Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UMLS:C0272170 (SDS)
 50,377 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A bovine lens "native" plasma membrane fraction containing its full compliment of extrinsic proteins was prepared by sucrose density centrifugation of the water insoluble fraction. The major membrane fraction was found at the 25/45% sucrose interface. This fraction contained 73% of the total water insoluble phospholipid, 74% of the total water insoluble cholesterol and 58% of the total urea-insoluble protein. Only 9% of the total urea-soluble protein was membrane associated (extrinsic protein), most (75%) was recovered from the pellet. The major intrinsic protein (8 M-urea-insoluble) of the membrane fraction was MIP28, with lesser amounts of MP17. Extrinsic proteins (8 M-urea-soluble) were examined by SDS-PAGE, isoelectric focusing, immunoblotting and amino acid composition analysis. Approximately 70% of the total extrinsic protein appeared to be alpha A-crystallins and modified alpha A-crystallins. About 20% of the extrinsic protein was apparently beta- and gamma-crystallins. The remainder contained presumed cytoskeletal proteins and perhaps other unidentified polypeptides. The native plasma membrane was found distributed throughout the lens with only minor differences in the quantitative composition of the membrane fraction. We have concluded that the native membrane fraction represents the lens plasma membrane with its extrinsic proteins which exist in vivo. These extrinsic proteins appeared to be primarily acidic alpha-crystallin polypeptides with minor amounts of beta- and gamma-crystallins, and presumed cytoskeletal elements. We speculate that these extrinsic proteins may serve as a nucleation site for the association of other water insoluble protein through protein-protein interactions such as those found in the non-membrane associated urea-soluble protein. Together, these interactions may form a structured cytoplasmic matrix important for the maintenance of lens transparency.
 ...
PMID:Examination of a lens 'native' plasma membrane fraction and its associated crystallins. 142 20

Plasma membrane with its associated extrinsic proteins was isolated from normal and cataractous rat lenses by centrifugation of the total water insoluble fraction from homogenized lenses on a discontinuous sucrose gradient. Membrane, which we call "native" membrane, was recovered mainly from the 25/45% sucrose interface. Development of the experimental U18666A cataract resulted in plasma membrane shifting to higher density (the 50/55% sucrose fraction) and great increases in the urea soluble protein content of the lens. At early stages of cataract development, most of the increased urea soluble protein was membrane associated, presumably as extrinsic protein. With advancing cataract, most of the urea soluble protein appeared in an essentially membrane-free pellet fraction. The urea soluble protein associated with the cataract membrane was shown by combined IEF, SDS-PAGE, Western blotting, amino acid compositional analysis and protein sequence determinations to be mainly composed of modified alpha- and beta-crystallins. Alpha A-crystallin truncated by not more than 27 residues from the carboxyl terminus plus beta b1 crystallin truncated by 49 residues from the amino terminus were conclusively identified. In addition to beta b1, a population of six alpha-crystallin derived polypeptides were specifically enriched in the cataract membrane fraction. Four of these six alpha-crystallins appear to be truncated from their carboxyl terminus, a modification which should have increased their hydrophobicity. The pellet fraction, which accumulated in the lens nucleus as the cataract advanced, was enriched in urea soluble gamma-crystallin derived polypeptides. We suggest that protein insolubilization in this experimental cataract involves the selective and tight association of principally modified alpha-crystallins to the fiber cell plasma membrane.
 ...
PMID:Selective association of crystallins with lens 'native' membrane during dynamic cataractogenesis. 142 24

Nascent synthesis and accumulation of germin and its mRNA mark the onset of renewed growth when wheat embryos are germinated in water. Germin is a water-soluble, pepsin-resistant protein that is not found in immature embryos, or in mature embryos before their germination. An antiserum was raised by injecting rabbits with germin that was freed of other proteins by pepsinization and gel filtration. The antiserum has been used to detect, in extracts of mature embryos from dry, ungerminated wheat grains, a protein that is antigenically related to germin. The antigenically related protein has been named pseudogermin. Pseudogermin accumulates, maximally, between 20-25-days postanthesis, then declines appreciably in amount by 30-days postanthesis, in soluble extracts of immature embryos from several wheat varieties. The antiserum was also used to identify germin and pseudogermin among the proteins extracted from cell walls and to bind immunogold to cell walls preparatory to visualizing freeze-cleaved embryos by scanning electron microscopy. Wall-associated germin accounts for about 40% of the total germin in germinating wheat embryos. Appearance of germin in the apoplast is the most conspicuous germination-related change in the distribution of cell-wall proteins. It seems that germin may act at the level of the apoplast and that pseudogermin may subsume the role of germin at low water potentials during embryogenesis. The N-terminal eicosapeptide sequences in germin and pseudogermin are very similar but SDS/PAGE analysis detects discrete differences between the mobilities of their constituent monomers as well as gross differences between the stabilities of the parent oligomers. Like germin, pseudogermin is a water-soluble, pepsin-resistant protein, but pseudogermin has unprecedented disulphide-independent thermostability properties that have never been previously reported for a water-soluble oligomeric protein. Polysaccharides that co-purify with otherwise pure specimens of germin (and pseudogermin) have been isolated for analysis and shown to be highly substituted glucuronogalactoarabinoxylans. The possible biological significance of selective and tenacious association between germin and glucuronogalactoarabinoxylans is discussed in relation to cell expansion during embryogenic and germinative development of wheat, as are some peculiarities of amino-acid sequence that suggest a possible relation between germin and a proton-specific ion pump: gastric ATPase.
 ...
PMID:Germin isoforms are discrete temporal markers of wheat development. Pseudogermin is a uniquely thermostable water-soluble oligomeric protein in ungerminated embryos and like germin in germinated embryos, it is incorporated into cell walls. 142 3

Calpains are calcium-activated neutral proteases found in many tissues including the lens. The purpose of this research was to localize calpain in various biochemical fractions of the rat lens. Lenses were homogenized (with and without added calcium) and separated into water-soluble and -insoluble fractions, which were further extracted with urea, NaOH, and SDS. Of the total calpain 10% was insoluble. In the lens calpain was found to be both insoluble and associated with the membrane. Extraction of calpain from the insoluble fraction suggested calpain was loosely and tightly associated with the membrane. Calpain associated with membrane-rich fractions was obtained from discontinuous sucrose gradients, confirming the above. Calcium increased the amount of calpain associated with the insoluble fraction up to 30% of the total calpain. When the calcium was chelated, this calpain once again became soluble, and its specific activity was higher than water-soluble calpain. The translocation of calpain from the water-soluble fraction to insoluble fractions by calcium may be important because: (1) it may bring calpain into proximity with its substrates; and (2) it may activate calpain, since membrane phospholipids lower the protease's calcium requirement.
 ...
PMID:Association of calpain with insoluble pellet of rat lens. 142 69

Antidiuretic hormone (ADH) increases toad bladder granular cell apical membrane osmotic water permeability (Pf) by insertion of cytoplasmic vesicles containing water channels into the apical membrane. Termination of ADH stimulation results in endocytosis of water channel-containing membrane. In previous work, we have purified water channel-containing vesicles and demonstrated that they contain 12 major protein bands when analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). On the basis of vectorial labeling studies of granular cells and purified vesicles, we have proposed previously that vesicle proteins of 55, 53, and 17 kDa are ADH water channel components. In this report, we have purified and analyzed these three proteins using a combination of SDS-PAGE, peptide mapping, amino acid composition, and amino-terminal analyses. The 55- and 53-kDa proteins are distinct protein species possessing a high degree of structural similarity. Both possess a large content of cysteine. The 17-kDa protein appears to be a proteolytic fragment of the 53-kDa protein. None of these three proteins is phosphorylated or contains large amounts of covalently linked carbohydrate. ADH-elicited Pf is inhibited by the organic mercurial reagent fluorescein mercuric acetate (FMA). Exposure of water channel-containing vesicles to FMA labels selectively four vesicle proteins of 92, 55, 53, and 29 kDa while reducing vesicle Pf by 82%. The combination of FMA and 2-mercaptoethanol or exposure to another mercurial reagent, n-ethylmaleimide, does not inhibit vesicle Pf. Together, these data provide additional evidence for the role of the 55- and 53-kDa proteins as components of the ADH water channel. These candidate ADH water channel proteins are distinct from a 28-kDa candidate water channel protein (CHIP 28) isolated recently from human erythrocyte membranes and kidney proximal tubule by Agre and co-workers (Preston, G. M., Carroll, T. P., Guggino, W. B., and Agre, P. (1992) Science 256, 385-387).
 ...
PMID:Purification and partial characterization of candidate antidiuretic hormone water channel proteins of M(r) 55,000 and 53,000 from toad urinary bladder. 142 63

Gibberellic acid (GA3) brought about a 3-fold stimulation of AdoMet synthetase activity in wheat aleurones. At the qualitative level, three isozymes of AdoMet synthetase were observed by DE-52 chromatography in GA3-treated wheat aleurones. In contrast, the control wheat aleurones showed a single isozyme. Thus the phytohormone (GA3, 1 microM) induced two additional isozymes of AdoMet synthetase in wheat aleurones. The activity of all the three isozymes in GA3-treated aleurones was considerably decreased by the simultaneous presence of abscisic acid (ABA, 10 microM). Cycloheximide (20 micrograms/ml) also significantly lowered the levels of the three isozymes of AdoMet synthetase in Ga3-treated aleurones, thereby suggesting the requirement of de-novo protein synthesis for the complete induction of isozymes. However, wheat aleurones excised from embryonated wheat seeds, did not require the application of GA3 for the induction of two additional isozymes of AdoMet synthetase. Apparently, the transport of GA3 from the embryo to aleurones induced two new isozymes of AdoMet synthetase. Three isozymes of AdoMet synthetase were also observed in wheat embryos excised from germinated wheat grains, without exogenous application of GA3. The molecular weight of all the three isozymes of AdoMet synthetase in wheat system is 181,000. The molecular weight of the subunit of the enzyme is 84,000. The dimeric nature of AdoMet synthetase was established by SDS-PAGE analysis of the purified enzyme. In-vitro hybridization of two flanking isozymic peaks I and III by NaCl-freeze-thaw method resulted in the appearance of an additional middle activity peak (isozyme II). However, no additional isozymic peaks were generated when isozymic peaks I and III were individually given a freeze-thaw treatment. Thus the flanking isozymic peaks I and III represent homodimers that differed in their net charge. In contrast, the middle isozymic activity peak II, when subjected to NaCl-freeze-thaw treatments yielded two additional isozymic peaks, I and III, thereby suggesting its heterodimeric nature. We envisage that the three isozymes in GA3-treated wheat aleurone layers are formed by the random dimerization of two classes of enzyme subunits. The two enzyme subunits which differ in their net charge could be the product of two genes of AdoMet synthetase (SAM1 and SAM2). Based on this assumption, we propose that a single isozyme I in water imbibed control wheat aleurones is the product of SAM1 gene of AdoMet synthetase. The occurrence of three isozymes in GA3-treated aleurones could be ascribed to the expression of an alternate gene of AdoMet synthetase (SAM2 gene).(ABSTRACT TRUNCATED AT 400 WORDS)
 ...
PMID:Phytohormonal regulation of S-adenosylmethionine synthetase by gibberellic acid in wheat aleurones. 144 35

Mitochondrial succinate-ubiquinone reductase is composed of two parts, a water-soluble succinate dehydrogenase and a two-polypeptide membrane-anchoring protein fraction (QPs). The larger polypeptide of QPs is believed to be associated with cytochrome b560 (QPs1). The structure of QPs1 was studied by immunochemistry and molecular cloning and sequencing. Antibodies against QPs1 were raised in rabbits, purified, and characterized by enzyme-linked immunosorbent assay and Western blotting. The purified antibodies inhibited 75% of the reconstitutive activity of QPs and reacted with both submitochondrial particles (SMP) and mitoplasts. The binding of these antibodies to SMP was greatly increased when succinate dehydrogenase was removed from SMP by alkaline treatment, indicating that QPs1 is a transmembranous protein and that some of its specific epitopes are covered by succinate dehydrogenase. Anti-QPs1 antibodies were used to screen one cDNA clone encoding QPs1 from a bovine heart cDNA lambda gt11 expression library. The cDNA insert is 946 base pairs with an open reading frame of 396 base pairs that encodes for 132 amino acid residues. The molecular weight of QPs1, calculated from the deduced amino acid sequence, is 14,320. Although the apparent molecular weight of QPs1, estimated by high resolution SDS-polyacrylamide gel electrophoresis, is approximately 11,000, the existence of a presequence was ruled out by mass spectrometric analysis of protein fragments. QPs1 is a very hydrophobic protein. Three probable membrane-spanning segments were revealed by a hydropathy plot of the sequence. QPs1 has a higher sequence similarity to the sdhC peptide of Escherichia coli than to the sdhC peptide (cytochrome b558) of Bacillus subtilis. Like the bacterial proteins, QPs1 has 2 conserved histidines at positions 34 and 90. The conserved nature and similar location of these 2 histidines, on the matrix-side surface of the membrane, suggest that they are involved in heme ligation of cytochrome b560.
 ...
PMID:Cytochrome b560 (QPs1) of mitochondrial succinate-ubiquinone reductase. Immunochemistry, cloning, and nucleotide sequencing. 144 96

Studies were carried out comparing the ability of urea extraction and sonication to solubilize the water-insoluble (WI) protein fraction from human lens tissue. Sonication and urea extraction were able to solubilize greater than 80% of the insoluble protein whether whole lenses or lens nuclei were used. This was true for normal lens and +1 cataracts; however, only 60% solubilization was obtained with the WI fraction from more advanced cataracts. Equal aliquots of a WI fraction from both pooled normal and pooled cataract lens nuclei were solubilized with and without reducing agents. The addition of dithiothreitol (DTT) had no significant effect on solubilization of the normal lens WI fraction. DTT did increase the protein solubilized from the cataract WI fraction by 30% with urea extraction; however, no increase was seen with sonication. When sodium borohydride was used as the reducing agent, essentially the same results were obtained. The solubilized protein populations were identical by SDS-PAGE and amino acid analysis. The addition of reducing agents had no effect on the amino acid content of the solubilized proteins with the single exception of lysine. This amino acid was markedly decreased in the proteins extracted in the presence of 40 mM sodium borohydride, but not with DTT. These data suggest that the borohydride not only increased the amount of protein solubilized, but likely also stabilized glycated lysine residues during the acid hydrolysis. Therefore, sonication readily provides a soluble preparation of the WI proteins from normal and cataract lens nuclei without the need for denaturing agents, however, disulfide-linked and lysine modified crystallins were best solubilized with urea.
 ...
PMID:Studies on the solubilization of the water-insoluble fraction from human lens and cataract. 148 36

In the mole crab Emerita asiatica, the main yolk proteins consist of two slow moving lipovitellins (Lv I and Lv II) of glycolipoprotein nature. Lv I cleaves into subunits (MW: 109,000 and 105,000) and Lv II gives rise to six subunits (MW: 65,000, 54,000, 50,000, 47,000, 44,000, and 42,000) in SDS-PAGE (with beta-mercaptoethanol). In order to observe the stability of Lv II as well as to achieve better resolution of the proteins, two different buffer systems (Phosphate buffered saline and tris-buffered saline), 40% sucrose, and glass distilled water were used as homogenizing media. Among them, better resolution was achieved with tris-buffered saline and 40% sucrose, and tris-buffered saline seems to be the ideal medium for elution of Lv II. The analysis of biochemical constituents of the major Lv II reveals a percentage composition of 69.325, 27.927, and 2.753 respectively for protein, lipid, and bound sugars. In the I stage embryo, protein comprises about 67.276%, lipid 29.65%, and bound sugars 3.015%. Vitellogenin (Vg) electrophoretically corresponding to the Lv I and Lv II was present in the female haemolymph during the entire period of embryogenesis. The number of subunits (8) of Vg in all stages remained unaltered and their approximate molecular weights were Vg1, 91,000; Vg2, 87,000; Vg3, 83,000; Vg4, 61,000; Vg5, 58,000; Vg6, 45,000; Vg7, 42,000; and Vg8, 38,000. Different proteins present in the embryos (I and IV stage) and the serum obtained from the animal carrying the I stage embryo were separated by gel-filtration in high performance liquid chromatography (HPLC). Sephadex (G-200) gel filtration chromatography was used to purify the Lv II in large quantity. Total lipid extracted from Lv II as well as the embryos belonging to different stages of development were separated into their constituent neutral, glycolipids, and phospholipids, using silicic acid column chromatography. Thin layer chromatography (TLC) was used to isolate the different phospholipids purified from various stages of embryos and Lv II. As many as seven different phospholipids were separated from Lv II and I and IX stage embryos; and whereas thin layer chromatogram of V and VI stage embryos showed six different phospholipids, embryos of VII and VIII stage contained four phospholipid species. Cholesterol, glycolipids, and individual phospholipids isolated from the Lv II and I stage embryo were quantified spectrophotometrically and the results were discussed.
 ...
PMID:Purification and characterization of vitellogenin and lipovitellins of the sand crab Emerita asiatica: molecular aspects of crab yolk proteins. 151 Aug 41

Neuronal and glial surface glycoproteins have been isolated from human foetal brains by affinity chromatography on 8 M urea or 6 M guanidine-treated Con A-Sepharose 4B at 4 degrees C and three groups of glycoproteins of molecular mass 65-73 kDa, 52-63 kDa and 43-48 kDa have been identified on SDS/PAGE. These glycoproteins exhibited anomalous behaviour on SDS/PAGE, indicating the existence of a gradation of mutually interconvertible protein-SDS aggregates in dynamic equilibrium with one another. Deglycosylation and deacylation did not alter the SDS/PAGE multiple band pattern. Purified glycoproteins contained 160 +/- 90 micrograms carbohydrate/mg protein, and a sialic acid content of 25 +/- 5 nmole/mg protein. The N-terminals were blocked. The glycoproteins moved preferentially on acid/urea/PAGE. Sepharose 6B gel filtration in the absence of lipid and detergents resolved the glycoproteins into an excluded peak I and a low molecular mass peak II. Peaks I and II were non-interconvertible on Sepharose 6B gel filtration or on reversed phase HPLC in an isopropanol/water/TFA gradient system. Both peaks rendered a single fast moving band of identical mobility on acid/urea/PAGE, suggesting that peak I was possibly a micellar aggregate of the monomeric peak II. The glycoproteins were refractory to digestion by trypsin or pronase and reacted identically towards various lectins.(ABSTRACT TRUNCATED AT 250 WORDS)
 ...
PMID:Characterization of concanavalin A-binding neuronal and glial surface glycoproteins from human foetal brain. 151 10


<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>