Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UNIPROT:Q07644 (polypeptide)
 72,197 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The second component of human complement (C2) was purified by a combination of euglobulin precipitation, ion-exchange chromatography, (NH4)2SO4 precipitation and affinity chromatography. The final product was homogeneous by the criterion of polyacrylamide-gel electrophoresis and represents a purification of about 4000-fold from serum with 15-20% yield. Component C2 comprises a single carbohydrate-containing polypeptide chain, with an apparent mol.wt. of 102000; alanine is the N-terminal amino acid. The molecule is rapidly cleaved by activated subcomponent C1s with the loss of haemolytic activity to yield two fragments with apparent mol.wts. of 74000 and 34000. These fragments are not linked by disulphide bonds and can be easily separated. A second protein isolated during the purification of component C2 was identified by its haemolytic and antigenic properties as complement Factor B, the protein serving an analogous function to component C2 in the alternative pathway. The protein, which is also a single carbohydrate-containing polypeptide chain, has an apparent mol.wt. of 95000 and threonine as N-terminal amino acid. The amino acid analyses of component C2 and Factor B are compared.
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PMID:The purification and properties of the second component of human complement. 41 28

Saccharopine dehydrogenase (N6-(glutar-2-yl)-L-ly-sine:NAD oxidoreductase (L-lysine-forming)) from baker's yeast was purified to homogenicity. The overall purification was about 1,200-fold over the crude extract with a yield of about 24%. The purified enzyme had a sedimentation coefficient (S20,w) of 3.0 S. The molecular weight determinations by sedimentation equilibrium, Sephadex G-100 gel filtration, and sodium dodecyl sulfate-polyacrylamide gel electrophoresis gave a value of about 39,000 and, therefore, saccharopine dehydrogenase is a single polypeptide chain enzyme. A Stokes radius of 27 A and a diffusion constant of 7.9 X 10(-7) cm2 s-1 were obtained from Sephadex gel filtration chromatography. The enzyme had a high isoelectric pH of 10.1. The NH2-terminal sequence was Ala-Ala----. The enzyme possessed 3 cysteine residues/molecule; no disulfide bond was present. Incubation of saccharopine dehydrogenase with p-chloromercuribenzoate or iodoacetate resulted in complete loss of enzyme activity. Whereas the coenzyme and substrates were ineffective in protecting from inactivation by p-chloromercuribenzoate, iodoacetate inhibition was protected by excess coenzyme.
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PMID:Purification and characterization of saccharopine dehydrogenase from baker's yeast. 41 69

Macromomycin (MCR), a polypeptide antibiotic previously shown to have antitumor activity in experimental tumors, has been purified into an electrophoretically homogeneous component with an approximate molecular weight of 12,500. MCR has alanine as an NH2-terminal amino acid, 4 cysteine residues, and no arginine or methionine residues. With a fluorescence assay and agarose gel electrophoresis, MCR was shown to induce strand breaks in PM2 DNA in vitro. 2-Mercaptoethanol inhibited the DNA cleavage activity of MCR. When incubated with Novikoff hepatoma ascites cells in tissue culture, MCR caused Novikoff hepatoma ascites cell DNA degradation as observed by the slower sedimentation of DNA on alkaline sucrose density gradient centrifugation when compared to untreated cell DNA. DNA synthesis in Novikoff hepatoma ascites cells was inhibited by 80% after a two-hr treatment with MCR (0.03 microgram/ml). RNA and protein syntheses were inhibited by 25 and less than 10%, respectively, at this concentration of drug. At a concentration of MCR (1.0 microgram/ml), syntheses of DNA and RNA in Novikoff hepatoma ascites cells were totally inhibited. The results of this study suggest that MCR may inhibit tumor cell growth by causing DNA breakage with subsequent inhibition of DNA and other macromolecule syntheses.
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PMID:Purification and mechanism of action of macromomycin. 42 Dec 1

In a survey for abnormal haemoglobin variants in voluntary blood donors in Iran, a new variant was found in a young male who presented no clinical symptoms. It had the same electrophoretic mobility as haemoglobin D in alkaline buffers. Separation of the constituent polypeptide chains in acid urea buffer revealed it to be different from haemoglobin D previously found among Iranians. Analysis of its structure demonstrated a substitution to alanine (beta 47 Asp replaced by Ala) in the same residue as involved in haemoglobin G-Copenhagen (beta 47 Asp replaced by Asn).
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PMID:Haemoglobin Avicenna (beta 47 (CD6) Asp replaced by Ala). A new abnormal haemoglobin. 42 3

Block poly(Ala)16-poly(Lys)13.5 was synthesized by the Leuchs anhydride method. This polypeptide is water soluble in a largely monomeric form, but binds rapidly and spontaneously to unilamellar vesicles of dimyristoyl phosphatidylcholine at pH 7.4. The interaction is evidently of a hydrophobic nature since the complex is not disrupted by salt and no similar reaction is given by polylysine. Evidence for the interaction was obtained by ultrafiltration, chromatography on Sepharose 4B, and sedimentation velocity ultracentrifugation. While direct information on the molecular structure of the complex is still lacking, we propose that this amphipathic block copolymer binds to lipids in a similar manner as intrinsic membrane proteins and hence can be used to study the interactions of intrinsic proteins with lipids.
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PMID:Block poly(Ala)-poly(Lys). A water-soluble model for intrinsic membrane proteins? 49 85

The toxicity of lectins from castor bean (Ricinus communis L.), ricin-D, ricin-E, and castor bean hemagglutinin, was investigated on five cultured cell lines. The differential effect of their constituent polypeptide chains was also investigated using these cell lines. Ricin-D, ricin-E, and castor bean hemagglutinin (CBH) possessed cytoagglutinating activity and cytotoxic activity to all five cell lines. These lectins showed the strongest toxicity to L5178Y cells, which are leukemic cells. The toxic activity of ricin-D was stronger than that of CBH in all cell lines. The constituent polypebtide chains of ricin-D and CBH were separated by DEAE-cellulose chromatography and designated as isoleucine chain and alanine chain denoted by their N-terminal amino acids. Only alanine chain of ricin-D was toxic to cells grown in vitro, whereas isoleucine chain of ricin-D and alanine chain of CBH were not toxic to the cells. Moreover, it was found that both lectins caused syncytium formation in NIH3T3 cells infected with Moloney leukemia virus and this cell fusion activity was shown to be exclusively associated with the alanine chain. Cytotoxic, cell agglutinating, and syncytium forming effect of the lectins is due to binding of the alanine chain of ricin-D to galactose-like residues of the membrane constituents of these cells.
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PMID:Cytotoxic, cell agglutinating, and syncytium forming effect of purified lectins from Ricinus communis on cultured cells. 52 Jul 50

With the use of an enzymatic replacement method, 90%-enriched [1-13C]lysine was introduced into the reactive site of the basic pancreatic trypsin inhibitor. Characterization of the labelled inhibitor with 13C nuclear magnetic resonance (NMR), 1H NMR and chemical methods showed that while the reactive-site peptide bond Lys-15--Ala-16 was properly resynthesized, the polypeptide chain was cleaved at the peptide bond Arg-39--Ala-40 and Arg-39 was removed. Detailed 1H NMR studies showed further that, with the exception of the immediate environment of the modification site, the average spatial structure of the native inhibitor was preserved in the modified protein. Compared to the native inhibitor, the thermal stability of the globular conformation was found to be reduced, interior amide protons exchanged at a faster rate and the internal mobility of aromatic rings located outside the immediate environment of the cleaved peptide bond was essentially unchanged. These observations coincide closely with previous reports on different modifications of the inhibitor and can be explained by a recently proposed dynamic multi-state model for globular proteins. Since the fundamental structural properties of the native inhibitor and full inhibitory activity are preserved after resynthesis, the [1-13C]lys-15-labelled inhibitor with the peptide bond Arg-39--Ala-40 cleaved and Arg-39 removed should be suitable for 13C NMR studies of mechanistic aspects of proteinase-inhibitor interactions.
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PMID:Structural characterization by nuclear magnetic resonance of a reactive-site 13carbon-labelled basic pancreatic trypsin inhibitor with the peptide bond Arg-39--Ala-40 cleaved and Arg-39 removed. 52 93

The molecular mechanism of helix nucleation in peptides and proteins is not yet understood and the question of whether sharp turns in the polypeptide backbone serve as nuclei for protein folding has evoked controversy. A recent study of the conformation of a tetrapeptide containing the stereochemically constrained residue alpha-aminoisobutyric acid, both in solution and the solid state, yielded a structure consisting of two consecutive beta-turns, leading to an incipient 3(10) helical conformation. :This led us to speculate that specific tri- and tetrapeptide sequences may indeed provide a helical twist to the amino-terminal segment of helical regions in proteins and provide a nucleation site for further propagation. The transformation from a 3(10) helical structure to an alpha-helix should be facile and requires only small changes in the phi and psi conformational angles and a rearrangement of the hydrogen bonding pattern. If such a mechanism is involved then it should be possible to isolate an incipient 3(10) helical conformation in a tripeptide amide or tetrapeptide sequence, based purely on the driving force derived from short-range interactions. We have synthesised and studied the model peptide pivaloyl-Pro-Pro-Ala-NHMe (compound I) and provide here spectroscopic evidence for a 3(10) helical conformation in compound I.
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PMID:An incipient 3(10) helix in Piv-Pro-Pro-Ala-NHMe as a model for peptide folding. 55 Dec 71

Cross-linking of the unimer of glutamate dehydrogenase from beef liver (consisting of six polypeptide chains each having a molecular weight of 56000) with dimethyladipimidate and subsequent analysis by sodium dodecylsulfate electrophoresis shows predominantly the trimeric species (molecular weight 168000). Treatment with dimethylimidates of other chain length yields significantly less trimeric species indicating that the amino groups being cross-linked are within a distance of about 0.85 nm. Comparison of the molar amount of incorporated [14C]dimethyladipimidate with the number of modified amino groups (determined with trinitrobenzenesulfonic acid) shows that although 8-9 of the 34 amino groups have reacted, only 2-3 of them are involved in cross-links. Reaction with dimethylimidates inactivates the enzyme. The loss of the activity is partly concomitant to cross-linking to the trimeric species and not simply due to the modification of essential lysine residues. This is supported by the fact that, although more lysine residues react with mono-functional methylimidates, the loss of activity is reduced. Purified chymotryptic and tryptic peptides of the radioactive-labeled trimeric species were subjected to sequence analysis. Six peptides containing 75% of the total label were identified: one involves the amino-terminal residue alanine-1 and the others involve lysine-105, lysine-154, lysine-269, lysine-358 and lysine-399. Quantitative analysis of the specific radioactivity of each peptide/mol lysine leads to the conclusion that only lysine-105, lysine-154, lysine-269 and lysine-358 participate in cross-links, lysine-269 and lysine-358, respectively, being at isologous and lysine-105 cross-linked with lysine-154 at heterologous contact domains of the enzyme. A model for the planar arrangement of the trimeric species in the quaternary structure of glutamate dehydrogenase is discussed. It includes both isologous and heterologous contact areas between the polypeptide chains.
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PMID:Studies of glutamate dehydrogenase. Analysis of quaternary structure and contact areas between the polypeptide chains. 55 96

Complexes of DNA with polypeptides composed of Lys, Ala, and Gly in both a sequential order, poly(L-lysine-L-alanine-glycine), and a statistical distribution, poly(L-lysine36-L-alanine28-glycine), were prepared using gradient dialysis. These polypeptide-DNA complexes were studied using ultraviolet absorption (UV) and circular dichroism (CD) to probe the conformation, binding, and melting behavior of DNA in the complex. Complexes with the sequential polypeptide showed no structural change in the DNA; however, the complexes with the random polypeptide yield CD spectra similar to phi DNA [Maniatis, T., Venable, Jr., J.S., and Lerman, L.S. (1974), J. Mol. Biol. 84, 37]. A second sequential polypeptide, poly(L-Lys-L-Ala-L-Pro)n, -DNA complex was also studied. It was found to exhibit pronounced structural changes as a function of ionic strength and poly-peptide-DNA ratio, more similar to the random sequence that the ordered sequence of the Lys, Ala, Gly polymer. Thus the importance of the composition and amino acid sequence in polypeptides which bind to DNA, even in such simple systems, is demonstrated. Evidence from thermal denaturation, employing simultaneous monitoring of CD and UV changes, supports a model in which specific polypeptides cause condensation of the DNA in the complex into an asymmetric tertiary structure. The relevance of these model systems to chromatin is discussed.
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PMID:Interaction of DNA with poly(L-Lys-L-Ala-Gly) and poly(L-Lys-L-Ala-L-Pro). Circular dichroism and thermal denaturation studies. 55 95


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