scholarly journals Formation of complement subcomponent C1q-immunoglobulin G complex. Thermodynamic and chemical-modification studies

1982 ◽  
Vol 205 (2) ◽  
pp. 361-372 ◽  
Author(s):  
E J Emanuel ◽  
A D Brampton ◽  
D R Burton ◽  
R A Dwek
Keyword(s):  
Immunoglobulin G ◽  
Water Soluble ◽  
Small Peptide ◽  
Experimental Conditions ◽  
Salt Ions ◽  
Salt Range ◽  
Lysine Residues ◽  
Arginine Residues ◽  
Equilibrium Process ◽  
Glycine Ethyl Ester

The interaction between the complement subcomponent C1q and immunoglobulin G was investigated under a variety of experimental conditions. Formation of the subcomponent C1q-immunoglobulin G complex was shown to be an equilibrium process. Thermodynamic studies of the effect of varying the ionic strength indicate that over the salt range 0.15-0.225 M-NaCl the binding of subcomponent C1q to immunoglobulin aggregates releases 9-12 salt ions (Na+ and/or Cl-), illustrating the importance of ionic interactions for the formation of the complex. The effects of small peptide and organic ion inhibitors support this conclusion. Chemical modifications of carboxylate residues on immunoglobulin G by glycine ethyl ester/water-soluble carbodi-imide (up to 12 residues modified per whole molecule of immunoglobulin G) and of lysine residues by acetic anhydride (3 residues per whole molecule of immunoglobulin G) or methyl acetimidate (19 residues per whole molecule of immunoglobulin G) lowered the binding affinity of immunoglobulin for subcomponent C1q. Modification of arginine residues by cyclohexane-1,2-dione-1,2 (14 residues per whole molecule of immunoglobulin G) and of tryptophan by hydroxynitrobenzyl bromide (2 residues per whole molecule of immunoglobulin G), however, had little or no effect. The results are consistent with the proposal that the subcomponent-C1q-binding site on immunoglobulin G is to be found on the last two beta-strands of the Cv2 domain [Burton, Boyd, Brampton, Easterbrook-Smith, Emanuel, Novotny, Rademacher, van Schravendijk, Sternberg & Dwek (1980) Nature (London) 288, 338-344].

Review of Progress in Predicting Protein Methylation Sites

2019 ◽  
Vol 23 (15) ◽  
pp. 1663-1670 ◽  
Author(s):  
Chunyan Ao ◽  
Shunshan Jin ◽  
Yuan Lin ◽  
Quan Zou
Keyword(s):  
Gene Expression ◽  
Signal Transduction ◽  
Transcriptional Activity ◽  
Regulation Of Gene Expression ◽  
Protein Methylation ◽  
Biological Processes ◽  
Post Translational Modification ◽  
Regulatory Enzymes ◽  
Lysine Residues ◽  
Arginine Residues

Protein methylation is an important and reversible post-translational modification that regulates many biological processes in cells. It occurs mainly on lysine and arginine residues and involves many important biological processes, including transcriptional activity, signal transduction, and the regulation of gene expression. Protein methylation and its regulatory enzymes are related to a variety of human diseases, so improved identification of methylation sites is useful for designing drugs for a variety of related diseases. In this review, we systematically summarize and analyze the tools used for the prediction of protein methylation sites on arginine and lysine residues over the last decade.

Molecularly Imprinted Sensor for Ascorbic Acid Based on Gold Nanoparticles and Multiwalled Carbon Nanotubes

2020 ◽  
Vol 16 (7) ◽  
pp. 905-913
Author(s):  
Youyuan Peng ◽  
Qingshan Miao
Keyword(s):  
Carbon Nanotubes ◽  
Gold Nanoparticles ◽  
Ascorbic Acid ◽  
Multiwalled Carbon Nanotubes ◽  
Ph Value ◽  
Biological Fluids ◽  
Water Soluble ◽  
Multiwalled Carbon ◽  
Experimental Conditions ◽  
Molecularly Imprinted

Background: L-Ascorbic acid (AA) is a kind of water soluble vitamin, which is mainly present in fruits, vegetables and biological fluids. As a low cost antioxidant and effective scavenger of free radicals, AA may help to prevent diseases such as cancer and Parkinson’s disease. Owing to its role in the biological metabolism, AA has also been utilized for the therapy of mental illness, common cold and for improving the immunity. Therefore, it is very necessary and urgent to develop a simple, rapid and selective strategy for the detection of AA in various samples. Methods: The molecularly imprinted poly(o-phenylenediamine) (PoPD) film was prepared for the analysis of L-ascorbic acid (AA) on gold nanoparticles (AuNPs) - multiwalled carbon nanotubes (MWCNTs) modified glass carbon electrode (GCE) by electropolymerization of o-phenylenediamine (oPD) and AA. Experimental parameters including pH value of running buffer and scan rates were optimized. Scanning electron microscope (SEM), fourier-transform infrared (FTIR) spectra, cyclic voltammetry (CV) and differential pulse voltammetry (DPV) were utilized for the characterization of the imprinted polymer film. Results: Under the selected experimental conditions, the DPV peak currents of AA exhibit two distinct linear responses ranging from 0.01 to 2 μmol L-1 and 2 to 100 μmol L-1 towards the concentrations of AA, and the detection limit was 2 nmol L-1 (S/N=3). Conclusion: The proposed electrochemical sensor possesses excellent selectivity for AA, along with good reproducibility and stability. The results obtained from the analysis of AA in real samples demonstrated the applicability of the proposed sensor to practical analysis.

scholarly journals Arginine residues of the globular regions of human C1q involved in the interaction with immunoglobulin G

1993 ◽  
Vol 268 (14) ◽  
pp. 10393-10402
Author(s):  
G. Marqués ◽  
L.C. Antón ◽  
E. Barrio ◽  
A. Sánchez ◽  
S. Ruiz ◽  
...  
Keyword(s):  
Immunoglobulin G ◽  
Arginine Residues

Kinetics of reactions of acyl isothiocyanates with amines

1980 ◽  
Vol 45 (8) ◽  
pp. 2334-2342 ◽  
Author(s):  
Ján Imrich ◽  
Pavol Kristian ◽  
Dušan Podhradský ◽  
Milan Dzurilla
Keyword(s):  
Solvent Polarity ◽  
Uv Spectra ◽  
Spectroscopic Methods ◽  
Stopped Flow ◽  
Analogous Reaction ◽  
Reaction Products ◽  
Experimental Conditions ◽  
Glycine Ethyl Ester ◽  
Nucleophilic Reagents ◽  
Kinetics Of

The kinetics of reactions of 4-substituted benzoyl, cinnamoyl and phenyl isothiocyanates with aliphatic amines and glycine ethyl ester in organic solvents was studied by the stopped-flow and UV spectroscopic methods. The reaction of acyl isothiocyanates with the nucleophilic reagents employed proved to be 103 - 104 times faster than analogous reaction of phenyl isothiocyanates. A linear correlation between logk and σp constants with positive ρ slope was found. The solvent polarity has only a negligible effect on the reaction. UV spectra as well as gas chromatography of the reaction products proved that under the employed experimental conditions N,N'-disubstituted thioureas are the sole reaction products.

scholarly journals 5-Phenyl-10,15,20-Tris(4-sulfonatophenyl)porphyrin: Synthesis, Catalysis, and Structural Studies

Molecules ◽  
2018 ◽  
Vol 23 (12) ◽  
pp. 3363 ◽  
Author(s):  
Aitor Arlegui ◽  
Zoubir El-Hachemi ◽  
Joaquim Crusats ◽  
Albert Moyano
Keyword(s):  
Alder Reaction ◽  
Water Soluble ◽  
Experimental Conditions ◽  
One Pot ◽  
Force Microscopy ◽  
Diels Alder Reaction ◽  
Transmission Electron ◽  
Porphyrin Synthesis ◽  
The One ◽  
Water Soluble Porphyrin

A convenient protocol for the preparation of 5-phenyl-10,15,20-tris(4-sulfonatophenyl)porphyrin, a water-soluble porphyrin with unique aggregation properties, is described. The procedure relies on the one-pot reductive deamination of 5-(4-aminophenyl)-10,15,20-tris(4-sulfonatophenyl)porphyrin, that can be in turn easily obtained from 5,10,15,20-tetraphenylporphyrin by a known three-step sequence involving mononitration, nitro to amine reduction and sulfonation of the phenyl groups. This method provides the title porphyrin in gram scale, and compares very favorably with the up to now only described procedure based on the partial sulfonation of TPP, that involves a long and tedious chromatographic enrichment of the final compound. This has allowed us to study for the first time both the use of its zwitterionic aggregate as a supramolecular catalyst of the aqueous Diels–Alder reaction, and the morphology of the aggregates obtained under optimized experimental conditions by atomic force microscopy and also by transmission electron cryomicroscopy.

scholarly journals Evading the Proteasome: Absence of Lysine Residues Contributes to Pertussis Toxin Activity by Evasion of Proteasome Degradation

2007 ◽  
Vol 75 (6) ◽  
pp. 2946-2953 ◽  
Author(s):  
Zoë E. V. Worthington ◽  
Nicholas H. Carbonetti
Keyword(s):  
Pertussis Toxin ◽  
Intracellular Transport ◽  
Cellular Activity ◽  
Wild Type ◽  
Proteasome Degradation ◽  
Lysine Residues ◽  
Arginine Residues ◽  
A Subunit ◽  
Adp Ribosyltransferase

ABSTRACT Pertussis toxin (PT) is an important virulence factor produced by Bordetella pertussis. PT holotoxin comprises one enzymatically active A subunit (S1), associated with a pentamer of B subunits. PT is an ADP-ribosyltransferase that modifies several mammalian heterotrimeric G proteins. Some bacterial toxins are believed to undergo retrograde intracellular transport through the Golgi apparatus to the endoplasmic reticulum (ER). The ER-associated degradation (ERAD) pathway involves the removal of misfolded proteins from the ER and degradation upon their return to the cytosol; this pathway may be exploited by PT and other toxins. In the cytosol, ERAD substrates are ubiquitinated at lysine residues, targeting them to the proteasome for degradation. We hypothesize that S1 avoids ubiquitination and proteasome degradation due to its lack of lysine residues. We predicted that the addition of lysine residues would reduce PT toxicity by allowing ubiquitination and degradation to occur. Variant forms of PT were engineered, replacing one, two, or three arginines with lysines in a variety of locations on S1. Several variants were identified with wild-type in vitro enzymatic activity but reduced cellular activity, consistent with our hypothesis. Significant recovery of the cellular activity of these variants was observed when CHO cells were pretreated with a proteasome inhibitor. We concluded that the replacement of arginine residues with lysine in the S1 subunit of PT renders the toxin subject to proteasomal degradation, suggesting that wild-type PT avoids proteasome degradation due to an absence of lysine residues.

scholarly journals Chemical modification studies on a lectin from Saccharomyces cerevisiae (baker's yeast)

1987 ◽  
Vol 244 (3) ◽  
pp. 579-584 ◽  
Author(s):  
M Kundu ◽  
J Basu ◽  
A Ghosh ◽  
P Chakrabarti
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Chemical Modification ◽  
Binding Site ◽  
Structural Changes ◽  
Thiol Groups ◽  
Lectin Activity ◽  
Partial Protection ◽  
Sugar Binding ◽  
Arginine Residues ◽  
Glycine Ethyl Ester

The effect of chemical modification on a galactose-specific lectin isolated from a fatty acid auxotroph of Saccharomyces cerevisiae was investigated in order to identify the type of amino acids involved in its agglutinating activity. Modification of 50 free amino groups with succinic anhydride or citraconic anhydride led to an almost complete loss of activity. This could not be protected by the inhibitory sugar methyl alpha-D-galactopyranoside. Treatment with N-bromosuccinimide and N-acetylimidazole, for the modification of tryptophan and tyrosine residues, did not affect lectin activity. Modification of carboxy groups with glycine ethyl ester greatly affected lectin activity, although sugars afford partial protection. Modification of four thiol groups with N-ethylmaleimide was accompanied by a loss of 85% of the agglutinating activity, and two thiol groups were found to be present at the sugar-binding site of the lectin. Modification of 18 arginine residues with cyclohexane-1,2-dione and 26 histidine residues with ethoxyformic anhydride led to a loss of lectin activity. However, in these cases, modification was not protected by the abovementioned inhibitory sugar, suggesting the absence of these groups at the sugar-binding site. In all the cases, immunodiffusion studies with modified lectin showed no gross structural changes which could disrupt antigenic sites of the lectin.

scholarly journals Arginine residues are critical for the heparin-cofactor activity of antithrombin III

1985 ◽  
Vol 231 (1) ◽  
pp. 59-63 ◽  
Author(s):  
A M Jorgensen ◽  
C L Borders ◽  
W W Fish
Keyword(s):  
Time Course ◽  
Antithrombin Iii ◽  
Rapid Rate ◽  
Rapid Loss ◽  
Inhibitor Molecule ◽  
At Iii ◽  
Lysine Residues ◽  
Arginine Residues ◽  
Cofactor Activity

A dilution/quench technique was used to monitor the time course of chemical modification on the heparin-cofactor (a) and progressive thrombin-inhibitory (b) activities of human antithrombin III. Treatment of antithrombin III (AT III) with 2,4,6-trinitrobenzenesulphonate at pH 8.3 and 25 degrees C leads to the loss of (a) at 60-fold more rapid rate than the loss of (b). This is consistent with previous reports [Rosenberg & Damus (1973) J. Biol. Chem. 248, 6490-6505; Pecon & Blackburn (1984) J. Biol. Chem. 259, 935-938] that lysine residues are involved in the binding of heparin to AT III, but not in thrombin binding. Treatment of AT III with phenylglyoxal at pH 8.3 and 25 degrees C again leads to a more rapid loss of (a) than of (b), with the loss of the former proceeding at a 4-fold faster rate. The presence of heparin during modification with phenylglyoxal significantly decreases the rate of loss of (a). Full loss of (a) correlates with the modification of seven arginine residues per inhibitor molecule, whereas loss of (b) does not commence until approximately four arginine residues are modified and is complete upon the modification of approximately eleven arginine residues per inhibitor molecule. This suggests that (the) arginine residue(s) in AT III are involved in the binding of heparin in addition to the known role of Arg-393 at the thrombin-recognition site [Rosenberg & Damus (1973) J. Biol. Chem. 248, 6490-6505; Jörnvall, Fish & Björk (1979) FEBS Lett. 106, 358-362].

scholarly journals Synthesis, Characterization, and Interaction with Biomolecules of Platinum(II) Complexes with Shikimic Acid-Based Ligands

2013 ◽  
Vol 2013 ◽  
pp. 1-12 ◽  
Author(s):  
Yan Peng ◽  
Min-Min Zhang ◽  
Zhen-Feng Chen ◽  
Kun Hu ◽  
Yan-Cheng Liu ◽  
...  
Keyword(s):  
Shikimic Acid ◽  
Covalent Binding ◽  
Carbon Chain ◽  
Water Soluble ◽  
Cytotoxic Activities ◽  
Experimental Conditions ◽  
H Nmr ◽  
Mtt Method ◽  
Low Cytotoxicity

Starting from the active ingredient shikimic acid (SA) of traditional Chinese medicine and NH2(CH2)nOH, (n=2–6), we have synthesized a series of new water-soluble Pt(II) complexes PtLa–eCl2, where La–eare chelating diamine ligands with carbon chain covalently attached to SA (La–e= SA-NH(CH2)nNHCH2CH2NH2; La,n=2; Lb,n=3; Lc,n=4; Ld,n=5; Le,n=6). The results of the elemental analysis, LC-MS, capillary electrophoresis, and1H,13C NMR indicated that there was only one product (isomer) formed under the present experimental conditions, in which the coordinate mode of PtLa–eCl2was two-amine bidentate. Theirin vitrocytotoxic activities were evaluated by MTT method, where these compounds only exhibited low cytotoxicity towards BEL7404, which should correlate their low lipophilicity. The interactions of the five Pt(II) complexes with DNA were investigated by agarose gel electrophoresis, which suggests that the Pt(II) complexes could induce DNA alteration. We also studied the interactions of the Pt(II) complexes with5′-GMP with ESI-MS and1H NMR and found that PtLbCl2, PtLcCl2, and PtLdCl2could react with5′-GMP to form mono-GMP and bis-GMP adducts. Furthermore, the cell-cycle analysis revealed that PtLbCl2, PtLcCl2cause cell G2-phase arrest after incubation for 72 h. Overall, these water-soluble Pt(II) complexes interact with DNA mainly through covalent binding, which blocks the DNA synthesis and replication and thus induces cytotoxicity that weakens as the length of carbon chain increases.

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