Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.4.21.7 (plasmin)
 9,023 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Pregnancy-associated plasma protein A (PAPP-A) has been obtained in an enriched state under mild conditions of purification involving cibacron blue dye-ligand chromatography, negative antibody-affinity chromatography and gel filtration. The product was a mixture of PAPP-A and alpha-2-macroglobulin (alpha 2M). The ability of these proteins to bind 125I-trypsin and 125I-plasmin was studied. In contrast to previous studies by others, there was no evidence that PAPP-A could bind either protease. It is pointed out that protease-inhibitory activity in samples of PAPP-A can be due to the presence of very small amounts of contaminating alpha 2M in the preparations of PAPP-A. In further experiments PAPP-A did not inhibit the complement-induced lysis of sensitized red cells. Finally, cyanogen bromide peptide mapping experiments failed to yield evidence of structural homologies between PAPP-A and alpha 2M.
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PMID:Pregnancy-associated plasma protein A: purification under mild conditions, peptide mapping and tests for possible interactions with trypsin, plasmin and complement. 620 4

Activated human blood platelets show characteristic globular structures on their surface. Aggregated platelets in blood plasma form contact zones with 40-50 nm spaces between the plasmalemmata. These spaces are bridged by filamentous structures (5,000 per microns 2). To investigate whether the globules or bridges observed are caused by fibrinogen, platelets were washed and treated first with thrombin (1 U thrombin/ml) in order to remove fibrinogen from platelet storage organelles and then with plasmin (0.5-2 U/ml) in order to dissolve remnants of fibrinogen from the platelet surface. Platelets treated in this way were resuspended in tyrode-albumin buffer solution (containing hirudin and prostaglandin E1). No storage organelles were revealed but the platelets reconstituted their discoid shape and the marginal bundle of microtubules. By representing the platelet glycocalix with alcian blue it was observed that the previously homogeneous surface coat was interdispersed with holes of 60-70 nm in diameter, approx. 900 per microns 2. Fibrinogen (8 mg/ml) was then added and the suspension was stirred for 3 minutes at 37 degrees C. The platelets again aggregated and formed contact zones in blood plasma as described above. In spaces of 40 to 50 nm width filamentous bridges similar in size, structure and number to those between aggregated platelets in blood plasma were observed. In both cases the bridges appeared to adhere with small rods into the plasmalemma. Bridges and rods can be easily stained with protein stabilizing agents. In contrast, glycocalix treated with alcian blue are weakly stained. The findings strongly indicate that fibrinogen is the mediator of this type of platelet contact in aggregates. The fibrinogen binding sites are situated to the plasmalemmal outer leaf let and not on the peripheral glycocalix.
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PMID:Ultrastructural studies on the binding sites of fibrinogen on platelet surface during aggregation. 623 44

Gelsolin is a widely distributed actin binding protein that regulates actin filament length. It exists in both an intracellular and an extracellular form that is derived from a single gene by alternative splicing. Both forms contain the six homologous domains that are responsible for function. Little is known regarding differences between the forms. We have used a combination of cysteine-specific modification with 4-vinylpyridine, HPLC peptide mapping methods, and mass spectrometry to analyze the disulfide structures of human plasma and cytoplasmic gelsolin. Of the five Cys residues in the human gelsolin sequence, all were present in the free thiol form in human cytoplasmic gelsolin, while only three of them were free thiols in the human plasma form. Cys residues 188 and 201 in domain 2 of plasma gelsolin were disulfide linked. Recombinant human plasma gelsolin that had been expressed intracellularly in Escherichia coli and as a secreted protein from Cos green monkey cells was also investigated. The E. coli product lacked the disulfide but could be converted to the plasma-like structure with mild oxidation while the mammalian product formed the correct disulfide prior to isolation. Structural differences were also detected by limited proteolysis with plasmin. The differences in proteolytic susceptibility were also due to perturbations in domain 2. These studies demonstrate that the intracellular and extracellular gelsolins are structurally distinct and suggest that at least some of the preparations of recombinant gelsolin that are being used to study structure/function may be improperly folded. The experiments also demonstrate a general method for the location of disulfide bonds in proteins.
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PMID:The plasma and cytoplasmic forms of human gelsolin differ in disulfide structure. 870 41