Low solubility fibrinogen examined by two-dimensional sodium dodecyl sulfate gel electrophoresis and isoelectric focusing

Location of the binding site "b" for lateral polymerization of fibrin

We examined the location of the binding site "b" for lateral polymerization of fibrin using two fractions of normal human fibrinogen, a high-molecular weight fraction (so-called normal fibrinogen) and a low-molecular weight fraction which lacks the C-terminal half of one of its two A alpha chains, and Gly-His-Arg-Pro, a synthetic peptide that corresponds to the N-terminal sequence of human fibrin beta chain and binds specifically to the site "b". The amounts of the synthetic peptide bound to each of the low- and high-molecular weight fractions were 1 mol/mol and 2 mol/mol, respectively. The peptide delayed the clotting of fibrinogen by blocking the site "b", but did not inhibit thrombin at all. In the presence of the peptide, the high-molecular weight fraction did not form a normal coarse clot but a fine clot which was identical to that produced by the low-molecular weight fraction. The identity of the two clots was judged from four different points: morphology, turbidity, elasticity and clotting velocity of fibrin. The results suggest that the site "b" is located within the portion of the fibrinogen molecule present in the high-molecular weight fraction, but not in the low-molecular weight fraction and that the site "b" plays an essential role in the lateral polymerization of fibrin.

Polymerization properties of two normally circulating fibrinogens, HMW and LMW. Evidence that the COOH-terminal end of the a-chain is of importance for fibrin polymerization

The plasma fibrinogen fractions HMW (mw 340,000) and LMW (mw 305,000) were prepared from purified (beta-alanine precipitated) fibrinogen by step-wise precipitation with ammonium sulfate. The thrombin clotting times were 14" and 20" respectively. The enzymatic phase of coagulation, measured as release of fibrinopeptide-A during incubation with thrombin, was found to be identical for HMW and LMW. Polymerization was studied by light scattering (at 605 nm) using preformed monomers (des-AA and des-AABB) prepared from HMW and LMW in the presence of 3.3 M urea by incubation with thrombin (100 NIH U/ml final conc.) and reptilase (1 U/ml final conc.). The HMW-monomers polymerised at a substantially higher rate than the corresponding LMW-monomers. Thus, the prolonged clotting time of LMW was explained by retarded polymerization. It is suggested that the -COOH terminal end of the a-chain, containing the molecular difference between HMW and LMW, is of importance for polymerization. Furthermore, the release of fibrinopeptide B (des-AABB-monomers) improved polymerization properties in HMW as well as in LMW, and all types of monomers polymerised more rapidly in the presence of Ca++.

Purification and characterization of 3 fibrinogens with different molecular weights obtained from normal human plasma

Fibrinogen was purified from fresh citrated human plasma by precipitation with beta-alanine in the presence of citrate and protease inhibitors. From this material, fractions corresponding to the HMW (high molecular weight), LMW and LMW' fibrinogen fractions of plasma were obtained by step-wise precipitation with ammonium sulfate. Electrophoresis revealed that HMW was contaminated with 4% LMW, LMW was contaminated with 6% HMW, and the LMW'-fraction was a mixture of LMW' (50%), LMW (20%) and two derivatives of intermediate m.w.. The HMW fraction (mw. 340 000) contained intact Aa-chains, while the molecular weight of LMW was reduced to 305 000 and that of LMW' to 270 000 due to proteolysis of the -COOH terminal end of one (LMW) or both (LMW') Aa-chains. The clottability of HMW was 98%, of LMW 92% and of LMW' about 80%. Thrombin clotting times (1 NIH U/ml) were 14", 20" and 25" resp. These differences were highly accentuated when clotting was performed with reptilase (14", 38" and 120"). Contamination with soluble fibrin was less than 2% and the contents of fibronectin and AT-III were low. No thrombin or plasmin activity was generated upon 24 hours incubation at +4 degrees C as evidenced by increased content of fibrinopeptide-A and fragment Bb-15-42 resp.

Quantitation of the three normally-occurring plasma fibrinogens in health and during so-called "acute phase" by SDS electrophoresis of fibrin obtained from EDTA-plasma

Normal human plasma contains fibrinogens of different molecular weight. To quantitate these fibrinogens, plasma was clotted at pH 6.4 with 7.5 NIH U/ml thrombin in the presence of 8 mM EDTA. The clots were dissolved in 6.6 M urea and submitted to SDS electrophoresis on gels containing 3% polyacrylamide/0.5% agarose, and the fractions quantitated by densitometric scanning. The reproducibility of this method was high with variation coefficient 1.5%. Three main fibrinogen fractions were found: High molecular weight fibrinogen (HMW, mw 340 000), low molecular weight fibrinogen (LMW, mw 300 000) and LMW' (mw 280 000). In addition 5 weak bands could be seen. In plasma from 123 healthy subjects of both sexes, aged 1-93 years, HMW constituted 69.7% +/- 5.1, LMW 26.5% +/- 4.8 and LMW' 3.8% +/- 1.8 of the total fibrinogen. Women and older subjects displayed a small, but statistically significant reduction in the relative amounts of HMW (2-4%). Following surgery and extensive acute myocardial infarction the HMW/LMW ratio changed. The substantial increase in total fibrinogen regularly recorded was mainly due to HMW that reached maximal values after 3-4 days. LMW remained unchanged the first 2 days and then displayed a slight increase with a delayed maximum (8-11 days).

Fibrinogen Adelaide: a familial hypodysfibrinogenaemia associated with abnormal alpha chains

A familial hypodysfibrinogenaemia occurring in four females with occasional haemorrhagic problems in an Adelaide family was investigated. Affected family members had slightly prolonged thrombin time, prothrombin time and Reptilase time tests, and apparently elevated levels of fibrin degradation products (FDPs). Fibrinogen assessed by reactivity with thrombin (Clauss method) was significantly less than fibrinogen determined by various other methods, though even by immunoquantitation fibrinogen levels were only slightly above half normal in affected family members. Isoelectric focussing (IEF) of the reduced patient's fibrinogen in urea/polyacrylamide gel revealed minor components with higher isoelectric points (pI) than present in normal fibrinogen or fibrin. These were shown to have a molecular weight similar to the alpha chain of fibrin by subsequent sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE). The abnormal species tended to remain in plasma after clotting with Reptilase or thrombin although polymerization of the clotted fibrin was normal. The magnitude of the pI shift relative to normal fibrin alpha chain indicated an increased positive charge on the abnormal species.

Immunocytochemical localization of fibrinogen, platelet factor 4, and beta thromboglobulin in thin frozen sections of human blood platelets

Affinity-purified monospecific antibodies against human fibrinogen and the platelet-specific proteins platelet factor 4 and beta thromboglobulin were used to localize these antigens in thin and ultra-thin frozen sections of mildly fixed, washed human blood platelets. By immunofluorescent double-labeling experiments the distribution of fibrinogen was compared to that of platelet factor 4 and beta thromboglobulin. All three antigens occurred in virtually all platelets and showed and identical, dotlike distribution. For immunoelectron microscopy we used protein A-colloidal gold on ultra-thin frozen sections to visualize the specific reaction indirectly. The staining for platelet factor 4, beta thromboglobulin, and fibrinogen localized exclusively over alpha-granules of washed platelets. Within the granules, platelet factor 4 was localized preferentially in the electron dense, alpha-granule nucleoid, whereas fibrinogen was more predominant in the electron-lucent granule periphery. Beta thromboglobulin localization did not show a preferential intragranular distribution.

Plasma protein binding by monosodium urate crystals. Analysis by two-dimensional gel electrophoresis

Using 2-dimensional O'Farrell gel electrophoresis, we have mapped the proteins from undiluted plasma and serum which bind to monosodium urate (MSU) crystals. More than 30 crystal-associated polypeptides were visualized, including anionic and cationic species. Proteins increased on the crystals relative to plasma included C1q, C1-r, C1-s, fibronectin, fibrinogen, and kininogen. Crystal-bound polypeptides derived from IgG, albumin, and transferrin were recovered in decreased amounts relative to plasma. Direct evidence for activation of the complement and coagulation systems in plasma was provided by the identification of crystal-associated activation fragments of C1 and kininogen. Plasmas deficient in selected proteins (e.g., C1q and IgG) were used to define the role of these proteins in such activation events and confirmed activation of C1 in immunoglobulin-deficient plasma by MSU crystals. In summary, we have described a high resolution, semiquantitative approach to analyze protein binding to crystals, have documented the complexity of crystal-plasma protein interaction, and have provided direct evidence for the binding of coagulation system proteins and binding and activation of complement by MSU crystals, in whole plasma and IgG-deficient plasma.

Structural analysis of fibrinogen synthesized by cultured chicken hepatocytes in the presence or absence of dexamethasone

Hepatocyte monolayers, derived from chick embryos and cultured in chemically defined medium without hormones, synthesize and secrete fibrinogen that resembles chicken plasma fibrinogen immunochemically and structurally. Addition of a synthetic glucocorticoid, dexamethasone, to the cultured cells resulted in an appreciable and relatively selective increase in fibrinogen synthesis. Autoradiography of fibrinogen that had been metabolically labelled with [35S]methionine and then subjected to SDS-polyacrylamide gel electrophoresis, unreduced or under disulfide-reducing conditions, revealed that only dimeric forms of fibrinogen, containing undegraded A alpha, B beta, and gamma chains, were secreted under stimulated and unstimulated culture conditions.