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At least 19 recordsLinked to original sources
PubMed1975

Studies on thyroid hormone-binding proteins. II. Binding of thyroid hormones, retinol-binding protein, and fluorescent probes to prealbumin and effects of thyroxine on prealbumin subunit self association.

Vitamin A in human plasma is transported by its specific carrier protein, the retinol-binding protein. Under physiological conditions the protein forms a stable protein-protein complex with the tetrameric plasma protein, the thyroxine-binding prealbumin. Human prealbumin was shown to interact with the fluorescent probes 1,8-anilinonaphthalene sulfonate (ANS) and 2-p-toluidinylnaphthalene-6-sulfonate (TNS). ANS bound to the protein at two independent sites with the apparent association constant 3 X 10(5) M-1, whereas TNS interacted with a single site with the binding constant 5 X 10(k) M-1. The fluorescent yield of protein-bound ANS was 0.95, a more than 200-fold enhancement compared with that of ANS in aqueous solutions. TNS enhanced its quantum yield nearly 500-fold to 0.37. On addition of thyroid hormones the fluorescent probes could be quantitatively displaced from the protein. This finding suggested that triiodthyronine, thyroxine, and the probes bound to a common site in prealbumin, which is likely to have a strongly hydrophobic character. The association constants for the interaction between prealbumin and the thyroid hormones could be calculated by using the hormones as competitive inhibitors in the TNS-prealbumin titrations. The data from the competition experiments together with those obtained from equilibrium dialysis revealed one major hormone binding site on the protein. The calculated association constant were 9 X 10(6) M-1 and 1 X 10(8) M-1 for triiodothyronine and thyroxine, respectively. Prealbumin monomers were bound to Sepharose by covalent attachment, and their properties were examined. Evidence was obtained demonstrating that the retinol-binding protein could interact with a single subunit of prealbumin. The estimated apparent association constant for the interaction of the protein and the matrix-bound monomeric prealbumin was 3 X 10(4) M-1, approximately 250-fold lower than that measured for protein and matrix-bound tetrameric prealbumin. The data, however, strongly suggest that there are four retinol-binding protein sites per prealbumin molecule. Using the technique of sedimentation equilibrium ultracentrifugation the prealbumin subunit self-association has been studied. The energy of the interaction for the prealbumin subunits is very high, and various concentrations of guanidine hydrochloride has to be used to perturb the equilibrium. All experiments indicated that prealbumin dissociates directly into monomers without the presence of intermediate forms. Thyroxine perturbed the chemical equilibrium of the prealbumin monomer-tetramer system by strengthening the interaction between the subunits.

Anilino Naphthalenesulfonates↗
PubMed1976

The interaction between retinol-binding proteins and prealbumins studied by fluorescence polarization.

The interaction between retinol-binding proteins and prealbumins of human and chicken was studied by fluorescence polarization techniques. The binding affinity between chicken plasma retinol-binding protein and chicken prealbumin was essentially the same as between the respective human proteins. Human urine retinol-binding protein displayed a similar affinity, though possibly slightly smaller than that of the human plasma protein, toward human prealbumin. Retinol-binding proteins and prealbumins of human and chicken have been found to cross-interact displaying an affinity similar to that displayed by the proteins of the same species. Solution of a binding equation which assumes identical, independent sites, indicated that the number of binding sites on prealbumin for retinol-binding protein is somewhat less than 2 with the human system, and in the neighborhood of 4 with the chicken system. A possible interpretation suggests that prealbumin possesses four identical binding sites for retinol-binding protein, one for each subunit, but that the binding is of a negative cooperative nature. A major share of the negative cooperativity is likely to result from steric hindrance induced by already bound retinol-binding protein molecules, which have a sizable volume compared to the volume of the prealbumin molecule. The cooperativity is likely to be more pronounced with the human system. Rotational relaxation times derived from Perrin plots suggest that 1:1 molecular complexes of retinol-binding proteins with prealbumins have a compact structure.

Animals↗
PubMed1977

Purification of a bovine counterpart to human prealbumin and its interaction with a bovine retinol-binding protein.

A bovine counterpart to human prealbumin was purified from bovine serum by thiol-disulfide exchange chromatography on thiol-Sepharose 4B and affinity chromatography on human retinol-binding protein linked to Sepharose 4B. The bovine prealbumin had alpha1-mobility on agarose gel electrophoresis at pH 8.6. It has the same molecular weight as human prealbumin on gel filtration and consisted of subunits with a molecular weight of 12 500. This is compatible with a tetrameric structure for the bovine protein. Antiserum against human prealbumin cross-reacted with bovine prealbumin and vice versa. The bovine prealbumin formed at high ionic strength complexes with another bovine serum protein which were dissociated at low ionic strength. This property was used to isolate a protein from bovine serum, by chromatography on bovine prealbumin linked to Sepharose which cross-reacted with antiserum against human retinol-binding protein; had a molecular weight of 21 000 and alpha 2-mobility on agarose gel electrophoresis. It was concluded that the latter protein was a bovine retinol-binding protein.

Animals↗
PubMed1978

Thymic hormone-like restoration by human prealbumin of azathioprine sensitivity of spleen cells from thymectomized mice.

Gel filtration of fresh human serum revealed that over 95% of the thymic-hormone-like activity was present in the fraction representing the total albumin and prealbumin. Further studies demonstrated that the activity resided in the prealbumin fraction; albumin was inactive. Prealbumin was isolated from Cohn fraction IV-1 of pooled human plasma by extraction with aqueous buffer, fractionation with (NH4)2SO4, gel filtration on Sephadex G-150, and preparative disc gel electrophoresis. The final product was homogeneous by analytical gel electrophoresis was 40,000 times more active than the starting material in an azathioprine-sensitive rosette assay. Physical and chemical characterization studies showed that the isolated product was identical to authentic human plasma prealbumin. Isolation of the prealbumin fraction from sera of adult thymectomized mice revealed that the rosette activity was substantially lower than that isolated from sera of normal mice, suggesting a thymic dependence of the prealbumin activity. In vitro and in vivo bioassays of the fraction obtained prior to the final step of the purification procedure support the conclusion that prealbumin exhibits thymic hormone-like activity.

Animals↗
PubMed1979

Prealbumin as a hapten carrier protein in certain varieties of dermatitis.

A significant decrease of serum prealbumin levels and an increased proportion of prealbumin bearing lymphocytes in peripheral blood have been found in patients of hapten-induced diseases. Prealbumin deposition in the vessel walls, and/or prealbumin positive cells (granulocytes, lymphocytes, macrophages) in the dermis have been observed in patients with proved drug allergy as well as allergic contact dermatitis using immunofluorescence technique. The eluates from membrane of lymphocytes of patients with drug allergy contained a mitogenic substance, probably antigen and sometimes prealbumin as well. These results also support the earlier suggested hypothesis that the prealbumin may act as a hapten carrier protein.

Binding Sites, Antibody↗
PubMed1977

Purification of prealbumin from human and canine serum using a two-step affinity chromatographic procedure.

1. A two-step-method is described by which human and canine prealbumin have been isolated from serum in good yield and high purity. The first step involves binding and release of prealbumin by a thiol-disulfide interchange reaction with thiol-Sepharose 4B. The second step consists of reversible binding of prealbumin to retinol-binding protein covalently linked to Sepharose 4B. 2. The canine prealbumin was immunochemically identified as an alpha2-globulin. Like human prealbumin it is a tetramer with some 10% smaller subunits than human prealbumin. Both proteins are devoid of carbohydrate and both bind thyroxin.

Animals↗
PubMed1977

Affinity labeling of human serum prealbumin with N-bromoacetyl-L-thyroxine.

Affinity labeling of human serum prealbumin with N-bromoacetyl-L-thyroxine (BrAcT4) was used to investigate the binding domain for L-thyroxine (T4) on prealbumin. Fluorescence titration with 8-anilinonaphthalene-1-sulfonate revealed a strong and a weak binding site for BrAcT4 (K1 = 1 X 10(8) M-1; K2 = 1 X 10(6) M-1). The reaction of BrAcT4 with prealbumin to form a covalent bond was inhibited in the presence of T4 and binding of T4 to prealbumin was nearly abolished after affinity labeling with BrAcT4. Affinity labeling with 2 mol of BrAcT4/mol of prealbumin resulted in covalent binding of 1 mol of ligand. Acid hydrolysis of affinity-labeled prealbumin gave Nepsilon-carboxymethyllysine and iminodiacetic acid, the latter being derived from the NH2-terminal glycine. A combination of analytical procedures, including tryptic digestion after maleylation, cyanogen bromide cleavage, digestion with yeast protease C, and sequential Edman degradations, revealed that the Nepsilon-carboxymethyllysine was derived from lysine-9 and lysine-15 and that the affinity label had distributed itself among glycine-1, lysine-9, and lysine-15 in a ratio of 29:63:8.

Affinity Labels↗
PubMed1978

Thyroxine-induced conformational changes in prealbumin.

The effects of thyroxine binding on the conformation of human prealbumin and bovine serum albumin have been examined. A blue shift in protein absorption was observed with prealbumin, whereas a red shift was observed with bovine serum albumin. In the case of prealbumin, where the two binding sites are identical, the total absorption change was confined to the binding of the first ligand and has been interpreted as resulting from a conformational change. A blue shift observed in the absorption spectrum of thyroxine, however, was the same for the first and second bound molecules. These data have been interpreted in terms of two identical and interacting sites on prealbumin and explain the origin of the difference in binding affinities between the first and second sites. Fluorescence quenching by thyroxine and thyroxine effects on tryptic hydrolysis of prealbumin are in accord with the above interpretation.

Humans↗
PubMed1978

Amyloid fibril protein related to prealbumin in familial amyloidotic polyneuropathy.

Amyloid fibrils were concentrated from the kidney, thyroid, and peripheral nerve of six patients with familial amyloidotic polyneuropathy (FAP). The fibril concentrates were solubilized in 6 M guanidine.HCl and fractionated on Sephadex G-100 columns. The elution profile of all FAP amyloid fibril concentrates revealed a protein of apparent Mr of 14,000, designated the FAP protein, that was absent from normal human tissues treated by the same procedure and from fibrils of a primary amyloidosis liver. Antisera against whole denatured fibril concentrates prepared in rabbits reacted with the FAP protein and a component in normal human serum corresponding to prealbumin. It was further established that the FAP protein shared common antigenic determinants with human prealbumin by its reaction of identity with normal prealbumin using commercial antisera against human prealbumin. Amyloid AL or AA proteins could not be identified in FAP fibrils by sensitive immunochemical assay methods. These results suggest that the FAP protein is a unique and significant component of the FAP amyloid fibrils and that it is closely related to the 13,745 Mr prealbumin subunit.

Amyloid↗
PubMed1975

Plasma vitamin A, retinol-binding protein and prealbumin concentrations in protein-calorie malnutrition. III. Response to varying dietary treatments.

Plasma vitamin A, retinol-binding protein, and prealbumin concentrations have been studied in 38 northern Thai children with protein-calorie malnutrition (PCM). The 4-week study period consisted of 1 week of stabilization followed by 3 weeks of treatment with formula diets varying in their protein and calorie content. The stabilization period comprised 7 days of initial treatment with fluids, antibiotics, and a gradually increasing intake of protein and calories to a final level of 1 g protein and 100 kcal/kg of body weight. During this period vitamin A, retinol-binding protein and prealbumin levels all showed significant increases compared to admission values, whereas plasma albumin and total protein did not change. During the subsequent 3 weeks, the effects of four different dietary regimens, with daily calorie and protein intakes of 100 or 175 kcal/kg and 1 or 4 g/kg, respectively, were studied. Significant increases in plasma total protein concentration were seen in each of the four test groups, and increases in plasma albumin and prealbumin were also seen in three of the four test groups, and increases in plasma albumin and prealbumin were also seen in three of the four test groups (all but the 175 kcal-1 g protein group). Significant increases in plasma vitamin A levels were not seen in any of the groups. The higher protein regimens (4 g/kg per day) resulted in much greater increases in plasma albumin and total protein levels than did the lower protein regimens. No significant differences in the changes in retinol-binding protein or vitamin A levels were apparent between the test groups. Sixteen additional children with both clinical vitamin A deficiency and protein-calorie malnutrition showed significant increases in total plasma vitamin A concentrations 24 hours after the intramuscular injection of 100,000 IU water-miscible vitamin A palmitate, without a change in plasma retinol-binding protein concentrations. These studies demonstrate that plasma retinol-binding protein and prealbumin concentrations are more rapidly responsive and sensitive to dietary protein intake than is plasma albumin concentration. Furthermore, the absence of a 24-hour rise in plasma retinol-binding protein after parenteral vitamin A provides further evidence that hepatic retinol-binding protein synthesis is impaired in protein-calorie malnutrition.

Blood Proteins↗
PubMed1979

Interaction between prealbumin and retinol-binding protein studied by affinity chromatography, gel filtration and two-phase partition.

The interaction between prealbumin and apo or holo retinol-binding proteins has been studied by affinity chromatography, gel filtration and two-phase partition. At physiological ionic strength apo and holo retinol-binding protein form 1:1 molar complexes with prealbumin. Mean dissociation constants for the prealbumin compex with apo retinol-binding protein and holo retinol-binding protein with all-trans retinol, retinoic acid, retinal and retinyl acetate were calculated from the partition data as 0.33 +/- 0.11 x 10(-6) M and 0.075 +/- 0.015 x 10(-6) M respectively (mean +/- S.E.M.). The difference was statistically significant. Quantitative data on the amount of retinol, retinol-binding protein and prealbumin in plasma and urine were in good agreement with the ratio of the dissociation constants for the complexes of apo and holo retinol-binding proteins with prealbumin as determined in the partition experiment. The magnitude of the dissociation constants was compatible with previously published data on the turnover of retinol-binding protein.

Aged↗
PubMed1976

Comparative studies of human and chicken retinol-binding proteins and prealbumins.

Microheterogeneity of retinol-binding proteins of human plasma and urine, and of chicken plasma was studied by polyacrylamide gel electrophoresis. All three protein systems were found microheterogenous. Incorporation of retinol into the protein preparations on the one hand, and depletion of these proteins from retinol on the other hand, enabled us to clarify the extent to which the presence or absence of the ligand affects the apparent heterogeneity. Upon electrophoresis, each of the native proteins displayed two pairs of protein zones. It appeared that within each pair the fast moving band corresponded to aporetinol-binding protein which upon binding of retinol was converted to a holoprotein with a slightly lower mobility. However, it did not seem that proteins of one pair were converted to proteins of the second pair upon binding of retinol, substantiating ghe microheterogenous character of this protein system. A rapid, two step procedure for isolation of prealbumins from plasma is described. The method which consists of DEAE-cellulose chromatography follwed by preparative electrophoresis was utilized to separate human and chicken prealbumins. Routine dodecyl sulphate electrophoresis resulted in partial dissociation of human prealbumin but in no dissociation of the chicken protein. More drastic treatments prior to electrophoresis were needed to effect complete disruption of both proteins into subunits.

Animals↗
PubMed1977

Protein-DNA and protein-hormone interactions in prealbumin: a model of the thyroid hormone nuclear receptor?

High resolution X-ray analysis of the hormone-binding protein prealbumin has shown that it has a structural complementarity to double-helical DNA. The proposed binding site is composed of two symmetry-related beta-sheets containing a pair of helically disposed arms, which can interact with the bases in the wide groove of DNA. A palindromic target sequence is indicated by the symmetry of the protein. The two identical thyroid hormone binding sites on prealbumin are located in a channel that runs completely through the molecule. These two structural features suggest prealbumin as a model for the thyroid hormone nuclear receptor, providing a number of detailed predictions of its properties.

Amino Acid Sequence↗
PubMedDate not supplied

[Antigenic composition of prealbumin fraction of bull brain water-soluble proteins].

The antigenic composition was studied in the fraction of prealbumins obtained by preparative electrophoresis in the agar hel of proteins salted out from the aqueous extract of bull cerebral hemispheres with amminiom sulphate within saturation limits of 60-100% (fraction 0.6-1). The chickens antisera immunized with the fraction of bull brain prealbumins were used in the experiment. One organospecific and species-nonspecific antigen called the antigen D is found by the method of immunoelectrophoresis in the components of the prealbumin fraction by means of the antisera obtained. This antigen is detected in water-soluble proteins of the bull great cerebral hemispheres and optic nerve. The antigen immunologically identical to that of the bull is contained in the aqueous extract of the rabbit and rat brain and is not found in the chicken brain.

Animals↗
PubMed1977

[Investigation of rat brain prealbumins].

12 prealbumines of rat brain water-soluble fraction were studied. Neither lipid components nor carbohydrate ones were found out in the proteins. Three of the proteins appeared to be RNA-proteids. Their subcellular distribution was investigated. The effects of temperature, salts, acids and ethanol on disc electrophoretic spectrum of brain prealbumines were closely observed. The amino acid composition, properties, compartmentation, tissue and species specificity of one of the prealbumines were studied in detail. The protein is marked as BTB-protein, as it migrates under disc electrophoresis in 7,5% polyacrylamide gel with the "witness" front of bromothemol blue (BTB). The content of BTB-protein is 0.06--0.08 gr per 100 gr of wet tissue. The protein is RNA-proteid. Its molecular weight is 10,000--20,000. BTB-protein contains 42 mole % of acidic amino acids and 5.4 mole % of alkaline ones. The protein was found in nuclear and cytoplasmic fractions. It is mainly an all-organs protein. Small amount of this protein is found in blood serum. BTB-protein can be found on the disc electrophoregramms of embryo and newborn rats brain proteins, as well as of the brain of other mammals, birds and amphibia. BTB-protein is resistant to boiling and to the effects of salts, acids, ethanol. It is suggested that BTB-protein has heterogenous structure and may be of neurophysin nature.

Amino Acids↗
PubMed1979

[Variations of various plasma (albumin, prealbumin, retinol binding protein), and urinary parameters during measles in Senegalese children].

In order to evaluate the effect of measles on proteins carrying vitamin A, we have examined 58 children with measles (24 have been seen again 2 weeks later) and 52 healthy controls of similar age and nutritional status. During the course of fever we have observed a high urinary excretion of urea and creatinine with proteinuria while the hydroxyproline index is significantly lower than in the controls. Irrespective of the nutritional status the plasma levels of albumin, prealbumin and R.B.P. are consistantly low. Two weeks later, while the albumin level has decreased, the other parameters are aiming towards normal values. The higher levels of prealbumin and R.B.P. suggest a reactivation of the hepatic protein synthesis. The urinary excretion of R.B.P. has not changed significantly during measles. We have observed rather high urinary losses of R.B.P. in the controls. The low levels of plasma prealbumin possibly do not allow the complete binding of the R.B.P.

Age Factors↗
PubMed1975

Negative cooperativity in the binding of thyroxine to human serum prealbumin. Preparation of tritium-labeled 8-anilino-1-naphthalenesulfonic acid.

The binding of thyroxine (T4) and 8-anilino-1-naphthalenesulfonic acid (ANS) to human serum prealbumin was measured by equilibrium dialysis at pH 7.4 in 0.05 M phosphate-0.10 M NaCl at 25 degrees. The data were analyzed for the binding constants based on equations for (1) two independent sites and (2) two identical sites with negative interaction. Evaluation by the independent site model gave the following association constants: for T4 binding, KT1 = 1.0 x 10-8 M-1, KT2 = 9.5 x 10-5 M-1; for ANS binding, KA1 = 9.5 x 10-5 M-1, KA2 = 2.1 x 10-5 M-1. The interactive model gave constants kT = 5.5 x 10-7 M-1 and kA = 5.5 x 10-5 M-1. Interaction factors, alpha, defined such that -RT in alpha is the energy of interaction, were: alpha T = 0.041 AND ALPHA A = 0.62 for T4 and ANS, respectively. The "best fit" values for the number of sites were 2.0 and 1.6 for T4 and ANS, respectively. The binding of T4 to human prealbumin was competitive with ANS, and the binding constants evaluated from competition experiments were in agreement with those found for each ligand when studied separately. On the basis of analysis of X-ray data of human prealbumin (Blake et al.) there appear to be two identical T4 sites. It is therefore evident that the binding of T4 represents a case of negative cooperativity which is presumably due to interaction between ligands.

Anilino Naphthalenesulfonates↗