can be achieved with iodoacetic acid. This carboxymethylated apoferritin is completely inactive in Fe(2+) oxidation. 5. Apoferritin does not take up Fe(3+). It appears from these results that Fe(2+) is the form in which iron is taken up by ferritin in a reaction where the protein acts as an enzyme which traps the product in the interior of the protein shell.
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PMID:The catalytic activity of horse spleen apoferritin. Preliminary kinetic studies and the effect of chemical modification. 473 26

Structural, spectroscopic, and immunological properties of horse ferritins extracted from spleen, liver, and heart were studied to test the hypothesis that the different tissue ferritins are hybrids composed of variable proportions of two subunit types. The weight-average molecular weights determined by sedimentation velocity and gel filtration increase from 460 000 for spleen to 480 000 for liver and to 515 000 for heart apoferritin; moreover, the diffusion coefficients prove that each tissue-specific ferritin consists of a population of hybrid molecules. The intrinsic fluorescence and the near-UV circular dichroism (CD) spectra change as a function of the subunit composition of the three ferritins. The fluorescence emission maximum, which occurs at a very low wavelength (315 nm) in horse spleen apoferritin, is shifted to increasingly higher wavelengths in the liver and heart proteins (320 and 325 nm, respectively), indicating that the tryptophan and tyrosine residues become less rigidly immobilized with an increase in the H-subunit content. The tryptophan residues behave as fully solvated in the monomeric subunits at acidic pH values. In accordance with the fluorescence data, the near-UV CD spectra show that the tryptophan environment is highly asymmetric in spleen apoferritin, progressively less so in liver and heart apoferritins, and completely relaxed in the dissociated subunits. Moreover, they show that the environment of tyrosines and phenylalanines differs markedly in the spleen and heart apoproteins. The ferritins studied appear to have immunogenic sites which are specific for the H and L subunits on the basis of enzyme-linked immunoassay and double-diffusion experiments.
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PMID:Structural heterogeneity and subunit composition of horse ferritins. 709 88


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