scholarly journals The covalent-binding reaction of complement component C3

1981 ◽  
Vol 193 (1) ◽  
pp. 115-127 ◽  
Author(s):  
R B Sim ◽  
T M Twose ◽  
D S Paterson ◽  
E Sim
Keyword(s):  
Ionic Strength ◽  
Covalent Binding ◽  
Limited Proteolysis ◽  
Life Time ◽  
Reactive Intermediate ◽  
Complement Protein ◽  
Binding Reaction ◽  
Complement Component C3 ◽  
Binding Surface ◽  
Nitrogen Nucleophiles

The complement protein C3, when activated by limited proteolysis, forms a short-lived reactive intermediate fragment, ‘nascent’ C3b, which is known to bind covalently to certain surfaces. The characteristics of the covalent binding reaction have been studied by using Sepharose-trypsin as a combined proteolytic activator and binding surface for C3. Binding of C3 to Sepharose-trypsin is saturable, with a maximum of 25-26 molecules of C3b bound per molecule of trypsin. A minimum life-time of about 60 microseconds for the reactive intermediate has been calculated from binding of C3 at saturation. Initial binding efficiencies of over 30% can be obtained at physiological pH and ionic strength. The efficiency of C3 binding to Sepharose-trypsin decreases as pH increases and also shows a slight decline at high ionic strength. The covalent binding of C3 to Sepharose-trypsin can be inhibited by a range of oxygen and nitrogen nucleophiles. Activation of C3 in the presence of radioactive forms of four such nucleophiles, phenylhydrazine, methylamine, glycerol and glucosamine results in apparent covalent incorporation of the nucleophile into the C3d fragment of C3. The quantity of radioactive nucleophile bound can be predicted from the observed potency of the nucleophile as an inhibitor of the binding of C3 to Sepharose-trypsin. The radioactive nucleophiles may be considered as ‘active-site’ labels for C3.

scholarly journals Effect of thiol compounds on human complement component C4

1993 ◽  
Vol 289 (3) ◽  
pp. 801-805 ◽  
Author(s):  
S Edmonds ◽  
A Gibb ◽  
E Sim
Keyword(s):  
Potent Inhibitor ◽  
Covalent Binding ◽  
Human Complement ◽  
Complement Protein ◽  
Inhibitory Potency ◽  
Thiol Compounds ◽  
Binding Reaction ◽  
Binding Surface ◽  
Hypertensive Drug ◽  
Human Complement Component

Thiol compounds have been investigated as inhibitors of the covalent binding reaction of human complement protein C4 using Sepharose-C1s as a combined activating and binding surface. o- and p-substituted aminothiophenols are equally effective inhibitors, whereas the m-substituted compound is a less potent inhibitor. The anti-hypertensive drug captopril is also shown to inhibit the covalent binding reaction. A comparison of the effects of these compounds on the covalent binding reaction of isolated C4A and C4B has been made. Results suggest that a Pro-to-Leu substitution in C4B is likely to account for the differences in inhibitory potency of C4B compared with C4A observed with the aromatic inhibitors.

scholarly journals Non-enzymic activation of the covalent binding reaction of the complement protein C3

1983 ◽  
Vol 211 (2) ◽  
pp. 381-389 ◽  
Author(s):  
S K A Law
Keyword(s):  
Conformational Change ◽  
Hydroxy Group ◽  
Covalent Binding ◽  
Activation Mechanism ◽  
Complement Protein ◽  
Guanidinium Chloride ◽  
Cleavage Reaction ◽  
Binding Reaction ◽  
Physiological Conditions ◽  
Similar Dependence

The covalent binding of [3H]glycerol to C3 by the transfer of the acyl group of the internal thioester of C3 to the hydroxy group of glycerol can be activated either proteolytically by trypsin or by various chaotropes and denaturants. The activation of binding by trypsin or KBr showed similar dependence on the concentration of glycerol, indicating a similar activation mechanism. It is therefore concluded that the conformational change of the protein is the critical step in the binding reaction, and that the conversion of C3 into C3b under physiological conditions is only a means to induce the conformational change. Guanidinium chloride induces the binding of glycerol to C3 at concentrations of about 1 M. On increasing the concentration of guanidinium chloride the extent of binding declines and is accompanied by an increase in the autolytic cleavage reaction [Sim & Sim (1981) Biochem. J. 193, 129-141]. The autolytic cleavage reaction is therefore not independently activated with respect to the binding reaction. Its occurrence, however, is structurally restricted under physiological or limited denaturing conditions and is permissible only when C3 is brought to a higher denaturation state.

scholarly journals The effect of residue 1106 on the thioester-mediated covalent binding reaction of human complement protein C4 and the monomeric rat α-macroglobulin α1 I3

FEBS Letters ◽  
1995 ◽  
Vol 368 (1) ◽  
pp. 87-91 ◽  
Author(s):  
Xiang-Dong Ren ◽  
Alister W. Dodds ◽  
Jan J. Enghild ◽  
Charleen T. Chu ◽  
S.K. Alex Law
Keyword(s):  
Covalent Binding ◽  
Human Complement ◽  
Complement Protein ◽  
Binding Reaction

scholarly journals The degradation of cartilage proteoglycans by tissue proteinases. Proteoglycan structure and its susceptibility to proteolysis

1977 ◽  
Vol 167 (3) ◽  
pp. 629-637 ◽  
Author(s):  
P J Roughley ◽  
A J Barrett
Keyword(s):  
Ionic Strength ◽  
Cathepsin D ◽  
Core Protein ◽  
Degradation Products ◽  
Gradient Centrifugation ◽  
Limited Proteolysis ◽  
Extraction Procedure ◽  
Cathepsin G ◽  
Nasal Cartilage ◽  
Cscl Density Gradient

1. Proteoglycan was obtained from bovine nasal cartilage by a procedure involving sequential extraction with a low-ionic-strength KCl solution, then a high-ionic-strength CaCl2 solution. Purification was by CsCl-density-gradient centrifugation. 2. The CaCl2- extracted proteoglycan was subjected to proteolytic degradation by papain, trypsin, cathepsin D, cathepsin B, lysosomal elastase or cathepsin G. Degradation was allowed to proceed until no further decrease in viscosity was detectable. 3. The size and chemical composition of the final degradation products varied with the different proteinases. Cathepsin D and cathepsin G produced glycosaminoglycan-peptides of largest average size, and papain produced the smallest product. 4. The KCl-extracted proteoglycan was intermediate in molecular size and composition between the CaCl2-extracted proteoglycan and the largest final degradation products, and may have been formed by limited proteolysis during the extraction procedure. 5. It is postulated that the glycosaminoglycan chains are arranged in groups along the proteoglycan core protein. Proteolytic cleavage between the groups may be common to the majority of proteinases, whereas clevage within the groups is dependent on the specificity of each individual proteinase.

Surface properties of the bovine casein components: relationships between structure and foaming properties

1989 ◽  
Vol 56 (3) ◽  
pp. 495-502 ◽  
Author(s):  
Denis Lorient ◽  
Brigitte Closs ◽  
Jean Luc Courthaudon
Keyword(s):  
Surface Tension ◽  
Ionic Strength ◽  
Foam Stability ◽  
Covalent Binding ◽  
High Surface ◽  
Surface Hydrophobicity ◽  
Foaming Properties ◽  
Foam Formation ◽  
Foaming Capacity ◽  
Low Ionic Strength

SummaryIn order to optimize the use of caseins as surfactants, the surface tension, foaming capacity and stability were measured as a function of pH, ionic strength, protein concentration and polarity (modified by covalent binding of carbohydrates). We found that the caseins differ in their behaviour at the air/water interface with β-casein showing the greatest ability to decrease surface tension and to produce foams, due probably to its amphipathic structure. In experiments carried out at pH values close to pI, with low ionic strength and constant solubility (optimal conditions for foam formation), we observed a high surface hydrophobicity, a good accessibility and flexibility of peptidic side chains (evaluated by proteolysis), and a high foaming capacity parallelled by increased surface pressure. Foam stability of caseins was low compared to those of globular proteins such as β lactoglobulin.

scholarly journals Localization of Regions in CD46 That Interact with Adenovirus

2005 ◽  
Vol 79 (12) ◽  
pp. 7503-7513 ◽  
Author(s):  
Anuj Gaggar ◽  
Dmitry M. Shayakhmetov ◽  
M. Kathryn Liszewski ◽  
John P. Atkinson ◽  
André Lieber
Keyword(s):  
Measles Virus ◽  
Human Herpesvirus ◽  
Single Amino Acid ◽  
Complement Protein ◽  
Virus Binding ◽  
Protein Protein Interaction ◽  
Cellular Attachment ◽  
Binding Surface ◽  
Neisseria Gonorrhea ◽  
Group B

ABSTRACT A variety of pathogens use CD46, a ubiquitously expressed membrane protein that regulates complement activation, as a cellular attachment receptor. While the CD46 binding sites of several pathogens, including measles virus, Neisseria gonorrhea, and human herpesvirus 6, have been described, the region of CD46 responsible for adenovirus binding has not been determined. In this study, we used competition experiments with known CD46 ligands, CD46-specific antibodies, and a set of CD46 mutants to localize the binding domain for the group B adenovirus serotype 35 (Ad35). Our results show that Ad35 competes with measles virus for binding to CD46 but not with complement protein C3b. We further show that this interaction is a protein-protein interaction and that N glycosylations do not critically contribute to infection with Ad35 fiber-containing Ad vectors. Our data demonstrate that the native conformation of the CCP2 domain is crucial for Ad35 binding and that the substitution of amino acids at positions 130 to 135 or 152 to 156 completely abolishes the receptor function of CD46. These regions localize to the same planar face of CD46 and likely form an extended adenovirus binding surface, since no single amino acid substitution within these areas eliminates virus binding. Finally, we demonstrate that the infection with a virus possessing human group B serotype Ad11 fibers is also mediated by the CCP2 domain. This information is important to better characterize the mechanisms of the receptor recognition by adenovirus relative to other pathogens that interact with CD46, and it may help in the design of antiviral therapeutics against adenovirus serotypes that use CD46 as a primary cellular attachment receptor.

scholarly journals Kinetic, Catalytic and Thermodynamic Properties of Immobilized Milk Clotting Enzyme on Activated Chitosan Polymer and its Application in Cheese Making

2021 ◽  
Author(s):  
Samia Ahmed ◽  
Mohamed A. Abdel-Naby ◽  
Ahmed F. Abdel-Fattah
Keyword(s):  
Covalent Binding ◽  
Catalytic Efficiency ◽  
Life Time ◽  
Industrial Applications ◽  
Maximum Reaction Rate ◽  
Milk Clotting ◽  
Milk Clotting Enzyme ◽  
Specificity Constant ◽  
Optimum Reaction ◽  
Ionic Binding

Abstract Milk clotting enzyme (MCE) from Bacillus circulans 25 was immobilized by covalent binding, ionic binding and entrapment methods using various carriers. MCE covalently immobilized on activated chitosan polymer with the bifunctional agent glutaraldehyde (Ch-MCE) exhibited highest immobilization yield (74.6 %). Comparing to the native MCE, Ch-MCE exhibited higher optimum pH, higher optimum reaction temperature, lower activation energy, higher half-life time, lower deactivation rate constant and higher energy for denaturation. After immobilization, maximum reaction rate, Michaelis-Menten constant, specificity constant, turnover number, and catalytic efficiency of the enzyme were significantly changed. Calculated thermodynamic parameters for denaturation (enthalpy, entropy and Gibbs free energy) confirmed that the catalytic properties of MCE were significantly improved after immobilization. Reusability tests showed that after 7 catalytic cycles, the Ch-MCE retained about 71 % of its activity confirming its suitability for industrial applications.

Identification of the Binding Surface on β-Lactamase for GroEL by Limited Proteolysis and MALDI-Mass Spectrometry†

Biochemistry ◽  
1998 ◽  
Vol 37 (33) ◽  
pp. 11660-11669 ◽  
Author(s):  
Pietro Gervasoni ◽  
Werner Staudenmann ◽  
Peter James ◽  
Andreas Plückthun
Keyword(s):  
Mass Spectrometry ◽  
Limited Proteolysis ◽  
Maldi Mass Spectrometry ◽  
Binding Surface
Sign in / Sign up

Export Citation Format

Share Document