Plasma concentrations of C4b-binding protein and vitamin K-dependent protein S in term and preterm infants: low levels of protein S-C4b-binding protein complexes

1988 ◽  
Vol 68 (4) ◽  
pp. 445-449 ◽  
Author(s):  
Johan Malm ◽  
Rolf Bennhagen ◽  
Lars Holmberg ◽  
Björn Dahlbäck
Keyword(s):  
Preterm Infants ◽  
Vitamin K ◽  
Protein Complexes ◽  
Binding Protein ◽  
Plasma Concentrations ◽  
Protein S ◽  
Dependent Protein ◽  
Low Levels

LOW PLASMA CONCENTRATIONS OF C4b-BINDING PROTEIN AND VITAMIN K-DEPENDENT PROTEIN S IN PRETERM INFANTS WITH DECREASED FORMATION OF PROTEIN S-C4b-BINDING PROTEIN COMPLEXES

1987 ◽  
Author(s):  
J Malm ◽  
R Bennhagen ◽  
L Holmberg ◽  
B Dahlbäck
Keyword(s):  
Preterm Infants ◽  
Vitamin K ◽  
Total Protein ◽  
Binding Protein ◽  
Plasma Concentrations ◽  
Protein S ◽  
Complement Protein ◽  
Term Infants ◽  
Free Protein ◽  
Adult Level

Protein S is a vitamin K-dependent plasmaprotein functioning as a non-enzymatic cofactor to the activated form of protein C in the degradation of coagulationfactors Va and VIIa. In the circulation approximately 60% of protein S is complexed to the complement protein C4b-binding protein (C4BP). Only the remaining, free fraction exhibits protein Ca cofactor activity.The plasma concentrations of protein S and C4BP were determined in 25 term and 26 preterm infants. Both proteins werequantified with radioimmunoassays. The free, functionally active form of proteinS and the total protein S concentration were determined separately. The level ofC4BP in preterm infants was found to be very low (mean 6% of the adult level). In term infants the level had increased to a mean of 18%. Also the total concentration of protein S was decreased in preterm as well as in term infants; 18% and 31% of the adult level, respectively. Free protein S was the predominant form in plasma representing 83 % of total protein S in preterm and 68 % in term infants. This was probably due to the very low C4BP levels. In adult controls the corresponding value was 34%. The plasma concentration of free protein S in preterm and term infants, when compared to the adult level, was 44% and 66%, respectively. These results demonstrate that although the total protein S concentration in preterm and term infants was very low when compared to adult levels, the difference in the concentration of free, functionally active protein S between infants and adults was less pronounced.

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.

scholarly journals Purification of human vitamin K-dependent protein S and its limited proteolysis by thrombin

1983 ◽  
Vol 209 (3) ◽  
pp. 837-846 ◽  
Author(s):  
B Dahlbäck
Keyword(s):  
Vitamin K ◽  
Gel Electrophoresis ◽  
Binding Protein ◽  
Sodium Dodecyl ◽  
Limited Proteolysis ◽  
Protein S ◽  
Single Chain ◽  
Free Protein ◽  
Reducing Conditions ◽  
Dependent Protein

Vitamin K-dependent protein S exists in two forms in human plasma, namely as the free protein and in complex with C4b-binding protein [Dahlbäck & Stenflo (1981) Proc. Natl. Acad. Sci. U.S.A. 78, 2512-2516]. Now reported is a simple purification procedure for human protein S that includes barium citrate adsorption, DEAE-Sephacel chromatography and chromatography on Blue Sepharose. The yield was approx. 30% relative to the concentration of free protein S in plasma, which was found to be approx. 10 mg/l. Purified protein S migrated as a single-chain band on sodium dodecyl sulphate/polyacrylamide-gel electrophoresis under non-reducing conditions and as a doublet of Mr approx. 85 000 and 75 000 on reduction. A third band of Mr 16 000 was observed after electrophoresis of 125I-labelled protein S and radioautography of reduced samples. This band appears to be disulphide-linked to the 75 000-Mr chain before reduction. Thrombin converted the 85 000-Mr chain of protein S into a 75 000-Mr chain and an 8000-Mr fragment, the latter again being detectable only by radioautography of reduced samples. The 16 000-Mr fragment was not observed, suggesting its degradation by thrombin. Under non-reducing conditions, no change in apparent molecular weight of thrombin-treated protein S was observed, indicating disulphide linkage of the fragments. Thrombin also affected the mobility of protein S on agarose-gel electrophoresis in the presence of Ca2+, suggesting a decreased affinity to Ca2+ of the cleaved form of protein S as compared with the undegraded molecule. After activation of the complement system in human serum, protein S was found to be a constituent part of the complex formed by C4b-binding protein and component C4b.

scholarly journals Purification of human C4b-binding protein and formation of its complex with vitamin K-dependent protein S

1983 ◽  
Vol 209 (3) ◽  
pp. 847-856 ◽  
Author(s):  
B Dahlbäck
Keyword(s):  
Molecular Weight ◽  
Complex Formation ◽  
Vitamin K ◽  
Gel Electrophoresis ◽  
Binding Protein ◽  
Protein S ◽  
Agarose Gel ◽  
Agarose Gel Electrophoresis ◽  
Dependent Protein ◽  
Molecular Weight Form

C4b-binding protein was purified from human plasma in high yield by a simple procedure involving barium citrate adsorption and two subsequent chromatographic steps. Approx. 80% of plasma C4b-binding protein was adsorbed on the barium citrate, presumably because of its complex-formation with vitamin K-dependent protein S. The purified C4b-binding protein had a molecular weight of 570 000, as determined by ultracentrifugation, and was composed of about eight subunits (Mr approx. 70 000). Uncomplexed plasma C4b-binding protein was purified from the supernatant after barium citrate adsorption. On sodium dodecyl sulphate/polyacrylamide-gel electrophoresis in non-reducing conditions and on agarose-gel electrophoresis it appeared as a doublet, indicating two forms differing slightly from each other in molecular weight and net charge. The protein band with the higher molecular weight in the doublet corresponded to the C4b-binding protein purified from the barium citrate eluate. Complex-formation between protein S and C4b-binding protein was studied in plasma, and in a system with purified components, by an agarose-gel electrophoresis technique. Protein S was found to form a 1:1 complex with the higher-molecular-weight form of C4b-binding protein, whereas the lower-molecular-weight form of C4b-binding protein did not bind protein S. The KD for the C4b-binding protein-protein S interaction in a system with purified components was approx. 0.9×10(-7) M. Rates of association and dissociation at 37 degrees C were low, namely about 1×10(3) M-1 . S-1 and 1.8×10(-4)-4.5×10(-4) S-1 respectively. In human plasma free protein S and free higher-molecular-weight C4b-binding protein were in equilibrium with the C4b-binding protein-protein S complex. Approx. 40% of both proteins existed as free proteins. From equilibrium data in plasma a KD of about 0.7×10(-7) M was calculated for the C4b-binding protein-protein S interaction.

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