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Query: UNIPROT:P06889 (Mol)
 630,302 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Fibrin-specific antibodies have been produced in rabbits which were immunized with synthetic peptides. Specificity against human fibrin monomer was achieved because the synthetic peptide haptens were derived from sites unique to fibrin as compared with fibrinogen. Two undecapeptides were chemically synthesized according to the amino acid sequence of the amino termini of human fibrin alpha- and beta-chains which are revealed by thrombin cleavage. Rabbits immunized with either an alpha- or beta-chain peptide conjugate produced anti-peptide sera which reacted with fibrin monomer. Following immunoadsorption of the rabbit sera with human fibrinogen-Sepharose, fibrin-specific antibodies were detectable by solid-phase radioimmunoassay that did not react with fibrinogen. Antisera elicited by clotted human fibrin contained antibodies that reacted with fibrin and fibrinogen when treated in a similar manner.
Mol Immunol 1983 May
PMID:Induction of fibrin-specific antibodies by immunization with synthetic peptides that correspond to amino termini of thrombin cleavage sites. 634 13

Trichomonas vaginalis avidly bound numerous host macromolecules which were not removed by repeated washing in phosphate buffered saline. The use of radioiodinated Cohn plasma fractions in binding studies allowed the identification of plasminogen, fibrinogen, immunoglobulin G, lipoproteins A and B, transferrin, alpha 1-antitrypsin, and albumin on intact organisms. The binding of immunoglobulin G, albumin, transferrin, and lipoproteins to intact, motile trichomonads was further demonstrated using 125I-labeled plasma that was chromatographically depleted of these proteins. Kinetic studies indicated that 125I-labeled lipoproteins bind to T. vaginalis in a receptor-ligand-like manner. The surface localization and uptake of bound lipoproteins was shown by treatment of intact organisms with pronase at various times after incubation with lipoproteins. Purified lipoproteins could be substituted for plasma or serum as a growth supplement in a complex medium of trypticase/yeast extract/maltose and supported growth and multiplication rates equal to those in the same medium with plasma.
Mol Biochem Parasitol 1984 May
PMID:Selective acquisition of plasma proteins by Trichomonas vaginalis and human lipoproteins as a growth requirement for this species. 637 53

We purified and characterized the mRNAs coding for each of the three subunits of Xenopus fibrinogen. Purification was accomplished by electrophoretic separation of liver polyadenylated RNA in a fully denaturing gel, followed by recovery of the RNA from the gel via transfer to an ion-exchange membrane. This procedure yielded fractions which were highly enriched for the mRNAs for each of the fibrinogen chains. The fibrinogen mRNAs were identified by two methods: (i) in vitro translation followed by subunit-specific cleavage with the proteases thrombin and batroxobin; and (ii) cross-hybridization with cDNA clones for individual subunits of rat fibrinogen. The results demonstrate that the A alpha and gamma chains of frog fibrinogen are each coded by a single mRNA species. The A alpha mRNA is ca. 3,100 nucleotides in length, which is nearly twice the minimum size required to code for the A alpha precursor polypeptide. The gamma chain mRNA comprises about 1,600 bases and includes only a small untranslated region. In contrast, the B beta subunit is synthesized from two mRNAs, one of which is 2,500 and the other 1,800 nucleotides long. The 2,500-base mRNA includes a large noncoding region, whereas the smaller one is near the minimum required size. The larger B beta mRNA is ca, fivefold more abundant that the smaller species.
Mol Cell Biol 1984 Nov
PMID:Xenopus fibrinogen: characterization of the mRNAs for the three subunits. 651 31

The structure of proteolytically modified fibrin and a closely related modified fibrinogen aggregate have been studied by analysis of electron microscope images. For both structures, we propose a model that consists of double-stranded, 2-fold helical protofibrils, which are associated laterally to form ordered fibrils, with a C222 space group: a = 44.0 nm, b = c = 9.4 nm. Each fibril is 80 nm or less in diameter, and twists along its length in a right-handed sense, with a pitch from 7 to 12 times the molecular length. The fibrils associate laterally to form bundles, which tend to twist in a left-handed sense, with a pitch of the order of 40 times the molecular length. The specific volume of modified fibrin calculated from this model is 3.9 A3 per dalton, which is comparable to the specific volume of 3.6 A3 per dalton for modified fibrinogen crystals but is lower than the 6 A3 per dalton determined for fibrin from light-scattering experiments. Comparison of our electron microscope results with X-ray and neutron diffraction data suggest a similar, but less well-ordered, structure for native fibrin, with a smaller fibril, approximately 18.4 nm wide, consisting of eight protofibrils.
J Mol Biol 1983 Oct 15
PMID:Electron microscope structural study of modified fibrin and a related modified fibrinogen aggregate. 663 61

A stable hybridoma secreting homogeneous antibody (immunoglobulin class IgG2a) has been prepared by fusion using cells of immunoglobulin non-secreter myeloma (P3X63Ag8.653) and spleen cells of mice which had previously been immunized with the NH2-terminal CNBr fragment of human fibrinogen, the so-called N-DSK [(A alpha 1-51, B beta 1-118, gamma 1-78)2]. In competitive ELISA or radioimmunoassay this antibody (MAb/1-8C6) cross-reacted with intact fibrinogen, N-DSK, a des fibrinopeptide A (des FPA) variant of N-DSK, the so-called (B)N-DSK, as well as the intact B beta chain (B beta 1-118) obtained from N-DSK. Also, and mot importantly, cross-reactivity was observed with fibrinogen-free ethanol extracts of plasma obtained from patients known to contain high levels of fibrinogen or fibrin degradation products. In vitro thrombin digestion of any of these competitors resulted in complete loss of cross-reactivity. MAb/1-8C6 did not react with the A alpha or gamma-chains of N-DSK, free fibrinopeptide B(FPB), free B beta 15-42, as well as equimolar mixtures of the latter two peptides. These results suggest that MAb/1-8C6 may be to an epitope in or around the thrombin-susceptible B beta 14 Arg-25 Gly bond. Furthermore, due to its reactivity with patient plasma extracts, this antibody may be useful in clinical investigations dealing with fibrino(geno)lysis.
Mol Immunol 1983 Nov
PMID:A monoclonal antibody with ability to distinguish between NH2-terminal fragments derived from fibrinogen and fibrin. 665 69

High molecular weight fragment D (M.W. 95 000) which is an effective inhibitor of polymerization of fibrin, and its more low molecular weight form (M.W. 82 000) which has no antipolymerization activity was obtained from fibrinogen by proteolysis. It was shown by the method of scanning microcalorimetry that the active D-fragment consists of four cooperative regions: one thermostable and three non-equal thermolabile. The smallest thermolabile cooperative region (M.W. 13 000) in the inactive D-fragment is absent. It is supposed, that it takes part in the formation of the active centre.
Mol Biol (Mosk)
PMID:[Isolation and investigation of structural organization of active and inactive forms of fibrinogen D-fragment molecule]. 715 39

Melting of fibrinogen and its proteolytic fragments has been studied by differential scanning microcalorimetry. It has been shown that the fibrinogen molecule contains at least nine cooperative regions. One of them pertains to the central structural block (domain E), two of them are formed by the structures removed at proteolytic fragmentation and the others make part of the terminal structural blocks (domains D). A scheme of localization of melting regions in the fibrinogen molecule is proposed on the basis of the results obtained.
Mol Biol (Mosk)
PMID:[Microcalorimetric studies of temperature transitions in fibrinogen and its proteolytic fragments]. 742 6

Temperature dependent studies of the interaction of the clotting enzyme thrombin with the potent natural inhibitor hirudin reveal a large negative heat capacity change of -1.7(+/- 0.2) kcal/mol per K associated with the formation of the thrombin-hirudin complex, independent of the allosteric state of the enzyme. Binding of N-terminal fragments of hirudin (hir1-49 and hir1-43) is characterized by heat capacity changes of -1.2(+/- 0.1) and -0.9(+/- 0.1) kcal/mol per K, respectively. The magnitude of these heat capacity changes is unprecedented for protease-inhibitor interactions. A thermodynamic analysis based on observed heat capacity and entropy changes predicts that binding is accompanied by substantial coupled folding transitions in both hirudin and thrombin. In the absence of a structure of free thrombin, analysis of differences in the predicted number of residues which fold upon binding hirudin and its fragments leads to the following structural model: three surface loops in thrombin (W60d, W148 and fibrinogen binding loops) are disordered in the free state and fold upon formation of the thrombin-hirudin complex. Molecular dynamics simulations, run over a time scale of 5 ps, are consistent with the hypothesis of large scale coupled folding transitions in both hirudin and thrombin upon formation of the complex. Comparison of the thermodynamics for the interaction of hirudin with the slow and fast forms of thrombin allows dissection of the coupling free energy for allosteric switching. The coupling free energy for the slow-->fast transition increases linearly, in absolute value, with temperature. The coupling enthalpy and entropy terms for hirudin were found to be delta Hoc = 12(+/- 1) kcal/mol and delta Soc = 47(+/- 4) cal/mol per K. Preferential interaction with the fast form is therefore due to the balance of two opposite forces, both quite large in magnitude. The contribution of enthalpic effects opposes the slow-->fast transition and stabilizes binding to the slow form. The contribution of entropic effects favors the slow-->fast transition and stabilizes binding to the fast form. In the physiological temperature range the entropic effects prevail and result in preferential binding of hirudin to the fast form. The region of thrombin recognizing the N-terminal domain of hirudin contains most of the residues that are energetically linked to the slow-->fast transition. This region is part of the "allosteric core" of thrombin and includes the W60d loop, shaping the specificity site S2, and the Na+ binding loop connecting the last two beta-strands of the B chain.
J Mol Biol 1995 Nov 10
PMID:Thermodynamic investigation of hirudin binding to the slow and fast forms of thrombin: evidence for folding transitions in the inhibitor and protease coupled to binding. 747 52

The ability of Staphylococcus aureus to bind to fibrinogen and fibrin is believed to be an important factor in the initiation of foreign-body and wound infections. Recently, we reported the cloning and sequencing of the gene clfA encoding the fibrinogen receptor (clumping factor, ClfA) of S. aureus strain Newman and showed that the gene product was responsible for the clumping of bacteria in soluble fibrinogen and for the adherence of bacteria to solid-phase fibrinogen. This was confirmed here by showing that antibodies raised against purified Region A inhibited both of these properties. Also, immunofluorescent microscopic analysis of wild-type Newman and a clfA::Tn917 mutant of Newman with anti-ClfA Region A sera confirmed that Region A is exposed on the bacterial cell surface. Furthermore, polystyrene beads coated with the Region A protein formed clumps in soluble fibrinogen showing that the ClfA protein alone is sufficient for the clumping phenotype. Western immunoblotting with anti-ClfA Region A antibodies identified the native ClfA receptor as a 185 kDa protein that was released from the cell wall of S. aureus by lysostaphin treatment. A single extensive ligand-binding site was located within Region A of the ClfA protein. Truncated ClfA proteins were expressed in Escherichia coli. Lysates of E. coli and proteins that had been purified by affinity chromatography were tested for (i) their ability to bind fibrinogen in Western ligand blotting experiments, (ii) for their ability to inhibit clumping of bacteria in fibrinogen solution and adherence of bacteria to solid-phase fibrinogen, and (iii) for their ability to neutralize the blocking activity of anti-ClfA Region A antibody. These tests allowed the ligand-binding domain to be localized to a 218-residue segment (residues 332-550) within Region A.
Mol Microbiol 1995 Jun
PMID:Identification of the ligand-binding domain of the surface-located fibrinogen receptor (clumping factor) of Staphylococcus aureus. 747 87

We have determined that ADP-induced platelet aggregation and secretion are enhanced by preincubation of human platelets with the immunosuppressant cyclosporine A (CSA) (see accompanying article by Naik et al., 1993). In the present report we compare the effects of CSA with two other potent immunosuppressants, cyclosporine G (CSG), an analogue of CSA, and FK-506, on platelet activation. Preincubation of platelets with either CSA, CSG, or FK-506 resulted in platelets which exhibited hyperaggregability when stimulated by ADP. CSG produced the lowest degree of hyperaggregation, whereas FK-506 produced the highest at an equivalent concentration. All three compounds enhanced the secretion of serotonin, with FK-506 producing the highest degree of serotonin release and CSG producing the lowest amount. Platelet hyperaggregation and enhanced secretion were both time- and dose-dependent. Comparative studies performed with CSA and CSG indicated that a short preincubation period with CSA (2.5 min) resulted in a 90% enhancement of ADP-induced platelet aggregation, whereas CSG enhancement was only 20%. At a concentration of 600 ng/ml, CSA produced 120% enhancement of ADP-induced platelet aggregation, whereas CSG produced only a 30% enhancement. Several potential mechanisms responsible for the enhanced ADP-induced aggregation and secretion were investigated. Determination of the binding of two radiolabeled probes directed against the fibrinogen receptor, fibrinogen itself, and a monoclonal antibody (M.Ab.G10) revealed that the binding of fibrinogen to ADP-stimulated platelets was enhanced by 50% following the preincubation of platelets with 600 ng/ml CSA. Smaller, yet significant enhancement occurred in the presence of CSG. Similar results were obtained when M.Ab.G10 was used. Preincubation of platelets with 600 ng/ml CSA or CSG resulted in 60% and 30% increase in total protein kinase C activity, respectively, following the addition of ADP. In conclusion, this study has determined that preincubation of platelets with CSA or FK-506 (CSG, to a smaller extent) results in significant enhancement of ADP-induced platelet aggregation and secretion. The hyperaggregation and hypersecretion observed may be due to an enhanced expression of fibrinogen receptors on the platelet surface resulting from an increase in protein kinase C activity.
Cell Mol Biol Res 1993
PMID:Comparative investigation of the effects of the immunosuppressants cyclosporine A, cyclosporine G, and FK-506 on platelet activation. 750 91


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