scholarly journals Expression and characterization of a recombinant C4b-binding protein lacking the β-chain

1995 ◽  
Vol 308 (3) ◽  
pp. 795-800 ◽  
Author(s):  
Y Härdig ◽  
P García de Frutos ◽  
B Dahlbäck
Keyword(s):  
Molecular Mass ◽  
Binding Protein ◽  
Expression System ◽  
Activated Protein C ◽  
Protein S ◽  
High Molecular Mass ◽  
Eukaryotic Expression ◽  
Beta Chain ◽  
Factor I ◽  
Dependent Protein

C4b-binding protein (C4BP) is a high-molecular-mass glycoprotein which contains binding sites for complement component C4b, anti-coagulant vitamin K-dependent protein S and serum amyloid P component (SAP). The major form of C4BP in plasma is composed of seven identical alpha-chains and a single beta-chain. We have expressed full-length cDNA for the alpha-chain in a eukaryotic expression system and characterized functional properties of non-beta-chain-containing C4BP. During synthesis, recombinant alpha-chains polymerized into two different high-molecular-mass C4BP forms which were composed of seven or eight alpha-chains. Recombinant C4BP bound C4(H2O) (used instead of C4b) equally as well as native C4BP, functioned equally as well as factor I cofactor in the degradation of C4(H2O) and bound to SAP. In contrast, the recombinant C4BP did not bind protein S and therefore did not inhibit the ability of protein S to function as a cofactor to activated protein C. Tunicamycin treatment of the transfected cells prevented N-linked glycosylation, but did not affect polymerization of the alpha-chains into a high-molecular-mass C4BP. The non-glycosylated C4BP had comparable properties to glycosylated C4BP in several functional assays. These results demonstrate polymerization of C4BP alpha-chains to be independent both of the beta-chain and of the N-linked carbohydrates. Moreover, N-linked carbohydrates and the beta-chain were neither required for the ability of C4BP to bind C4b and to function as factor I cofactor nor for the interaction with SAP.

scholarly journals Degradation of human complement component C4b in the presence of the C4b-binding protein-protein S complex

1983 ◽  
Vol 209 (3) ◽  
pp. 857-863 ◽  
Author(s):  
B Dahlbäck ◽  
B Hildebrand
Keyword(s):  
Binding Sites ◽  
Binding Protein ◽  
Sodium Dodecyl ◽  
Fluid Phase ◽  
Protein S ◽  
Factor I ◽  
Haemolytic Assay ◽  
Dependent Protein ◽  
Molecular Weight Form ◽  
Human Complement Component

Vitamin K-dependent protein S and the higher-molecular-weight form of C4b-binding protein (C4bp-high) interact, forming a 1:1 complex with a KD of approx. 1×10(-7) M [Dahlbäck (1983) Biochem. J. 209, 847-856]. In the present study the effect of protein S on the degradation of C4b by Factor I (C3b inactivator) and C4bp was investigated both in fluid phase and on cell surfaces, with the use of highly purified components. Fluid-phase degradation of C4b was monitored on sodium dodecyl sulphate/polyacrylamide-slab-gel electrophoresis, and the effect on surface-bound C4b was estimated by haemolytic assay. No effect of protein S could be demonstrated in any of the systems used. Thus, although bound to C4bp, protein S is neither involved in, nor does it affect, the interaction between C4bp and C4b. This indicates that the binding sites on the C4bp molecule for protein S and for C4b are independent and different.

scholarly journals Vitamin K-dependent protein S is similar to rat androgen-binding protein

1987 ◽  
Vol 243 (1) ◽  
pp. 293-296 ◽  
Author(s):  
M E Baker ◽  
F S French ◽  
D R Joseph
Keyword(s):  
Vitamin K ◽  
Binding Protein ◽  
Protein A ◽  
Serine Proteinase ◽  
Protein S ◽  
Clotting Factors ◽  
The Family ◽  
Androgen Binding Protein ◽  
Dependent Protein ◽  
Androgen Binding

Vitamin K-dependent protein S belongs to the family of clotting factors (e.g. Factors IX and X, and protein C). Unlike the other clotting factors, the C-terminal half (residues 250-634) of protein S is not a serine proteinase. In fact, the function of residues 250-634 of protein S is unknown. By using computer programs designed to detect evolutionary relationships between proteins, we find that this part of protein S is similar to rat androgen-binding protein, a protein produced and secreted by testicular Sertoli cells. The homology between protein S and androgen-binding protein suggests new approaches for elucidating their functions.

Coagulation, inflammation, and apoptosis: different roles for protein S and the protein S–C4b binding protein complex

Blood ◽  
2004 ◽  
Vol 103 (4) ◽  
pp. 1192-1201 ◽  
Author(s):  
Suely Meireles Rezende ◽  
Rachel Elizabeth Simmonds ◽  
David Anthony Lane
Keyword(s):  
Venous Thromboembolism ◽  
Complement Activation ◽  
Protein C ◽  
Binding Protein ◽  
Anticoagulant Activity ◽  
Activated Protein C ◽  
Protein S ◽  
Increased Risk ◽  
Established Role ◽  
Structure And Functions

AbstractProtein S (PS) has an established role as an important cofactor to activated protein C (APC) in the degradation of coagulation cofactors Va and VIIIa. This anticoagulant role is evident from the consequences of its deficiency, when there is an increased risk of venous thromboembolism. In human plasma, PS circulates approximately 40% as free PS (FPS) and 60% in complex with C4b-binding protein (C4BP). Formation of this complex results in loss of PS cofactor function, and C4BP can then modulate the anticoagulant activity of APC. It had long been predicted that the complex could act as a bridge between coagulation and inflammation due to the involvement of C4BP in regulating complement activation. This prediction was recently supported by the demonstration of binding of the PS-C4BP complex to apoptotic cells. This review aims to summarize recent findings on the structure and functions of PS, the basis and importance of its deficiency, its interaction with C4BP, and the possible physiologic and pathologic importance of the PS-C4BP interaction.

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