Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.4.24.27 (thermolysin)
 1,894 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We have observed that treatment of rabbit synovial fibroblasts with proteolytic enzymes can induce secretion of collagenase (EC 3.4.24.7) and plasminogen activator (EC 3.4.21.-). Cells treated for 2-24 hr with plasmin, trypsin, chymotrypsin, pancreatic elastase, papain, bromelain, thermolysin, or alpha-protease but not with thrombin or neuraminidase secreted detectable amounts of collagenase within 16-48 hr. Treatment of fibroblasts with trypsin also induced secretion of plasminogen activator. Proteases initiated secretion of collagenase (up to 20 units per 10(6) cells per 24 hr) only when treatment produced decreased cell adhesion. Collagenase production did not depend on continued presence of proteolytic activity or on subsequent cell adhesion, spreading, or proliferation. Routine subculturing with crude trypsin also induced collagenase secretion by cells. Secretion of collagenase was prevented and normal spreading was obtained if the trypsinized cells were placed into medium containing fetal calf serum. Soybean trypsin inhibitor, alpha(1)-antitrypsin, bovine serum albumin, collagen, and fibronectin did not inhibit collagenase production. Although proteases that induced collagenase secretion also removed surface glycoprotein, the kinetics of induction of cell protease secretion were different from those for removal of fibronectin. Physiological inducers of secretion of collagenase and plasminogen activator by cells have not been identified. These results suggest that extracellular proteases in conjunction with plasma proteins may govern protease secretion by cells.
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PMID:Proteases induce secretion of collagenase and plasminogen activator by fibroblasts. 20 72

P-selectin on platelets and endothelial cells and E-selectin on endothelial cells are leukocyte receptors that recognize lineage-specific carbohydrates on neutrophils and monocytes. The proposed ligands for these receptors contain the Le(x) core and sialic acid. Since other investigators have shown that both E-selectin and P-selectin bind to sialylated Le(x), we evaluated whether E-selectin and P-selectin recognize the same counter-receptor on leukocytes. The interaction of HL60 cells with Chinese hamster ovary (CHO) cells expressing P-selectin or E-selectin was studied. To determine whether a protein component is required in addition to sialyl Le(x) for either P-selectin or E-selectin recognition, HL60 cells or neutrophils were digested with proteases, including chymotrypsin, elastase, proteinase Glu-C, ficin, papain, or thermolysin. Cells treated with these proteases bound E-selectin but not P-selectin. Fucosidase or neuraminidase treatment of HL60 cells markedly decreased binding to both E-selectin- and P-selectin-expressing CHO cells. Growth of HL60 cells in tunicamycin inhibited the ability of these cells to support P-selectin-mediated binding and, to a lesser extent, E-selectin-mediated binding. Purified P-selectin inhibited CHO:P-selectin binding to HL60 cells, but incompletely inhibited CHO:E-selectin binding to HL60 cells. However, purified soluble E-selectin inhibited CHO:P-selectin and CHO:E-selectin binding to HL60 cells equivalently and completely. COS cells, unable to bind to E-selectin or P-selectin, bound E-selectin but not P-selectin upon transfection with alpha-1,3-fucosyltransferase or alpha-1,3/1,4-fucosyltransferase. Similarly, LEC 11 cells expressing sialyl Le(x) bound E-selectin- but not P-selectin-expressing CHO cells. Sambucus nigra lectin, specific for the sialyl-2,6 beta Gal/GalNAc linkage, inhibited P-selectin but not E-selectin binding to HL60 cells. Although sialic acid and Le(x) are components of the P-selectin ligand and the E-selectin ligand, these results indicate that the ligands are related, having overlapping specificities, but are structurally distinct. A protein component containing sialyl Le(x) in proximity to sialyl-2,6 beta Gal structures on the P-selectin ligand may contribute to its specificity for P-selectin.
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PMID:P-selectin and E-selectin. Distinct but overlapping leukocyte ligand specificities. 137 36

The low pH-induced fusion of influenza virus with intact erythrocyte plasma membranes is preceded by a delay time following pH reduction, that is itself pH- and temperature dependent. At 37 degrees C/pH 4.8, lipid mixing between virus and target membranes begins < 2 s after pH reduction, whereas at 4 degrees C/pH 4.8, fusion does not commence until > 10 min after pH reduction. We have found that within this time period at 4 degrees C, a population of virus acquires the capacity to subsequently undergo fusion with high efficiency at elevated temperatures and pH 7.4. Both the kinetics and the extent of this pH 7.4 fusion depend upon the time of pre-incubation at pH 4.8/4 degrees C. Incubation at pH 7.4/4 degrees C, following this pre-incubation does not result in fusion, but the capacity to fuse at pH 7.4/37 degrees C is retained for a time period exceeding 1 h. The longevity of this fusion committed state makes it amenable to biochemical and immunological analysis. We have shown that it is insensitive to dithiothreitol, neuraminidase and trypsin, but is incapacitated by thermolysin or protease K. We conclude that only the HA2 sub-unit of influenza haemagglutinin is a necessary protein component of later stages of the fusion pathway.
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PMID:A long-lived state for influenza virus-erythrocyte complexes committed to fusion at neutral pH. 139 18

Two-dimensional gel electrophoresis (2DGE) and image processing were used to quantify protein and carbohydrate heterogeneity in human plasma fibronectin (FN) and its enzymatically produced domains. After a 30 minute thermolysin digest of FN, the domains were identified in 2DGE by their known isoelectric points and molecular weights, which were compared to domain standards purified by hydroxyapatite, gel exclusion and heparin-Sepharose chromatography. Three individual species were observed in the cell binding domain which may correspond to the heterogeneity known to result from alternative splicings of the fibronectin gene. In addition, the carbohydrate heterogeneity in the gelatin binding domain was analyzed by 2DGE and isoelectric focusing (IEF) before and after treatment with N-glycanase and neuraminidase to remove selected carbohydrate moieties. Five individual species which differ in carbohydrate structure were observed. The results also indicate a carbohydrate dependent stabilization of the gelatin binding domain with respect to proteolytic digestion.
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PMID:Separation and characterization of fibronectin domains by two-dimensional electrophoresis. 209 3

Three monoclonal antibodies (mAbs), termed SN2, SN2a and SN2b, were used in the present work to study a human T-cell leukemia-associated cell surface glycoprotein, GP37. Strong specificity of mAbs SN2, SN2a and SN2b for T leukemia cells was demonstrated by radioimmunoassay and fluorescence-activated cell sorter (FACS) analysis. GP37 was not detected on normal human peripheral blood lymphocytes, purified normal T-cells, normal thymocytes nor normal bone marrow cells. Furthermore, GP37 was barely detectable on phytohemagglutinin (PHA)- and Concanavalin A (Con A)-activated T-cells. The results indicate clinical utility of these mAbs. Competitive binding experiments show that the epitopes recognized by SN2 and SN2a are sufficiently close to each other to allow complete reciprocal inhibition of binding whereas the epitopes recognized by SN2 and SN2b are less close to allow only partial reciprocal binding inhibition. The biochemical nature of antigenic determinants defined by these mAbs was studied by treating T leukemia cells with trypsin, chymotrypsin, thermolysin, neuraminidase and mixed glycosidases. The results suggest that the antigenic determinants defined by these mAbs all consist of the protein moiety of the glycoprotein GP37. No significant antigenic modulation was observed when T leukemia cells were reacted with SN2. In a sequential immunoprecipitation experiment, a 125I-labeled leukemia antigen preparation was first treated with a rabbit anti-T leukemia antiserum. The latter had been prepared by immunizing a rabbit with a partially purified human T leukemia antigen preparation and showed a good specificity for T leukemia cells. Subsequent treatment of the labeled antigen preparation with SN2 showed that SN2 antigen had been precleared. Thus, both mouse mAb SN2 and the rabbit anti-T leukemia antiserum react with the same GP37 molecule.
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PMID:Human T-cell leukemia-associated cell surface glycoprotein GP37: studies with three monoclonal antibodies and a rabbit antiserum. 348 64

F (fusion) and HANA (hemagglutinin and neuraminidase) glycoproteins of HVJ (Sendai virus) were purified and characterized. The NH2-terminal hydrophobic region of the F1 (larger) subunit of F (fusion)-glycoprotein seems to be required for the hemolytic and cell fusion-inducing activity of the virus for the following reasons. (1) Selective splitting off of a 2,500-3,500 dalton segment from the NH2-terminal region of F1 by chymotrypsin or thermolysin resulted in inactivation of the biological activities of HVJ. (2) At least a part of this region may be exposed to the surrounding medium, since it is preferentially iodinated and is easily split by aminopeptidase M, chymotrypsin, and thermolysin. Tryptic digestion, which does not remove the NH2-terminal region but produce nicking of F1 subunit to subfragments F1a (larger one) and F1b (smaller one), resulted in substantial structural changes evidenced by circular dichroism measurement and iodination by lactoperoxidase method. Trypsin-digested F seems to have the NH2-terminal hydrophobic region buried within hydrophobic interior of the protein (or in the lipid bilayers). Based on these and other results, we propose a hypothesis featuring direct interaction of the hydrophbic region with the lipid bilayers of the target-cell membrane as an important step in fusion reactions between the viral envelope and cell membranes.
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PMID:Viral proteins in cell fusion. 631 Aug 22

Proteolytic enzyme activity releasing sialo glycopeptides from 3H-labeled human erythrocyte ghosts was detected in cytotoxic (leukotoxic) culture supernatants from 9 of 12 Pasteurella haemolytica serotypes. Microcrystalline cellulose thin-layer chromatograms of radioactive water-soluble products showed the following two radioactive peaks: a high-mobility minor peak (Rf, 0.54 to 0.74), identified as sialic acid, and a low-mobility major peak (Rf, 0.18 to 0.21), partially characterized as a trichloroacetic acid-soluble, sialic acid-rich fragment with a molecular weight of greater than 3,500, not extractable by chloroform. The sialic acid content of this fragment after treatment with Clostridium perfringens neuraminidase was estimated to be 7.2 X 10(-2) mumol mg-1. The presence of neuraminidase as a separate activity in some culture supernatants was confirmed. It is considered to be responsible for the observed release of free sialic acid. Preliminary studies with the crude enzyme showed that it has a broad pH optimum around pH 7.0 and that activity is not affected by inhibitors of trypsin, chymotrypsin, thermolysin, thio and serine enzymes, nor by an inhibitor of neuraminidase, 2,3-dehydro-2-deoxy-N-acetylneuraminic acid. Activity was, however, inhibited by o-phenanthroline at a high concentration after prolonged treatment. The enzyme hydrolyzed glycophorin at a rate four times higher than the rate for casein. Free glycophorin inhibited the enzyme-induced release of radioactive products from 3H-labeled ghosts. It is speculated that the novel enzyme is a neutral protease, probably metal-dependent, with specificity for sialoglycopeptides. The possible relationship of this protease to the previously reported host species-specific leukotoxicity of P. haemolytica and its potential role in virulence is discussed.
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PMID:Proteolysis of sialoglycoprotein by Pasteurella haemolytica cytotoxic culture supernatant. 635 4

One of the earliest events in the adhesion of fibroblasts to a substratum is the recognition by the cells of macromolecular adhesive factors, such as fibronectin. This early event is followed by a complex series of cell alterations leading to adhesion and spreading. To identify cell surface components involved in the initial cell-fibronectin recognition step, we have employed an assay involving latex particles coated with radiolabelled plasma Fibronectin (Fn). In previous studies from this laboratory (Harper & Juliano , J cell biol 87 (1980) 755) [28], we demonstrated that Fn-mediated adhesion of CHO cells is temperature-dependent, cation-dependent and sensitive to cytoskeletal disrupting agents; by contrast, binding of 3H-Fn beads was unaffected by these factors, indicating that this process reflects binding and recognition events at the cell surface which are independent of cytoskeletal and metabolic activity. Biological specificity of 3H-Fn bead-to-cell binding was confirmed by the ability of anti-Fn antisera to completely block the process. To examine surface components which may mediate binding we treated Fn beads with purified glycosaminoglycans (GAGs) or glycolipids prior to incubation with cells. Among the GAGs tested, heparin, heparan sulfate and dermatan sulfate blocked bead binding in a dose-related fashion with heparin being most potent. The gangliosides GT1, and GM1, also inhibited bead binding. However, treatment of cells with neuraminidase had no effect on bead binding while subsequent analysis of treated cells by thin layer chromatography revealed a drastic reduction in the amount of GM3, the predominant CHO cell ganglioside. CHO cells were also incubated with a panel of proteolytic enzymes to study the possible role of cell surface proteins or glycoproteins in Fn bead binding. We found 3H-Fn bead binding to be quite sensitive to pretreatment with thermolysin, pronase, and papain but only moderately sensitive to treatment with trypsin. From our findings we suggest: (1) binding of Fn beads to CHO cells reflects an early step in the adhesion process; (2) glycolipids may block bead binding but are probably not the endogenous binding site for Fn; (3) protease sensitive components (glycoproteins or proteoglycans) may be more likely candidates as cell surface-binding sites for Fn.
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PMID:Interaction of fibronectin-coated beads with CHO cells. 637 25

A major allergen has been identified in an aqueous extract of the 'green nimitti' midge, Cladotanytarsus lewisi (Diptera: Chironomidae). Following chromatography on Sephadex G-100 allergenic activity, as assessed by skin ('prick') testing, eluted as two closely related peaks (pools I and II) at about 50% bed volume. When these pools were applied separately to columns of CM-cellulose, activity in each eluted with 0 . 05 M NaCl. Isoelectric focusing of the unfractionated allergen gave a single peak of activity at pI 4 . 3. By SDS--PAGE, biological activity in the whole 'green nimitti' extract and the material eluting from both pools I and II of the Sephadex G-100 column migrated to the same positions and were associated with a molecular size of 15,000--20,000 daltons. Skin test reactivity of the unfractionated material and the Sephadex G-100 pool I and II eluates were all destroyed following incubation with trypsin, chymotrypsin, thermolysin and neuraminidase. These experiments indicate that a major allergen derived from the 'green nimitti' midge, a cause of widespread and severe immediate-type allergy in the Sudan, is an acidic glycoprotein of 15,000--20,000 molecular weight.
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PMID:Widespread IgE-mediated hypersensitivity in the Sudan to the 'green nimitti' midge, Cladotanytarsus lewisi (Diptera: Chironomidae) II. Identification of a major allergen. 743 59

Statistically significant charge clusters (basic, acidic, or of mixed charge) in tertiary protein structures are identified by new methods from a large representative collection of protein structures. About 10% of protein structures show at least one charge cluster, mostly of mixed type involving about equally anionic and cationic residues. Positive charge clusters are very rare. Negative (or histidine-acidic) charge clusters often coordinate calcium, or magnesium or zinc ions [e.g., thermolysin (PDB code: 3tln), mannose-binding protein (2msb), aminopeptidase (1amp)]. Mixed-charge clusters are prominent at interchain contacts where they stabilize quaternary protein formation [e.g., glutathione S-transferase (2gst), catalase (8act), and fructose-1,6-bisphosphate aldolase (1fba)]. They are also involved in protein-protein interaction and in substrate binding. For example, the mixed-charge cluster of aspartate carbamoyl-transferase (8atc) envelops the aspartate carbonyl substrate in a flexible manner (alternating tense and relaxed states) where charge associations can vary from weak to strong. Other proteins with charge clusters include the P450 cytochrome family (BM-3, Terp, Cam), several flavocytochromes, neuraminidase, hemagglutinin, the photosynthetic reaction center, and annexin. In each case in Table 2 we discuss the possible role of the charge clusters with respect to protein structure and function.
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PMID:Clusters of charged residues in protein three-dimensional structures. 871 Aug 74


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