Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P39060 (endostatin)
 2,284 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Endostatin is a potent angiogenesis inhibitor. The structure of endostatin is unique in that its secondary structure is mainly irregular loops and beta-sheets and contains only a small fraction of alpha-helices with two pairs of disulfide bonds in a nested pattern. We choose human endostatin as a model system to study the folding mechanism of this kind. Nuclear magnetic resonance (NMR), tryptophan emission fluorescence, and circular dichroism (CD) were used to monitor the unfolding process of endostatin upon acid titration. Urea-induced unfolding was used to measure the stability of endostatin under different conditions. Our results show that endostatin is very acid-resistant; some native structure still remains even at pH 2 as evidenced by (1)H NMR. Trifluoroethanol (TFE) destabilizes native endostatin, while it makes endostatin even more acid-resistant in the low pH region. Stability measurement of endostatin suggests that endostatin is still in native structure at pH 3.5 despite the decreased stability. Acid-induced unfolding of endostatin is reversible, although it requires a long time to reach equilibrium below pH 3. Surprisingly, the alpha-helical content of endostatin is increased when it is unfolded at pH 1.6, and the alpha-helical content of the polypeptide chain of unfolded endostatin increases linearly with TFE concentration in the range of 0-30%. This observation indicates that the polypeptide chain of unfolded endostatin has an intrinsic alpha-helical propensity. Our discoveries may provide clues for refolding endostatin more efficiently. The acid-resistance property of endostatin may have biological significance in that it cannot be easily digested by proteases in an acidic environment such as in a lysosome in the cell.
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PMID:Acid-induced unfolding mechanism of recombinant human endostatin. 1499 92

Endostatin can inhibit the proliferation and migration of endothelial cells. It contains two pairs of disulfide bonds in a nested pattern. We constructed three mutants, C33A/C173A, C135A/C165A, and all-Ala, to evaluate the contributions of individual disulfide bonds to the structure, stability, and biological functions of endostatin. Both tryptophan emission fluorescence spectrum and 1H nuclear magnetic resonance spectrum show that C135A/C165A and all-Ala, the two mutants lacking disulfide bond Cys135-Cys165, lost nearly their entire tertiary structure. Although C33A/C173A appears to retain some native-like structures, it is less stable and has a higher helical content, which confirms our earlier hypothesis that the polypeptide backbone of endostatin has a high helical propensity. C135A/C165A and all-Ala mutants lost most of their inhibitory activities both on the migration and proliferation of human microvascular endothelial cells, whereas C33A/C173A is partially active. The mutants without disulfide bond Cys135-Cys165 can hardly be internalized and localized to cytoskeleton and nucleus in the cell, which probably contributes to their loss of inhibition on the migration and proliferation of endothelial cells. Our studies provide a structural basis for the two disulfide bonds on the biological functions of endostatin.
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PMID:Contributions of disulfide bonds in a nested pattern to the structure, stability, and biological functions of endostatin. 1563 76

Bacillus thuringiensis subsp. medellin is known to produce the Cry11Bb protein of 94 kDa, which is toxic for mosquito larvae due to permeabilization of the plasma membrane of midgut epithelial cells. Earlier we found that a 2.8-kDa novel peptide BTM-P1, which was artificially synthesized taking into account the primary structure of Cry11Bb endotoxin, is active against several species of bacteria. In this work we show that BTM-P1 induces cyclosporin A-insensitive swelling of rat liver mitochondria in various salt solutions but not in the sucrose medium. Inorganic phosphate and Ca(2+) significantly increased this effect of the peptide. The uncoupling action of BTM-P1 on oxidative phosphorylation was stronger in the potassium-containing media and correlated with a decrease of the inner membrane potential of mitochondria. In isotonic KNO(3), KCl, or NH(4)NO(3) media, a complete drop of the inner membrane potential was observed at 1-2 microg/ml of the peptide. The peptide-induced swelling was increased by energization of mitochondria in the potassium-containing media, but it was inhibited in the NaNO(3), NH(4)NO(3), and Tris-NO(3) media. All mitochondrial effects of the peptide were completely prevented by adding a single N-terminal tryptophan residue to the peptide sequence. We suggest a mechanism of membrane permeabilization that includes a transmembrane- and surface potential-dependent insertion of the polycation peptide into the lipid bilayer and its oligomerization leading to formation of ion channels and also to the mitochondrial permeability transition pore opening in a cyclosporin A-insensitive manner.
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PMID:Mitochondria permeabilization by a novel polycation peptide BTM-P1. 1571 82

The kinetics of proton transfer in Green Fluorescent Protein (GFP) have been studied as a model system for characterizing the correlation between dynamics and function of proteins in general. The kinetics in EGFP (a variant of GFP) were monitored by using a laser-induced pH jump method. The pH was jumped from 8 to 5 by nanosecond flash photolysis of the "caged proton," o-nitrobenzaldehyde, and subsequent proton transfer was monitored by following the decrease in fluorescence intensity. The modulation of proton transfer kinetics by external perturbants such as viscosity, pH, and subdenaturing concentrations of GdnHCl as well as of salts was studied. The rate of proton transfer was inversely proportional to solvent viscosity, suggesting that the rate-limiting step is the transfer of protons through the protein matrix. The rate is accelerated at lower pH values, and measurements of the fluorescence properties of tryptophan 57 suggest that the enhancement in rate is associated with an enhancement in protein dynamics. The rate of proton transfer is nearly independent of temperature, unlike the rate of the reverse process. When the stability of the protein was either decreased or increased by the addition of co-solutes, including the salts KCl, KNO(3), and K(2)SO(4), a significant decrease in the rate of proton transfer was observed in all cases. The lack of correlation between the rate of proton transfer and the stability of the protein suggests that the structure is tuned to ensure maximum efficiency of the dynamics that control the proton transfer function of the protein.
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PMID:Protein dynamics control proton transfer from bulk solvent to protein interior: a case study with a green fluorescent protein. 1593 81

Ternary Cu(ii) complexes containing an aromatic diimine (DA = di(2-pyridylmethyl)amine (dpa), 4,4'-disubstituted 2,2'-bipyridine (Y(2)bpy; Y = H (bpy), Me, Cl, N(Et)(2), CONH(2) or COOEt) or 2,2'-bipyrimidine) and an aromatic amino acid (AA = l-phenylalanine (Phe), p-substituted phenylalanine (XPhe; X = NH(2), NO(2), F, Cl or Br), l-tyrosine (Tyr), l-tryptophan (Trp) or l-alanine (Ala)) were characterized by X-ray diffraction, spectroscopic and potentiometric measurements. The structures of [Cu(dpa)(Trp)]ClO(4).2H(2)O and [Cu((CONH(2))(2)bpy)(Phe)]ClO(4).H(2)O in the solid state were revealed to have intramolecular pi-pi interactions between the Cu(ii)-coordinated aromatic ring moiety, Cu(DA) (Mpi), and the side chain aromatic ring of the AA (Lpi). The intensities of Mpi-Lpi interactions were evaluated by the stability constants of the ternary Cu(ii) complexes determined at 25 degrees C and I = 0.1 M (KNO(3)), which revealed that the stability enhancement of the Cu(DA)(AA) systems due to the interactions is in the order (CONH(2))(2)bpy < bpy < Me(2)bpy < (Et(2)N)(2)bpy with respect to DA. The results indicate that the electron density of coordinated aromatic diimines influences the intensities of the stacking interactions in the Cu(DA)(AA) systems. The Mpi-Lpi interactions are also influenced by the substituents, X, of Lpi and are in linear relationship with their Hammett sigma(p) values with the exception of X = Cl and Br.
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PMID:Pi-pi stacking assisted binding of aromatic amino acids by copper(II)-aromatic diimine complexes. Effects of ring substituents on ternary complex stability. 1720 Jul 49

Endostatin, a potent angiogenesis inhibitor, is an acid resistant protein with compact tertiary structure. Nuclear magnetic resonance, circular dichroism, and tryptophan emission fluorescence were used to monitor the structural changes of endostatin during acid-, heat-, and urea-induced unfolding processes. Results show that sulfate anions sensitize endostatin to acid, but specifically stabilize it against heat or urea. Moreover, the disappearance of the tertiary structure and the formation of the folding intermediate of endostatin at pH 3.0 are sulfate concentration dependent. These phenomena indicate that sulfate anions stabilize the folding intermediate more than the native structure of endostatin. In addition, heparin shows stronger effect than sodium sulfate on sensitizing endostatin against acid, and very limited stabilizing effect against urea. The loose structure of endostatin upon heparin binding may imply that the physiologically favorable structure for endostatin exerting its biological functions is not as compact as what was reported.
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PMID:Sulfate stabilizes the folding intermediate more than the native structure of endostatin. 1818 53