Showing papers on "Gel electrophoresis published in 1981"
TL;DR: Gel electrophoresis in studies of equilibrium binding, site distribution, and kinetics of protein-DNA interactions found that binding to the so-called third operator site (03) is 15-18 fold weaker than operator binding, and that the binding reactions with the first and third operators are uncoupled, implying that there is no communication between the sites.
Abstract: We describe the use of gel electrophoresis in studies of equilibrium binding, site distribution, and kinetics of protein-DNA interactions. The method, which we call protein distribution analysis, is simple, sensitive and yields thermodynamically rigorous results. It is particularly well suited to studies of simultaneous binding of several proteins to a single nucleic acid. In studies of the lac repressor-operator interaction, we found that binding to the so-called third operator site (03) is 15-18 fold weaker than operator binding, and that the binding reactions with the first and third operators are uncoupled, implying that there is no communication between the sites. Pseudo-first order dissociation kinetics of the repressor-203 bp operator complex were found to be temperature sensitive, with delta E of 80 kcal mol-1 above 29 degrees C and 26 kcal mol-1 below. The half life of the complex (5 min at 21 degrees C) is shorter than that reported for very high molecular weight operator-containing DNAs, but longer than values reported for much shorter fragments. The binding of lac repressor core to DNA could not be detected by this technique: the maximum binding constant consistent with this finding is 10(5) M-1.
2,394 citations
TL;DR: It is demonstrated that even when pre-formed in the presence of CAP-cAMP, the polymerase-promoter open complex becomes unstable if CAP is then selectively removed, and this gel method is applied to the study of the E. coli lactose operon regulatory system.
Abstract: The use of gel electrophoresis for quantitative studies of DNA-protein interactions is described. This rapid and simple technique involves separation of free DNA from DNA-protein complexes based on differences in their electrophoretic mobilities in polyacrylamide gels. Under favorable conditions both unbound DNA and DNA associated with protein can be quantified. This gel method is applied to the study of the E. coli lactose operon regulatory system. At ionic strengths in the physiological range, the catabolite activator protein (CAP) is shown to form a long-lived complex with the wild type lac promotor, but not with a CAP-insensitive mutant. Formation of a stable "open" or "melted-in" complex of RNA polymerase with the wild type promoter requires the participation of CAP and cyclic AMP. Further, it is demonstrated that even when pre-formed in the presence of CAP-cAMP, the polymerase-promoter open complex becomes unstable if CAP is then selectively removed.
1,759 citations
Book•
01 Jan 1981
TL;DR: Health warning Abbreviations An introduction to polyacylamide gel electrophoresis Gel isotachophoresis Analytical and preparative gel electrofocusing Two-dimensional gel electphoresis Peptide mapping by limited proteolysis using SDS-polyacrylamide Gel electrophoreis Immunoelectrophoresism.
Abstract: Health warning Abbreviations An introduction to polyacylamide gel electrophoresis Gel isotachophoresis Analytical and preparative gel electrofocusing Two-dimensional gel electrophoresis Peptide mapping by limited proteolysis using SDS-polyacrylamide gel electrophoresis Immunoelectrophoresis Appendix 1: Bibliography of polypeptide detection methods Appendix 2: Reagents for the isotopic labelling of proteins Appendix 3: Molecular weights and isoelectric points of selected marker proteins Appendix 4: Suppliers of specialist items for electrophoresis
1,148 citations
TL;DR: The 39,500-dalton major outer membrane protein is a serogroup antigen of C. trachomatis organisms and its extraction resulted in a concomitant loss of the COMC membrane structure and morphology.
Abstract: Elementary bodies (EB) of Chlamydia trachomatis serotypes C, E, and L2 were extrinsically radioiodinated, and whole-cell lysates of these serotypes were compared by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). Autoradiography of the polypeptide profiles identified a major surface protein with an apparent subunit molecular weight of 39,500 that was common to each C. trachomatis serotype. The abilities of nonionic (Triton X-100), dipolar ionic (Zwittergent TM-314), mild (sodium deoxycholate and sodium N-lauroyl sarcosine), and strongly anionic (SDS) detergents to extract this protein from intact EB of the L2 serotype were investigated by SDS-PAGE analysis of the soluble and insoluble fractions obtained after each detergent treatment. Only SDS readily extracted this protein from intact EB. Sarkosyl treatment selectively solubilized the majority of other EB proteins, leaving the 39,500-dalton protein associated with the Sarkosyl-insoluble fraction. Ultrastructural studies of the Sarkosyl-insoluble EB pellet showed it to consist of empty EB particles possessing an apparently intact outer membrane. No structural evidence for a peptidoglycan-like cell wall was found. Morphologically these chlamydial outer membrane complexes (COMC) resembled intact chlamydial EB outer membranes. The 39,500-dalton outer membrane protein was quantitatively extracted from COMC by treating them with 2% SDS at 60 degrees C. This protein accounted for 61% of the total COMC-associated protein, and its extraction resulted in a concomitant loss of the COMC membrane structure and morphology. The soluble extract obtained from SDS-treated COMC was adsorbed to a hydroxylapatite column and eluted with a linear sodium phosphate gradient. The 39,500-dalton protein was eluted from the column as a single peak at a phosphate concentration of approximately 0.3 M. The eluted protein was nearly homogeneous by SDS-PAGE and appeared free of contaminating carbohydrate, glycolipid, and nucleic acid. Hyperimmune mouse antiserum prepared against the 39,500-dalton protein from serotype L2 reacted with C. trachomatis serotypes Ba, E, D, K, L1, L2, and L3 by indirect immunofluorescence with EB but failed to react with serotypes A, B, C, F, G, H, I, and J, with the C. trachomatis mouse pneumonitis strain, or with the C. psittaci feline pneumonitis, guinea pig inclusion conjunctivitis, or 6BC strains. Thus, the 39,500-dalton major outer membrane protein is a serogroup antigen of C. trachomatis organisms.
1,075 citations
TL;DR: The method is useful for the recovery of biologically active DNA from both agarose and high-percentage polyacrylamide gels, thereby enabling purification of DNA fragments up to 20 kb in size with a yield of 60–80%.
806 citations
TL;DR: The procedure should prove useful not only for generation of deglycosylated proteins, but also for assessment of the number of asparagine-linked saccharide chains in a glycoprotein.
800 citations
TL;DR: The sensitivity of the silver stain process is superior to Coomassie Blue and is comparable to autoradiography after in corporation of conventional levels of 35S‐ methionine.
Abstract: A color development system for staining polypeptides in one- and two-dimensional polyacrylamide gel electrophoresis is described. The basis of the Process involves the complexing of silver with polypeptides reactive centers. The reaction is initiated by placing a polypeptide-containing gel, previously equilibrated with an appropriate concentration of silver nitrate, into a reducing solution that contains sodium hydroxide, sodium borohydride, and formaldehyde. After an appropriate time in the reducing solution, the gel is equilibrated through two changes of an enhancing solution that contains sodium carbonate. The sodium carbonate is necessary for optimal color appear in the polypeptide -silver complexes after several hours in the enhancing solution and are best appreciated while viewing over a fluorescent light box that radiates light at 5000°K. The color of each polypeptide-silver complex is clearly visible above the light background of the stained polyacrylamide gel. Colors of stained polypeptide are blue, green, yellow, and red. Subtle shades of colors also appear and thereby allow easy discrimination of overlapping spots of polypeptides in a two-dimensional gel. To illustrate the method's relative sensitively, a two-dimensional pattern of human fibroblast polypeptides is compared with patterns of a duplicate gel that is stained with Coomassie Blue and developed by autoradiography. The sensitivity of the silver stain process is superior to Coomassie Blue and is comparable to autoradiography after in corporation of conventional levels of 35S- methionine. The utility of the procedure for identifying and characterizing human proteins is illustrated by staining human proteins is illustrated by staining human plasma and platelet polypeptides after two-dimensional gel electrophoresis. The gel electrophoresis color development system consists of steps that are simple, reproducible, and sensitive, and most importantly, which yield colored polypeptide-silver complexes that are reproducible from gel to gel and tissue to tissue.
608 citations
TL;DR: It is concluded that seven proteins found in Rous sarcoma virus-transformed cells are probably substrates of p60 src, although they may be substrates for other tyrosine-specific protein kinases activated by p60src.
Abstract: Rous sarcoma virus encodes a tyrosine-specific protein kinase (p60src) which is necessary for cell transformation. To identify substrates for this kinase, we set out to detect phosphotyrosine-containing proteins in Rous sarcoma virus-transformed chicken embryo cells, making use of the known alkali stability of phosphotyrosine. 32P-labeled phosphoproteins were separated by isoelectric focusing and sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The gels were then incubated in alkali. Using this procedure with normal cells, we detected a total of about 190 alkali-resistant phosphoproteins. In Rous sarcoma virus-transformed cells, five phosphoproteins were found which were not detectable in normal cells. Two of these are probably structural proteins of the virus. The other three transformation-dependent phosphoproteins, and four other phosphoproteins which were elevated by transformation, all contained phosphotyrosine. Increased phosphorylation of these proteins did not occur with cells infected with a mutant Rous sarcoma virus, temperature sensitive for transformation, grown at the restrictive temperature. We conclude that these seven proteins are probably substrates of p60src, although they may be substrates for other tyrosine-specific protein kinases activated by p60src.
393 citations
TL;DR: Comparison of the major outer-membrane proteins of H. influenzae type b is a useful technique for investigating the transmission of the organism and may provide a basis for further immunologic characterization of the outer- MEMB proteins.
Abstract: Outer-membrane proteins from isolates of Haemophilus influenzae type b were examined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Sarcosinate-insoluble membrane preparations contained one peptide with a molecular weight of 16,000 and four major peptides with molecular weights of 25,000-40,000. A peptide with a molecular weight of 49,000 (50,000 in some strains) was observed after the samples were heated at 100 C. Fifty-one isolates obtained from patients hospitalized with invasive diseases, primarily meningitis, could be subclassified into nine categories based on reproducible and clearly resolvable differences in the outer-membrane protein profiles. Five categories accounted for 92% of the isolates. Complete concordance was observed in subtypes of strains obtained from epidemiologically related cases and contacts. Thus, comparison of the major outer-membrane proteins of H. influenzae type b is a useful technique for investigating the transmission of the organism and may provide a basis for further immunologic characterization of the outer-membrane proteins.
344 citations
TL;DR: The structure of receptors for insulin-like growth factors in rat liver plasma membranes and the BRL 3A2 rat liver cell line has been examined by chemical cross-linking with disuccinimidyl suberate and sodium dodecyl sulfate-polyacrylamide gel electrophoresis under reducing and nonreducing conditions.
322 citations
TL;DR: Recombinant human leukocyte interferon produced in bacteria (IFLrA) was purified to homogeneity with the use of monoclonal antibodies against leukocytes and Amino acid analysis and the NH2-terminal sequence were consistent with the sequence predicted from the DNA.
TL;DR: To identify the viral core protein that catalyzes the initiation of transcription via the incorporation of a guanosine residue onto primer fragments, irradiated transcription reactions carried out by viral cores in the presence of [alpha-P]GTP as the only ribonucleoside triphosphate with an unlabeled primer RNA suggested that the viral P1 protein catalyzes this incorporation and hence initiates transcription.
Abstract: Purified influenza viral cores catalyze the entire process of viral RNA transcription, which includes the endonucleolytic cleavage of heterologous RNAs containing cap 1 (m(7)GpppNm) structures to generate capped primers 10-13 nucleotides long, the initiation of transcription via the incorporation of a guanosine residue onto the primers, and elongation of the viral mRNAs [Plotch, S. J., Bouloy, M., Ulmanen, L & Krug, R. M. (1980) Cell 23, 847-858]. To identify which viral core protein (nucleocapsid protein, P1, P2, or P3) recognizes the cap 1 structure on the RNA primer, we irradiated (UV) endonuclease reactions carried out by viral cores in the absence of ribonucleoside triphosphates, with a primer RNA labeled in its cap 1 structure with (32)P. The labeled cap was crosslinked to a protein that had a mobility similar to that of the P3 protein, the smaller of the two basic P proteins, in both one- and two-dimensional gel electrophoresis. This strongly suggests that this crosslinked protein is the viral P3 protein. Competition experiments with unlabeled RNAs containing or lacking a cap 1 structure established that this protein recognizes the cap 1 structure on RNAs. This protein remained associated with the cap throughout the transcription reaction, even after the viral mRNA molecules were elongated. To identify the viral core protein that catalyzes the initiation of transcription via the incorporation of a guanosine residue onto primer fragments, we irradiated transcription reactions carried out by viral cores in the presence of [alpha-(32)P]GTP as the only ribonucleoside triphosphate with an unlabeled primer RNA. A labeled guanosine residue was crosslinked to a protein that had a mobility similar to that of the P1 protein, the larger of the two basic P proteins, in both one-and two-dimensional gel electrophoresis. The transcription reaction conditions required to bring this protein in close association with a labeled guanosine residue so that crosslinking could occur indicated that this association most likely occurred coincident with the guanosine residue's being incorporated onto the primer. These results suggest that the viral P1 protein catalyzes this incorporation and hence initiates transcription.
TL;DR: In this article, the authors examined the DNA from brain tissue by endonuclease digestion, separation of the fragments by gel electrophoresis, and hybridization with labeled HSV-1 DNA probes.
Abstract: Herpes simplex virus type 1 (HSV-1) is known to reside latently in the trigeminal ganglia of man. Reactivation of this virus causes skin lesions and may occasionally infect other tissues, including the brain. To determine whether the brain tissue of humans free of clinical signs of HSV-1 infection contains any trace of HSV-1, we examined the DNA from brain tissue by endonuclease digestion, separation of the fragments by gel electrophoresis, and hybridization with labeled HSV-1 DNA probes. Hybrid bands were detected autoradiographically in experiments using cloned and virion-purified fragments of the HSV-1 genome. HSV-1 DNA sequences were found in 6 of 11 human brain DNA samples tested. In some cases, these bands corresponded to the bands expected for the complete viral genome, whereas others contained bands representing only a part of the genome. In some cases, the terminal fragments could be found, suggesting that the DNA was in a linear, nonintegrated form.
TL;DR: Analysis of cross-linked activator protein by sodium dodecyl sulfate-polyacrylamide gel electrophoresis suggested that the protein might be a dimer of identical subunits.
TL;DR: Spleen cells obtained from mice immunized with partially purified human coagulation Factor V were fused with NS-1 mouse myeloma cells, and hybrids were selected and an antibody-positive clone was obtained and passaged as an ascites tumor in mice.
Abstract: Spleen cells obtained from mice immunized with partially purified human coagulation Factor V were fused with NS-1 mouse myeloma cells, and hybrids were selected. Culture media were screened for anti-Factor V activity, and an antibody-positive clone was obtained and passaged as an ascites tumor in mice. The ascitic fluid from the hybridoma-bearing mouse could be diluted 1:10(6) before losing reactivity in an anti-Factor V radioimmunoassay. When immobilized on agarose, the monoclonal antibody quantitatively removed Factor V activity from human plasma. Factor V activity could be eluted with 1.2 M NaCl at pH 6.5. Homogeneous Factor V was isolated by chromatography of barium citrate-adsorbed, polyethylene glycol 6000 precipitated plasma on the antibody column followed by chromatography on phenyl-Sepharose. The isolated Factor V exhibited a single band upon gel electrophoresis in sodium dodecyl sulfate with an apparent Mr comparable to that of bovine Factor V (330,000). Upon exposure to thrombin, the activity of Factor V increased 53-fold when measured in Factor V-deficient plasma. This increased activity was associated with discrete proteolytic cleavages of the parent molecule.
TL;DR: The results suggest that the alpha and beta polypeptides contain both the STX binding site and the scorpion toxin binding site of the mammalian sodium channel.
Abstract: The saxitoxin (STX) receptor has been purified 740-fold from rat brain by a combination of ion exchange chromatography, wheat germ agglutinin chromatography, and sedimentation on sucrose gradients to a specific activity of 1488 pmol/mg of protein. The best fractions were estimated to be 47% pure from their specific activity or 66% pure on the basis of NaDodSO4 gel electrophoresis. Two polypeptides, alpha (Mr approximately equal to 270,000 +/- 10,000) and beta (Mr approximately equal to 38,300 +/- 2000) (mean +/- SD) copurify with STX binding activity. Two polypeptides of the same apparent Mr are specifically covalently labeled by photoreactive derivatives of 125I-labeled scorpion toxin in rat brain synaptosomes and are likely to be identical to alpha and beta. The solubilized STX receptor has a Mr of 316,000 +/- 63,000, limiting its composition to one alpha polypeptide and one or more beta polypeptides per soluble receptor. Our results suggest that the alpha and beta polypeptides contain both the STX binding site and the scorpion toxin binding site of the mammalian sodium channel.
TL;DR: A procedure has been developed for the isolation of human Factor VII to apparent homogeneity as judged by the analytical disc electrophoretic system of Davis and by sodium dodecyl sulfate (SDS)-polyacrylamide gel electrophoresis.
TL;DR: The molecular model implicated by these findings is that platelet-derived growth factor consists of two different polypeptides chains, linked by disulphide bridges.
Abstract: Platelet-derived growth factor was purified from fresh platelets by a large-scale procedure not involving the use of SDS (sodium dodecyl sulphate). The product, 0.5 mg of platelet-derived growth factor, obtained from about 3 x 10(13) platelets migrated as a single component in analytical gel electrophoresis in the presence of SDS and showed no inhomogeneity on sedimentation-equilibrium analysis in the ultracentrifuge. It had a high specific activity, 2 ng of platelet-derived growth factor/ml (70pM) being equivalent to 1% (v/v) human serum in an assay for multiplication-stimulating activity. Amino acid analysis revealed that platelet-derived growth factor contains all the common amino acids, except tryptophan, but no hexosamine. The molecular weight of platelet-derived growth factor, as determined by sedimentation-equilibrium analysis, was about 33 000. A similar value was obtained by gel electrophoresis in SDS under non-reducing conditions. In the presence of reducing agents the factor molecule was converted into two distinct components of lower molecular weight (17 000 and 14 000 respectively), as demonstrated by protein staining. The molecular model implicated by these findings is that platelet-derived growth factor consists of two different polypeptides chains, linked by disulphide bridges.
TL;DR: A substantial structural similarity between the human Sm-C and insulin receptors paralleling the homology of the native hormones and their actions is demonstrated.
Abstract: Human placental receptors for insulin and somatomedin C (Sm-C) were affinity labeled with [125I]insulin and [125I]Sm-C by using the bifunctional cross-linking agent disuccinimidyl suberate. Analysis by sodium dodecyl sulfate-polyacrylamide gel electrophoresis demonstrated that both labeled hormones were specifically cross-linked to three protein species with apparent molecular weights of 240 000, 310 000, and 330 000. Following disulfide bond reduction, subunits of approximately 140 000 daltons were evident. Partial reduction of disulfide bonds yielded intermediate-sized species with apparent molecular weights of 180 000, suggesting the existence of an additional, smaller subunit attached to the 140 000-dalton subunit. Limited proteolysis of the hormone-receptor complexes with chymotrypsin, trypsin, and Staphylococcus aureus V-8 protease gave similar but not identical results for each labeled receptor. The distinction between the two receptors was further documented by inhibition of affinity labeling with graded amounts of the native hormones. These data demonstrate a substantial structural similarity between the human Sm-C and insulin receptors paralleling the homology of the native hormones and their actions.
01 Jan 1981
TL;DR: In this paper, a rat brain tryptophan 5-monooxygenase was activated by incubation with ATP, Mg+, calmodulin, and micromolar concentrations of Ca2+.
Abstract: Rat brain tryptophan 5-monooxygenase was activated by incubation with ATP, Mg+, calmodulin, and micromolar concentrations of Ca2+. The activating activity was resolved into two distinct peaks upon gel filtration on Sepharose CL-GB: one, Ca2+-, calmodulindependent protein kinase, and the other, a heat-labile activator protein. The activator protein was purified to apparent homogeneity from rat brain by a procedure involving calmodulin-Sepharose 4B, Sephadex G-150, and phenyl-Sepharose CL-4B column chromatography. The molecular weight of the activator protein was determined to be 70,000 by sedimentation equilibrium and by gel filtration on Sephadex G-150. The protein gave a single band on sodium dodecyl sulfate-polyacrylamide gel electrophoresis, the molecular weight of which was estimated to be 35,000, indicating that the protein might be composed of two identical subunits. Analysis of cross-linked activator protein by sodium dodecyl sulfate-polyacrylamide gel electrophoresis also suggested that the protein might be a dimer of identical subunits. Some other molecular properties of the activator protein were: sedimentation coefficient, 4.3 S; Stokes radius, 3.6 nm; diffusion coefficient, 6.0 X lo-' cm2/s; frictional ratio, 1.32; and partial specific volume, 0.73 cm3/g. The activator protein activated tyrosine 3-monooxygenase as well as tryptophan 5-monooxygenase in the presence of ATP, M&+, Ca2+, calmodulin, and Ca2+-, calmodulin-dependent protein kinase.
TL;DR: The in vitro yeast tubulin assembly is inhibited by the fungicide methyl N-(benzimidazol-2-yl)carbamate, the active component of benomyl, whereas in vitro brain 6S tubulinAssembly is resistant, which suggests that the inhibitory effect of Benomyl on yeast cell division is due to its antimicrotubule action.
Abstract: Tubulin was purified from yeast homogenate by DEAE-Sephadex column chromatography and temperature-dependent assembly. The yeast tubulin subunits comigrate with the brain alpha-tubulin subunit on one-dimensional sodium dodecyl sulfate gel electrophoresis. The in vitro yeast tubulin assembly is inhibited by the fungicide methyl N-(benzimidazol-2-yl)carbamate, the active component of benomyl, whereas in vitro brain 6S tubulin assembly is resistant. This suggests that the inhibitory effect of benomyl on yeast cell division is due to its antimicrotubule action.
TL;DR: The increase in coagulation activity observed upon treatment of human Factor V with thrombin or the Factor V activator from Russell's viper venom seems to correlate with the generation of the doublet Mr = 95,0090-91,000 component.
TL;DR: A method is described to detect DNA polymerases and nucleases in homogeneous or crude enzyme preparations after electrophoresis in SDS-polyacrylamide gels containing the appropriate template or substrate.
Abstract: A method is described to detect DNA polymerases and nucleases in homogeneous or crude enzyme preparations after electrophoresis in SDS-polyacrylamide gels(2) containing the appropriate template or substrate. DNA polymerases are electrophoresed in a gel containing gapped calf thymus DNA and after a renaturation treatment, the gel is incubated in a reaction mixture in which one deoxyribonucleoside triphosphate is [alpha-32P]-labelled. Incorporation of radioactivity into DNA is detected at the vicinity of the polymerase band by autoradiography. An associated nuclease activity can be measured after electrophoresis in a gel containing 32P-labelled gapped DNA, when nucleolytic digestion is seen as a clear band in the resulting autoradiogram. The gels can subsequently be stained with Coomassie blue to establish identical molecular weights of polymerase, nuclease and protein bands. Applications of this technique are discussed.
TL;DR: Bodian's silver method was used to stain polypeptides of rat spinal cord or peripheral nerve separated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis.
Abstract: Bodian's silver method was used to stain polypeptides of rat spinal cord or peripheral nerve separated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The bands corresponding to the t...
TL;DR: Guinea pig antibodies raised against desmosomal proteins as markers specific to this so far only morphologically define class of junctions are proposed to improve identification and classification of intercellular junctions.
TL;DR: A membrane-bound enzyme which degrades substance P (an undecapeptide) has been purified from human brain and the properties of this enzyme suggest that it may be involved in the physiological inactivation of the peptide by neural tissues.
Abstract: A membrane-bound enzyme which degrades substance P (an undecapeptide) has been purified from human brain. The properties of this enzyme suggest that it may be involved in the physiological inactivation of the peptide by neural tissues. Enzyme activity was extracted from a membrane fraction of human diencephalon with a non-ionic detergent, Brij 35, and activity was monitored by measuring the disappearance of added substance P using radioimmunoassay, bioassay or radiochemical assay. The enzyme was purified about 1000-fold by chromatography on DEAE-cellulose, hydroxyapatite and Sephadex gel filtration columns. To identify the cleavage sites in substance P, the peptide was incubated with the purified enzyme and the breakdown products were separated by reverse-phase high-performance liquid chromatography and identified by amino acid analysis. The results suggested that the enzyme preparation was functionally homogeneous and it cleaved substance P between Gln6–Phe7, Phe7–Phe8 and Phe8-Gly9, with no exopeptidase action. The enzyme had a pH optimum in the range 7–9 and was strongly inhibited by metal-chelating agents, but not affected by most other peptidase inhibitors; it can thus be classified as a neutral metallo-endopeptidase. The enzyme was thermolabile and had a molecular weight of 40000–50000 as estimated by gel filtration, density-gradient ultracentrifugation and sodium dodecylsulphate gel electrophoresis. The highly purified substance-P-degrading enzyme could be distinguished from previously described peptidases for which substance P is a substrate. An important feature was that substance P was the preferred substrate among various other neuropeptides tested.
TL;DR: Comparative structural analysis by chymotryptic 125I-peptide mapping was performed on major proteins from the prototype strains as well as from six non-serotypable strains, indicating that the serotype determinants reside within the variable hydrophilic regions of major outer membrane proteins.
Abstract: Group B Neisseria meningitidis is thus far subdivided into 15 protein serotypes based on antigenically different major outer membrane proteins. Most serotypes have three or four major proteins in their outer membranes. Comparative structural analysis by chymotryptic 125I-peptide mapping was performed on these major proteins from the prototype strains as well as from six non-serotypable strains. The major outer membrane proteins from each of the serotypes were first separated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis using the Laemmli system. Individual proteins within the gel slices were radioiodinated and digested with chymotrypsin, and then their 125I-peptides were separated by electrophoresis and chromatography on cellulose thin-layer plates. The peptide maps obtained by autoradiography were categorized into five different structural classes which correlated with the apparent molecular weights of proteins, i.e., 46 +/- 1K, 41 +/- 1K, 38 +/- 1K, 33 +/- 1K, and 28 +/- 1K. Each of the major outer membrane proteins within a strain had a distinctly different chymotryptic peptide map, indicating significant differences in the primary structure of these proteins. In contrast, outer membrane proteins of the same or very similar molecular weight from different serotype strains had similar, occasionally identical peptide maps, indicating a high degree of structural homology. The unique peptides from proteins of the same structural classes were often hydrophilic, whereas common peptides were often hydrophobic, suggesting that the serotype determinants reside within the variable hydrophilic regions of major outer membrane proteins.
TL;DR: A large seasonal variation in polyphenol oxidase activity may result from a decrease in enzyme content rather than inhibition of the enzyme present.
Abstract: Polyphenol oxidase activity (E.C. 1.14.18.1) has been found in two enzyme species isolated from thylakoid membranes of spinach chloroplasts. The proteins were released from the membrane by sonication and purified >900-fold by ammonium sulfate precipitation, gel filtration, and ion-exchange chromatography. The enzymes appear to be the tetramer and monomer of a subunit with a molecular weight of 42,500 as determined by lithium dodecyl sulfate gel electrophoresis. The higher molecular weight enzyme is the predominant form in freshly isolated preparations but on aging or further purification, the amount of lower molecular weight enzyme increases at the expense of the higher.Sonication releases polyphenol oxidase from the membrane largely in the latent state. C(18) fatty acids, especially linolenic acid, are potent activators of the enzymic activity. In the absence of added fatty acids, the isolated enzyme spontaneously, but slowly, activates with time.Purified polyphenol oxidase utilizes o-diphenols as substrates and shows no detectable levels of monophenol or p-diphenol oxidase activities. The K(m) values for 3,4-dihydroxyphenylalanine and O(2) are 6.5 and 0.065 millimolar, respectively. Suitable substrates include chlorogenic acid, catechol, caffeic acid, pyrogallol, and dopamine; however, the enzyme is substrate-inhibited by the last four at concentrations near their K(m) A large seasonal variation in polyphenol oxidase activity may result from a decrease in enzyme content rather than inhibition of the enzyme present.
TL;DR: Immunofluorescent studies with this antiserum and human erythrocytes revealed the presence of an immunologically similar protein on the plasma membrane of these cells suggesting that this protein may function as a folate receptor.
TL;DR: A five-component enzyme system which catalyzes synthesis of acetylphosphate from methyltetrahydrofolate plus pyruvate has been purified from the homoacetate-fermenting bacterium, Clostridium thermoaceticum, and some properties of the phosphotransacetylase are presented.