High Molecular Weight Protein Fraction Research Articles

Effect of cadmium on the toxicity of lanthanons in mice and rats

Prior administration of a sublethal dose of cadmium (1 mg/kg i.p.) produced a significant reduction in mortality of male mice and a trend to improve the impaired drug-metabolising capacity in male and female rats after a toxic dose of the light lanthanon, cerium (2 mg/kg i.v.). Gel filtration studies show that cerium binds to the high molecular weight protein fraction in rat liver cytosol despite cadmium pretreatment. This finding rules out the possibility that cadmium exerts its effect through the protective system of a newly synthesized metallothionein.

Photochemical Changes in Major Whey Proteins of Cow's Milk

Catalytic photoaggregation and photodegradation of purified α-lactalbumin, β-lactoglobulin, and acid whey proteins isolated from homogenized milk were studied. Disc gel electrophoresis of fluorescent light- and sunlight-exposed α-lactalbumin resulted in the formation of high molecular weight protein fractions with a corresponding decrease in the major protein band. When β-lactoglobulin was treated and analyzed similarly, high molecular weight proteins appeared with a concurrent decrease in the major band. Light-exposed whey had diminished intensities in all the bands. Riboflavin was necessary to catalyze the photochemical changes in the proteins. Gel filtration chromatography with Sephadex G-75 of purified protein samples and acid whey demonstrated an increase in a high molecular fraction indicating aggregation of protein following exposure. Lowry assay of exposed protein fractions confirmed photoaggregation, and N-group analysis provided supporting evidence of peptide bond hydrolysis.

Induction and Biochemical Parameters of Callus Growth from Three Peanut Cultivars1

Abstract The phytohormones 2,4-dichlorophenoxyacetic acid, naphthalene acetic acid and kinetin nave been employed to induce callus growth from the cotyledon tissue of three commercial peanut cultivars: ‘Early Bunch’ (EB), ‘NC-Fla 14’ (NC) and ‘Florunner’ (FR). Cultivar specific parameters have been examined for both cotyledon and callus tissue. The relative growth rates of callus tissues were always EB>NC>FR. SDS-polyacrylamide gel electrophoresis performed on the proteins from both types of tissue demonstrated mat most cultivar specific differences seen in cotyledon tissue are maintained by callus tissue from the same plant. However, more high molecular weight protein fractions were observed in cotyledon tissue than in callus. Amino acid analysis of these tissues revealed a higher concentration of neutral and aromatic amino acids in cotyledon while callus tissue was higher in basic amino acids.

A high molecular weight phosphoprotein in cultured fibroblasts that associates with polymerized tubulin

Microtubule associated proteins (MAPs) are high molecular weight proteins that associate with microtubules during polymerization. This report describes a high molecular weight protein fraction with a molecular weight of approx. 290 000 from cultured mammalian fibroblasts that associates with polymerized rat brain tubulin. This protein(s), which is referred to as f-MAP, is enriched approx. 25-fold in a twice polymerized microtubules when compared with the original cell extract. Polymerization of rat brain extract in the presence of in vivo 32P-labeled fibroblast extract reveals the presence of a 32P-labeled protein in the polymerized pellet with the same electrophoretic mobility as f-MAP. The present study suggests that fibroblasts in culture contain a high molecular weight phosphoprotein with properties and a molecular weight very similar to the MAPs described in mammalian brain.

High molecular weight protein aggregates in X-ray-induced cataract

The nature and the possible mechanism of formation of high molecular weight (HMW) protein aggregates were studied in X-ray-induced cataract in rabbit. The HMW protein fraction (molecular weight >4×10 6 daltons) which constituted approximately 18% of the total soluble protein in both the cataractous cortex and nucleus was isolated by gel filtration chromatography. The concentration of sulfhydryl (-SH) groups per milligram of protein in the HMW fraction was three times higher than that of normal α-crystallin. In addition, 50% of the total concentration of sulfhydryl groups contained in the HMW protein was found to be present in the oxidized state; the increased oxidation of protein -SH groups in the X-irradiated lens being observed only during the final stage of cataract which was marked by complete opacity. Treatment of HMW protein with dithioerythritol and subsequent refractionation yielded two peaks; peak I which eluted as α-crystallin and the second fraction (peak II) which eluted in the position of low molecular weight β-crystallin. Peak I accounted for approximately 40% of the deaggregated protein and peak II 60%. There was little protein eluted in the position of γ-crystallin. Thus, it appears that the HMW protein of X-ray-induced cataract is comprised of both α- and β-crystallins joined by intermolecular disulfide bonds. SDS (sodium dodecyl sulfate) electrophoresis of HMW protein and peaks I and II showed that the major bands of both peaks I and II were represented in the bands exhibited by the HMW protein. The electrophoretic mobilities of the major bands of peaks I and II were similar to those of α-crystallin and β-crystallin, respectively. The amino acid composition of peak I was found to be comparable to α-crystallin while the composition of peak II was similar to β-crystallin with the major exception that the hydrolysates of proteins in both peaks I and II were nearly lacking in tyrosine.

Chronic copper poisoning in sheep. ii. The distribution of soluble copper-, molybdenum-, and zinc-binding proteins from liver and kidney.

The concentrations of copper, molybdenum, and zinc in the soluble protein fraction from sheep liver and kidney were determined after gel filtration. Samples from grazing sheep as well as from copper poisoned sheep were tested. In normal sheep the copper-binding proteins were separated into 3 different fractions. In copper poisoned sheep, as well as in grazing sheep with high copper concentrations, only 2 main fractions were seen. Molybdenum was only found in the high molecular weight protein fraction. The distribution of the zinc-binding proteins varied according to the degree of copper accumulation. The low molecular weight zinc-binding protein fraction was only seen in sheep with liver copper concentrations lower that 40 mug/g wet weight. In copper poisoned sheep a major part of the kidney copper was found in the low molecular weight protein fraction. At post mortem the bile copper concentrations in the copper poisoned sheep were only 2-4 times higher than those of the control animals.

Zinc-hemocyanin binding in the hemolymph of Carcinus maenas (Crustacea, Decapoda)

1. 1. A quantitative and electrophoretic study of copper and zinc in hemolymph of the crustacea decapoda, Carcinus maenas, has been carried out. 2. 2. Most of the copper was linked with hemocyanin. 3. 3. All copper-binding proteins are hemocyanin. 4. 4. Zinc belongs to three different compartments: more than 68% is linked with hemocyanin; about 10% is shown in the fraction containing blood cells, lipids and carotenoids; 15% is present in the hemolymph under a soluble and dialysable form. 5. 5. Specific zinc-binding protein has not been found out in the serum of Carcinus maenas. 6. 6. Zinc linked with hemocyanin is found on high molecular weight protein fractions only.

The high molecular weight proteins released from cultured cells

Studies have been performed with the serum-free culture medium taken from several fibroblast monolayer culture lines. A high molecular weight protein fraction was separated from the concentrated medium by sucrose density gradient centrifugation. Polyacrylamide gel electrophoresis was used to assess the degree of purification obtained. In the electron microscope the negatively stained high molecular weight proteins were found to closely resemble the α 2-macroglobulins. The suggestion that these proteins from cultured cells resemble the cylindrical protein complex isolated from mammalian erythrocyte ghosts is not supported by this study. The results are discussed in the light of the extensive literature now available on the electron microscopy of high molecular weight proteins.

Normalizing effect of taurine on the lens permeability changes to rubidium due to phospholine iodide

Assays were carried out to determine the trypsin inhibitor activity present in the water-soluble and water-insoluble fractions of human lenses of various ages. Little change was seen in the inhibitor activity of the water-soluble protein fraction. When this fraction was chromatographed on an Agarose A-1·5 m column, however, the inhibitor activity was increasingly associated with the high molecular weight (HMW) protein fraction with age. A gradual increase in water-insoluble inhibitor was seen up to age 60, which correlated with the increase in protein in this fraction. After age 60, a marked increase in the water-insoluble inhibitor activity was observed. In 80–90-yr-old lenses. 1 mg of water-insoluble protein was able to inhibit 200 μg of crystallin trypsin by 50%. Similar assays on a collection of cortical and brunescent cataracts also showed very high levels of water-insoluble inhibitor activity. In most cases, these values were higher than those for age-matched control lenses. Fractionation of the water-insoluble proteins showed that the bulk of the activity remained with the urea-insoluble fraction in cataractous lenses. A low molecular weight trypsin inhibitor was isolated from the water-soluble and water-insoluble fractions of human lenses. An age-dependent increase in this inhibitor was observed by activity measurements and electrophoretic analysis.

Anaphylactogenic properties of bee venom and its fractions

I have investigated the anaphylactogenicity of whole bee venom and its pure protein and peptide components (phospholipase A, melittin and apamin) and the partially purified protein and peptide fractions (the highest-molecular weight fraction I, hyaluronidase, fractions Op, P 1 and P 2 and protease inhibitor) obtained by means of gel-filtration and ion-exchange chromatography. Anaphylactogenicity was observed with the whole bee venom and the high molecular weight protein fractions—fraction I, phospholipase A and hyaluronidase. The peptides melittin, apamin, fraction Op (mast cell degranulating peptide, MCD) and fractions P 1 and P 2 did not show any anaphylactic properties after sensitization with or without Freund's complete adjuvant.

Conversion of a weak flour to a strong one by increasing the proportion of its high molecular weight gluten protein

AbstractA weak, over‐extensible flour was modified by additions of gluten fractions which had been obtained from the same flour. The physical dough‐testing characteristics of a strong, well‐balanced flour could be closely matched by additions of a suitably proportioned mixture of the whole gluten and a high molecular weight protein fraction of the gluten, prepared by fractional extraction.

Are mycoplasma membrane proteins affected by variations in membrane fatty acid composition?

1. 1. The influence of the fatty acid composition of membrane lipids on the quantitative distribution of membrane protein of Mycoplasma laidlawii has been investigated. 2. 2. Cells were grown in media supplemented with either a saturated fatty acid (palmitic acid or stearic acid) or an unsaturated fatty acid (palmitoleic acid or oleic acid). Lipids isolated from membranes of these cells were markedly enriched in the supplemented fatty acid. 3. 3. The proteins of the different types of membranes were analyzed by sodium dodecyl sulfate-acrylamide-gel electrophoresis of membranes from cells grown in the presence of radioactively labelled amino acids. In general, protein composition and relative abundance were unaffected by fatty acid variation. One high molecular weight protein fraction was present in higher concentration in membranes rich in saturated fatty acids than in those rich in saturated fatty acids. 4. 4. The membranes rich in saturated fatty acids were also found to have a slightly higher density as determined by isopycnic centrifugation.

The absence of α-keto acids in polymeric collagen

1. 1. The presence of α-keto acids in the telopeptide region of polymeric and monomeric collagens has been studied. 2. 2. Collagen was digested in the native state by pronase, and the high molecular weight protein fractions were removed by dialysis or precipitation. Carbonyl-containing components (including α-keto acids) in the diffusate or supernatant were assayed as DNP-hydrazone derivatives. 3. 3. Very small quantities of 5 to 6 DNP-hydrazone derivatives were obtained, but extensive control studies indicated that they were not derived from integral components of either polymeric or monomeric collagen. 4. 4. Subsidiary experiments indicated that the DNP-hydrazone derivatives arose from small quantities of impurities present in the buffer, collagen preparations and dialysis membrane, but more especially from pronase which (a) could convert l-alanine to the corresponding α-keto acid, pyruvate, and (b) contained DNP-hydrazine-reactive components.

Biosynthesis and release of neurophysin.

In vivo labeling of protein of the hypothalamo-neurohypophysial tract was accomplished by slow infusion of 35S-cysteine into the third ventricle of dehydrated dogs. In shortterm experiments hypothalamo-median eminence tissue was found to contain labeled protein which possessed chemical and serological properties very similar to those of bovine neurophysin. The subcellular distribution of this material paralleled the distribution of vasopressin. When the animals were permitted to survive 10–21 days with free access to water, labeled neurophysin was found in their posterior pituitary glands. When hemilobes of these glands were incubated in vitro and challenged with elevated K+, there occurred a simultaneous increase in the release of radioactive vasopressin and neurophysin into the incubation medium compared with the amounts released during incubation in media containing either low K+ or high K+ in the presence of Mg++. Some evidence was also obtained for simultaneous release in vivo of hormone and carrier protein into the blood stream by comparing the content of radioactive protein in plasma immediately before and after hemorrhage of 2 dogs which had previously received intraventricular infusion of 35S-cysteine. The results presented in this paper, together with the findings of other investigators concerning changes in the levels of neurophysin-like proteins in the posterior lobe, are highly suggestive of simultaneous biosynthesis and release of the hormones of the neurohypophysis and their carrier proteins. The high molecular weight protein fraction which accompanies beef neurophysin prepared by salt fractionation was found to be immunologically unrelated to the hormone-binding proteins. (Endocrinology83: 1299, 1968)

Salicylates and Iron Absorption

Summary The administration of a salicylate-iron complex in a 50:1 molar ratio did not alter radioiron absorption in normal subjects. Although salicylate has the ability to chelate iron in vitro, its ineffectiveness in vivo was shown to be due to the stronger affinity of gastric juice for iron. A high molecular weight protein fraction in gastric juice successfully competes with salicylates for the iron, rendering the salicylate ineffective in iron absorption. No evidence was found to support the proposal that a mechanism for a salicylate anemia is the formation of an inhibitory iron-salicylate complex.