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At least 19 recordsLinked to original sources
PubMed1979

Identification of the subunit proteins of 10-nm neurofilaments isolated from axoplasm of squid and Myxicola giant axons.

Neurofilaments were isolated from the axoplasm of the giant axons of Myxicola infundibulum and squid. The axoplasm was fractionated by discontinuous sucrose gradient centrifugation and gel filtration on Sepharose 4B. The fractions were monitored for neurofilaments by electron microscopy. When isolated in the presence of chelating agents, the neurofilaments of Myxicola are composed almost entirely of protein subunits with mol wt of 150,000 and 160,000. Squid neurofilaments contain two major proteins with mol wt of 200,000 and 60,000. These proteins are compared with other intermediate filament proteins which have been reported in the literature.

Animals↗
PubMed1979

Electroimmunoassay of a subunit protein in a macromolecular complex (apolipoprotein B in human plasma very low density lipoprotein); implications for other electroimmunoassay systems.

With an electroimmunoassay ("rocket") system for the apolipoprotein B component of the plasma very low density lipoprotein complex we obtained results which were similar to those obtained by a colorimetric tetramethylurea extraction method. Results were up to twice as high as those using radioimmunoassay. Low density lipoprotein containing apolipoprotein B as the only demonstrable protein component was used as the standard for these assays. This protein produced larger and higher rockets at pH 8.6 when the negative particle charge was increased by maleylation. The very low density lipoprotein complex has a higher negative charge at pH 8.6 than low density lipoprotein. These findings suggest that some apolipoprotein B in vary low density lipoprotein is not "recognised" by anti-apolipoprotein B antibodies, hence radioimmunoassay results are lower than those obtained with the tetramethylurea extraction method. The higher negative charge on very low density lipoprotein particles (compared with low density lipoprotein), as a factor tending to increase rocket area and height, is counterbalanced by reduced recognition by antiapolipoprotein B antibodies. The net result of these opposing tendencies is that the rocket electroimmunoassay of apolipoprotein B in very low density lipoprotein fortuitously gives valid results, under the specified assay conditions. We conclude that electroimmunoassays of complex proteins are not necessarily valid if protein subunits are used for standards. This has implications for the electroimmunoassay of other apolipoproteins.

Apolipoproteins↗
PubMed1978

Identification of the structural gene for the hook subunit protein of Escherichia coli flagella.

Previous studies showed that the structural gene for the flagellar hook subunit protein (molecular weight 42,000) was one of a group of flagellar genes located on the Escherichia coli genome near pyrC. Several lines of evidence indicate that the flaK gene is the structural gene for the hook subunit protein. Fla+ strains that were insensitive to chi infection could be isolated as revertants of an FlaK- amber mutant strain but from no other Fla- strain. The hook subunit proteins isolated from such chi-sensitive revertants of the FlaK- strain were shown to be antigenically and electrophoretically different from the hook protein isolated from the wild-type strain. Thus, reversion of a mutation in the flaK gene resulted in alteration of the structure of the hook protein. Furthermore, in programming experiments with hybrid lambda containing flagellar genes, lambdafla with flaK genetic activity programmed the synthesis of a 42,000-molecular weight protein, whereas lambdafla without flaK genetic activity did not.

Bacterial Proteins↗
PubMed1975

Effects of dimethyl sulfoxide on subunit proteins.

The effects of DMSO are thought to result from the formation of hydrogen bonds with proton-donor groups on biopolymers, which are stronger than those formed with water. Since DMSO contains methyl groups, however, effects on hydrophobic bonding in proteins could be expected at higher DMSO levels. Our studies of the effects of DMSO on model subunit proteins can be interpreted in the above terms. At a concentration of 20% or less, DMSO changed glutamate dehydrogenase into the inactive monomer and the effects were fully reversible with the activator (ADP). Higher DMSO levels resulted in irreversible inactivation. The predominant effect noted on beta-glucuronidase was irreversible inactivation by 20% or more DMSO at 37 degrees C. Purified beta-glucuronidase exhibited an activation in 20% DMSO at high substrate levels; this resulted from an apparent substrate inhibition in the absence of DMSO. DMSO inhibited the clotting of fibrinogen by purified thrombin, but the major effect appeared to be due to competition between thrombin and DMSO for binding sites on fibrinogen. These effects appear to be largely due to interactions between DMSO and hydrophobic bonding in fibrinogen, although DMSO also appears to interfere with the aggregation of fibrin monomers through its effects on hydrophilic groups. These results suggest that reversible alterations in protein structure are the major effect of exposure of subunit proteins to low DMSO levels at low temperatues, while irreversible denaturation of subunit proteins may be an appreciable effect a higher temperatures and higher DMSO concentrations.

Adenosine Diphosphate↗
PubMed1976

A pH-dependent conformational change in the coat protein subunits from potato virus X.

Both the circular dichroism and fluorescence spectra of the dissociated coat protein subunits from potato virus X changed substantially over the pH range 8 to 4, irreversible changes resulted below pH 4, with tyrosyl and tryptophanyl residues affected most. The titration curves show a pKa of about 5.6 and do not require cooperative interactions between the coat protein subunits, thus they are in marked contrast to titrations of tobacco mosaic virus A-protein. The spectra of the intact virus were little changed between pH 8 and 4 and suggested that the coat protein was locked into a conformation similar to that of the subunits in solution at pH 7. It is proposed that the pH induced conformational change is responsible for determining the acidic branch of the pH profile for reconstitution of potato virus X from its dissociated coat protein subunits and RNA.

Circular Dichroism↗
PubMed1975

Production of ferritin by rat hepatoma cells in vitro. Demonstration of protein subunits and ferritin by immunofluorescence.

Using precipitating antibodies to ACI rat liver ferritin and to sodium-dodecyl-sulfate-dissociated protein subunits of ACI rat liver ferritin, we have demonstrated the presence of ferritin-positive sites and subunit-positive sites in situ in several rat hepatoma cell lines by immunofluorescence. Hepatoma cells from three transplantable rat hepatomas (Reuber H-139, Reuber H-35, and Morris 5123) were explanted and propagated. Rabbit antibodies specific for either protein subunits of ferritin or ferritin were prepared by affinity chromatography or by dissociation of antibody-antigen complexes with 0.1 M acetic acid followed by differential ultracentrifugation. Explants of Reuber H-139, Reuber H-35, and Morris 5123 hepatoma cells, grown either in ordinary McCoy's 5a medium or in such medium enriched with iron (0.002% Fe), gave positive immunofluorescence for subunits as well as ferritin. Exposure of a clonal strain of Morris 5123 hepatoma cells to iron-enriched culture medium for varying lengths of time of up to 24 hours resulted in progressive increase in the quantity of ferritin-specific immunofluorescent cytoplasmic material, which was at first present diffusely, and later in clumps. By contrast, during the initial 24-hour period, subunit-specific immunofluorescence remained at relatively low intensity, with diffuse distribution through the cytoplasma. Our findings indicate a) the presence, in the cytoplasm, of the three kinds of hepatoma cells, of unassembled or only partly assembled subunits of fragments of subunits as well as of ferritin, and b) rapid assembly of the protein subunits into apoferritin and ferritin after administration of iron, so that the concentration of subunits in the cytoplasm was not significantly increased.

Animals↗
PubMed1977

Conditionally lethal ribosomal protein mutants: characterization of a locus required for modification of 50S subunit proteins.

Mutagenized P1 bacteriophage were used to transduce a marker (aroE) adjacent to the cluster or ribosomal protein genes located at 72 min on the Escherichia coli chromosome. Linked temperature-sensitive transductants were isolated and characterized. A mutant unable to grow at 44 degrees was found to be defective in protein synthesis both in vivo and in vitro. At the restrictive temperature mutant cells lost all polyribosomes. Analysis of the ribosomal proteins revealed alterations in at least four 50S subunit proteins. The mutation (called rimE1, ribosomal protein modification) mapped between rpsE and aroE. It is suggested that the rimE locus is the structural gene for an activity that modifies a selected number of ribosomal proteins.

Coliphages↗
PubMed1979

Phosphorylation of subunit proteins of intermediate filaments from chicken muscle and nonmuscle cells.

The phosphorylation of the subunit proteins of intermediate (10-nm) filaments has been investigated in chicken muscle and nonmuscle cells by using a two-dimensional gel electrophoresis system. Desmin, the 50,000-dalton subunit protein of the intermediate filaments of muscle, had previously been shown to exist as two major isoelectric variants-alpha and beta-in smooth, skeletal, and cardiac chicken muscle. Incubation of skeletal and smooth muscle tissue with (32)PO(4) (3-) reveals that the acidic variant, alpha-desmin, and three other desmin variants are phosphorylated in vivo and in vitro. Under the same conditions, minor components of alpha- and beta-tropomyosin from skeletal muscle, but not smooth muscle, are also phosphorylated. Both the phosphorylated desmin variants and the nonphosphorylated beta-desmin variant remain insoluble under conditions that solubilize actin and myosin filaments, but leave Z-discs and intermediate filaments insoluble. Primary cultures of embryonic chicken muscle labeled with (32)PO(4) (3-) possess, in addition to the desmin variants described above, a major nonphosphorylated and multiple phosphorylated variants of the 52,000-dalton, fibroblast-type intermediate filament protein (IFP). Filamentous cytoskeletons, prepared from primary myogenic cultures by Triton X-100 extraction, contain actin and all of the phosphorylated and nonphosphorylated variants of both desmin and the IFP. Similarly, these proteins are the major components of the caps of aggregated 10-nm filaments isolated from the same cell cultures previously exposed to Colcemid. These results demonstrate that a nonphosphorylated and several phosphorylated variants of desmin and IFP are present in assembled structures in muscle and nonmuscle cells.

Animals↗
PubMed1977

Biosynthesis of ferritin in rat hepatoma cells and rat livers. I. Synthesis and assembly of protein subunits of ferritin.

Cell fractions were prepared from ACI rat livers and from rat hepatoma cell clone M-5123-C1. Radioimmunoassays of ferritin and of its protein subunits in various cell fractions after biosynthetic labeling with [14C]leucine were done by means of ferritin-specific and subunit-specific rabbit antibody. In both ACI rat livers and M-5123-C1 hepatoma cells free polyribosomes synthesized approximately 81% of the protein subunits of ferritin, and membrane-bound polyribosomes synthesized the rest. In both polyribosomal fractions, [14C]leucine-labeled subunits were detected earlier than [14C]leucine-labeled ferritin and apoferritin (5 min as against 30 min after initiation of a pulse). Time sequence studies of the shifts of biosynthetically labeled subunits and ferritin through different cell compartments provided evidence for vectorial transport of subunits and of ferritin, the direction of transport being from the two polyribosomal systems to the smooth membrane compartment and to the cytosol.

Animals↗
PubMed1978

Immunological studies on cytochrome c oxidase: arrangements of protein subunits in the solubilized and membrane-bound enzyme.

Seven protein subunits of cytochrome c oxidase from bovine heart were isolated by gel filtration in the presence of sodium dodecyl sulphate (subunits I, II and III) and guanidine hydrochloride (subunits V, VI and VII), and ion-exchange chromatography in 6 M urea (subunit IV) after the enzyme had been dissociated in 6 M guanidine hydrochloride. When analysed by highly cross-linked sodium dodecyl sulphate/polyacrylamide gel electrophoresis in the presence of urea, the apparent molecular weights were = I, 36700; II, 24300; III, 20400; IV, 17300; V, 12300; VI, 8700: and VII, 5100. Monospecific rabbit antisera were obtained against subunits I, IV, V, VI and VII and a mixture of subunits II and III. These subunit-specific antisera with the exception of anti-I serum all cross-reacted with the detergent-solubilized native oxidase. Enzymatic studies on purified oxidase indicated that immunoglobulins against subunits II + III, IV, V, VI and VII respectively caused 25, 65, 20, 30 and 25% inhibition while anti-I immunoglobulin did not inhibit the activity. The subunit-specific antisera were used to examine the arrangements of the subunits in the membrane. Enzymatic studies using bovine heart mitochondria and rat liver mitochondrial digitonin particles showed that anti-(II + III) serum, anti-V serum and anti-VII serum all inhibited the oxidase activity while the other antisera did not. On the other hand, results of using 125I-labelled immunoglobulins showed that anti-IV, anti-V and anti-VII sera were bound to the surface of inverted vesicles (matrix side) while all other antisera were not. These results indicate that cytochrome oxidase subunits II and III are situated on the outer surface, and subunit IV is exclusively on the matrix surface while subunits V and VII are exposed on both surfaces of the mitochondrial membrane. Subunits I and VI are buried within the membrane, not exposed on either side.

Animals↗
PubMed1977

Isolation of eukaryotic ribosomal proteins. Purification and characterization of 60 S ribosomal subunit proteins L3, L6, L7', L8, L10, L15, L17, L18, L19, L23', L25, L27', L28, L29, L31, L32, L34, L35, L36, L36', and L37'.

The proteins of the large subunit of rat liver ribosomes were separated into seven groups by stepwise elution from carboxymethylcellulose with LiCl at pH 6.5. Twenty-one proteins (L3, L6, L7', L8, L10, L15, L17, L18, L19, L23', L25, L27', L28, L29, L31, L32, L34, L35, L36, L36', and L37') were isolated from three groups (C60, E60, and F60) by ion exchange chromatography on carboxymethycellulose and by filtration through Sephadex. The amount of protein obtained varied from 0.3 to 25 mg. Nine of the proteins (L6, L8, L18, L27', L28, L29, L34, L36, and L36') had no detectable contamination: the impurities in the others were no greater than 9%. The molecular weight of the proteins was estimated by polyacrylamide gel electrophoresis in sodium dodecyl sulfate; the amino acid composition was determined.

Amino Acids↗
PubMed1976

Isolation of eukaryotic ribosomal proteins. Purification and characterization of the 60 S ribosomal subunit proteins L4, L5, L7, L9, L11, L12, L13, L21, L22, L23, L26, L27, L30, L33, L35', L37, and L39.

The proteins of the large subunit of rat liver ribosomes were separated into seven groups by stepwise elution from carboxymethylcellulose with LiCl at pH 6.5. Seventeen proteins (L4, L5, L7, L9, L11, L12, L13, L21, L22, L23, L26, L27, L30, L33, L35', L37, and L39) were isolated from three of the groups (B60, D60, G60) by ion exchange chromatography on carboxymethylcellulose and by filtration through Sephadex. The amount of protein obtained varied from 0.5 to 15 mg. Eight of the proteins (L9, L11, L13, L21, L22, L35', L37 and L39) had no detectable contamination; the impurities in the others were no greater than 9%. The molecular weight of the proteins was estimated by polyacrylamide gel electrophoresis in sodium dodecyl sulfate; the amino acid composition was determined.

Amino Acids↗
PubMed1978

Isolation of eukaryotic ribosomal proteins. Purification and characterization of the 60 S ribosomal subunit proteins La, Lb, Lf, P1, P2, L13', L14, L18', L20, and L38.

The proteins of the large subunit of rat liver ribosomes were separated into seven groups by stepwise elution from carboxymethylcellulose with LiCl at pH 6.5. Ten proteins (La, Lb, Lf, P1, P2, L13', L14, L18', L20, and L38) were isolated from three groups (A60, B60, and D60) by ion exchange chromatography on carboxymethylcellulose and DEAE-cellulose, and by filtration through Sephadex. The amount of protein obtained varied from 0.3 to 3.8 mg. Two of the proteins (La and L18') had no detectable contamination; the impurities in the others were not greater than 8%. The molecular weight of the proteins was estimated by polyacrylamide gel electrophoresis in sodium dodecyl sulfate; the amino acid composition was determined. Several additional acidic proteins were identified: P1a and P1b are phosphorylated derivatives of P1; P2a, P2b, and P2c are phosphorylated derivatives of P2. P1 and P2 are distinct proteins but both have large amounts of alanine (20.4 and 17.5 mol %).

Amino Acids↗
PubMed1977

Isolation of eukaryotic ribosomal proteins. Purification and characterization of the 40 S ribosomal subunit proteins Sa, Sc, S3a, S3b, S5', S9, S10, S11, S12, S14, S15, S15', S16, S17, S18, S19, S20, S21, S26, S27', and S29.

The proteins of the small subunit of rat liver ribosomes were separated into five main groups by stepwise elution from carboxymethylcellulose with LiCl at pH 6.5. Twenty-one proteins (Sa, Sc, S3a, S3b, S5', S9, S10, S11, S12, S14, S15, S15', S16, S17, S18, S19, S20, S21, S26, S27', and S29) were isolated from three groups (A40, C40, and D40) by ion exchange chromatography on DEAE-cellulose, carboxymethylcellulose, and phosphocellulose and by filtration through Sephadex. The amount of protein obtained varied from 0.1 to 11 mg. Six of the proteins (S5', S10, S11, S18, S19, and S27') had no detectable contamination; the impurities in the others were no greater than 9%. The molecular weight of the proteins was estimated by polyacrylamide gel electrophoresis in sodium dodecyl sulfate; the amino acid composition was determined.

Amino Acids↗
PubMed1976

The isolation of eukaryotic ribosomal proteins. The purification and characterization of the 40 S ribosomal subunit proteins S2, S3, S4, S5, S6, S7, S8, S9, S13, S23/S24, S27, and S28.

The proteins of the small subunit of rat liver ribosomes were separated into five groups by stepwise elution from carboxymethylcellulose with LiCl at pH 6.5 (Collatz, E., Lin, A., Stöffler, G., Tsurugi, K., and Wool, I.G., (1976) J. Biol. Chem. 251, 1808-1816). From the several groups, 12 proteins (S2,S3, S4, S5, S6, S7, S8, S9, S13, S23/S24, S27, and S28) wereisolated by ion exchange chromatography on carboxymethylcellulose, by chromatography on sulfopropyl-Sephadex, and by gel filtration through Sephadex G-75. The amount of protein obtained varied from 1 to 9 mg depending on the number of steps required for the preparation; several proteins had no detectable contamination and the impurities in the others were no greater than 9%. The molecular weight of the proteins was estimated by polyazrylamide gel electrophoresis in sodium dodecyl sulfate; the amino acid composition was determined.

Amino Acids↗
PubMed1976

The ribosomes of Drosophila. IV. Electrophoretic identify among ribosomal subunit proteins from wild type and mutant D. melanogaster and D. simulans.

One- and two-dimensional gel electrophoresis was employed to characterize and compare ribosomal subunit proteins from wild-type D. melanogaster and several mutants, including suppressor-of-forked and four X-linked cold sensitive lethals. The sibling species D. simulans was also studied. We found the electropherogram patterns indistinguishable in all cases.

Animals↗