Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.1.21.1 (DNase)
 7,655 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

In the search for a functional role of cytoskeletal proteins in the mechanism(s) of stimulus-secretion coupling, we have previously demonstrated that the actomyosin system might be involved in the transport of cations across the plasma membrane of bovine adrenal chromaffin cells [(1986) J. Biol. Chem. 261, 5745-5750]. To establish whether actin and myosin might also be involved in later stages of the cellular response, we have examined the possible effects of various actin-specific reagents on the calcium-mediated secretion of catecholamines from digitonin-permeabilized cells. F-Actin-destabilizing agents, such as cytochalasin D or DNase 1, were found to promote Ca2+-stimulated (as well as basal) secretion. By contrast, stabilizers, like phalloidin, produced the opposite effect. It is concluded that stimulus-secretion coupling in chromaffin cells might require the reorganization of actin for modulating both ion transport across the plasma membrane and exocytotic secretion per se.
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PMID:Destabilization of actin filaments as a requirement for the secretion of catecholamines from permeabilized chromaffin cells. 353 77

A highly branched filament network is the principal structure in the periphery of detergent-extracted cytoskeletons of macrophages that have been spread on a surface and either freeze or critical point dried, and then rotary shadowed with platinum-carbon. This array of filaments completely fills lamellae extended from the cell and bifurcates to form 0.2-0.5 micron thick layers on the top and bottom of the cell body. Reaction of the macrophage cytoskeletons with anti-actin IgG and with anti-IgG bound to colloidal gold produces dense staining of these filaments, and incubation with myosin subfragment 1 uniformly decorates these filaments, identifying them as actin. 45% of the total cellular actin and approximately 70% of actin-binding protein remains in the detergent-insoluble cell residue. The soluble actin is not filamentous as determined by sedimentation analysis, the DNAase I inhibition assay, and electron microscopy, indicating that the cytoskeleton is not fragmented by detergent extraction. The spacing between the ramifications of the actin network is 94 +/- 47 nm and 118 +/- 72 nm in cytoskeletons prepared for electron microscopy by freeze drying and critical point drying, respectively. Free filament ends are rare, except for a few which project upward from the body of the network or which extend down to the substrate. Filaments of the network intersect predominantly at right angles to form either T-shaped and X-shaped overlaps having striking perpendicularity or else Y-shaped intersections composed of filaments intersecting at 120-130 degrees angles. The actin filament concentration in the lamellae is high, with an average value of 12.5 mg/ml. The concentration was much more uniform in freeze-dried preparations than in critical point-dried specimens, indicating that there is less collapse associated with the freezing technique. The orthogonal actin network of the macrophage cortical cytoplasm resembles actin gels made with actin-binding protein. Reaction of cell cytoskeletons and of an actin gel made with actin-binding protein with anti-actin-binding protein IgG and anti-IgG-coated gold beads resulted in the deposition of clusters of gold at points where filaments intersect and at the ends of filaments that may have been in contact with the membrane before its removal with detergent. In the actin gel made with actin-binding protein, 75% of actin-fiber intersections labeled, and the filament spacing between intersections is consistent with that predicted on theoretical grounds if each added actin-binding protein molecule cross-links two filaments to form an intersection in the gel.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:The architecture of actin filaments and the ultrastructural location of actin-binding protein in the periphery of lung macrophages. 374 63

The shape of an actin subunit has been derived from an improved 6 A map of the complex of rabbit skeletal muscle actin and bovine pancreatic DNase I obtained by X-ray crystallographic methods. The three-dimensional structure of DNase I determined independently at 2.5 A resolution was compared with the DNase I electron density in the actin:DNase map. The two structures are very similar at 6 A resolution thus leading to an unambiguous identification of actin as well as DNase I electron density. Furthermore the correct hand of the actin structure is determined from the DNase I atomic structure. The resolution of the actin structure was extended to 4.5 A by using a single heavy-atom derivative and the knowledge of the atomic coordinates of DNase I. The dimensions of an actin subunit are 67 A X 40 A X 37 A. It consists of a small and a large domain, the small domain containing the N terminus. Actin is an alpha,beta-protein with a beta-pleated sheet in each domain. These sheets are surrounded by several alpha-helices, comprising at least 40% of the structure. The phosphate peak of the adenine nucleotide is located between the two domains. The complex of actin and DNase I as found in solution (i.e., the actin:DNase I contacts which do not depend on crystal packing) was deduced from a comparison of monoclinic with orthorhombic crystals. Residues 44-46, 51, 52, 60-62 of DNase I are close to a loop region in the small domain of actin. At a distance of approximately 15 A there is a second contact in the large domain in which Glu13 of DNase I is involved. A possible binding region for myosin is discussed.
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PMID:Three-dimensional structure of the complex of actin and DNase I at 4.5 A resolution. 406 3

The contractile proteins actin and myosin have been isolated from the soluble phase of guinea-pig polymorphonuclear leucocytes and partially characterised. Two forms of actin have been identified, designated 'Mg-actin' and 'KCl-actin'. They have different polymerising properties but their propensity to form synthetic homologous and heterologous actomyosins and to inhibit DNAase-1 does not significantly differ. Both show beta and gamma isoelectric forms in focusing gels and the Mg-actin accounts for about 5% of the soluble-phase protein and te KCl-actin around 2%. Leucocyte myosin has been isolated by affinity chromatography on N6-ADP-Sepharose with a good enrichment of both Ca2+-ATPase and the ATPase activity measured in the absence of Ca2+ or Mg2+ and in the presence of EDTA. This protein, too, has the capacity to form synthetic homologous and hybrid actomyosins with enhancement of the basal Mg2+-ATPase activity. The ratio of actin to myosin in the leucocyte calculated on a molar basis is well in excess of 100, a figure consistent with the findings from other non-muscle cells.
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PMID:The isolation and characterisation of guinea-pig polymorphonuclear leucocyte actin and myosin. 610 49

A low-molecular-weight protein, isolated from bovine brain, inhibits the actin-stimulated Mg-ATPase activity of myosin from striated muscle. This inhibition is probably related to its ability to cause actin to revert from its polymerized to its depolymerized state and to prevent the polymerization of actin. Its effect on the polymeric state of the actin has been demonstrated by viscosity studies. DNase inhibition assay, and electron microscopy. Heavy meromyosin can overcome the effect of the brain protein and stimulate the polymerization of actin. The inhibition of ATPase activity is in part dependent upon the relative amounts of brain protein, actin, and myosin. The apparent molecular weight of the brain protein is approximately 20,000 daltons. It appears to be a heat-labile glycoprotein containing 5-6% carbohydrate.
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PMID:Actin-stimulated myosin Mg2+-ATPase inhibition by brain protein. 613 41

Spermatocytes of the crane-fly, Nephrotoma suturalis, were attached to electron microscope grids and then sheared by applying centrifugal force. Transmission electron microscopy of exposed regions of the cell cortex revealed networks containing arrays of filamentous structures. Networks were present in sheared spermatocytes at all stages of meiosis. The networks of dividing spermatocytes (meta- through telophase) were denser and appeared to contain more aggregated material then networks of prophase cells. The appearance of networks in spermatocytes resembled actin-containing networks of sheared and detergent-extracted human erythrocytes. Networks treated with myosin subfragment 1 under conditions in which muscle F-actin was clearly decorated were not distinguishable from those of untreated cells. Exposure to deoxyribonuclease-1 caused the disruption of networks in sheared spermatocytes as well as in erythrocytes. The results of deoxyribonuclease experiments are interpreted as an indication that actin is a component of the cell cortex in crane-fly spermatocytes.
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PMID:Centrifugation shearing exposes filamentous networks in cortical regions of crane-fly spermatocytes. 621 61

During attempts to isolate bovine sperm actin, persistent low molecular weight proteinaceous (LMWP) contaminants were found. A LMWP fraction was prepared by gel filtration chromatography on Sephadex G150. The LMWP was found in extracts of washed bovine ejaculated spermatozoa and in clarified bovine seminal plasma. It was substantially reduced in amount in bovine epididymal spermatozoa, indicating that it originated from secondary sex gland secretions. The LMWP inhibited rabbit muscle actin-stimulated myosin adenosine triphosphatase (actin-myosin ATPase) activity. The LMWP:actin ratio for 50% inhibition of actin-myosin ATPase was 2.6 +/- 0.12 mg LMWP per mg actin. The LMWP interfered with actin inhibition of deoxyribonuclease, indicating that LMWP interacted with actin. The LMWP from seminal plasma had an estimated molecular weight of 8300 and consisted of several acidic components. It had negligible protease activity and its inhibition of actin-myosin ATPase was independent of divalent cations. The LMWP appears to readily aggregate with itself and other proteins, which may be related to its physiological role in semen.
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PMID:A bovine seminal plasma inhibitor of actin-stimulated myosin adenosine triphosphatase. 622 26

Gel filtration with 1% agarose (Bio-Gel A-150m) separates polyribosomes bound to microsomal membranes from 'free' polyribosomes when these fractions are prepared by standard centrifugal techniques. However, when polyribosomes contained in an unfractionated postmitochondrial supernatant are run on an identical column, over 90% of the total polyribosomes are present as aggregates, designated 'membrane-cytomatrix', which are eluted in the column void volume. Polyribosomes are not released from these aggregates on removal of microsomal phospholipids by treatment of postmitochondrial supernatant with 1% Triton X-100, a neutral detergent. The aggregates are disrupted by the usual ultracentrifugation techniques used in subcellular fractionation. After treatment of membrane-cytomatrix with Triton X-100 to remove phospholipids and membrane proteins, 58% of the polyribosomes still remain associated with protein-containing complexes in the form of a cytomatrix and are not 'free'. Preparations of both membrane-cytomatrix and cytomatrix are capable of sustained protein synthesis. Sodium dodecyl sulphate/polyacrylamide-gel electrophoresis revealed that the cytoskeletal proteins actin and myosin are present in the cytomatrix. Incubation of cytomatrix preparations with the actin-depolymerizing agent deoxyribonuclease I caused release of the polyribosomes. Polyribosome release by deoxyribonuclease I was prevented by prior incubation with phalloidin, which is known to stabilize F-actin. Thus polyribosomes are associated with cytoskeletal elements in rat liver, and this association is dependent on polymeric forms of actin.
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PMID:Preparation and properties of a complex from rat liver of polyribosomes with components of the cytoskeleton. 622 26

A quantitative assessment of the distribution and state of microfilament-related proteins in the heterocellular fundic gastric epithelium was carried out. Actin content, as determined by the DNAase inhibition assay, ranged from 29 to 42 micrograms/mg of tissue protein, depending upon the tissue source. About 60% of the total actin existed in fresh tissue in the polymeric form (F-actin). The distribution of fluorescent-labelled phallicidin demonstrated that F-actin was concentrated predominantly in the acid-secreting oxyntic cells. The patterns of distribution corresponded to the location of the numerous elongated apical surface microvilli seen within oxyntic cell canaliculi. In the isolated apical membrane, actin represented about 10% of the total protein and was present entirely as F-actin. After mild treatment of membranes with Triton X-100, filaments could be readily visualized by negative staining. More extensive Triton X-100 extraction solubilized intrinsic membrane protein and yielded an insoluble residue highly enriched in actin and containing several additional polypeptides. Homogenization and fractionation of the gastric epithelium in low ionic strength media led to the depolymerization of a significant proportion of the tissue actin which was recovered in the homogenate supernatant. When purified by DNAase affinity chromatography, this gastric actin displayed structural and functional properties similar to muscle actin. Incubation of the homogenate supernatant in KCl-Mg2+ induced the formation of actin-rich gels. The gels contained myosin as well as several other peptides that may be actin-binding proteins.
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PMID:Actin and associated proteins in gastric epithelial cells. 622 58

Using affinity chromatography on DNAase I-Sepharose, an actin-like protein was isolated from rat liver mitochondria and purified 60-fold. SDS electrophoresis in polyacrylamide gel revealed that the protein migrated with muscle actin and thus had the molecular weight of 42 000 Da. Evidence for the actin-like nature of the mitochondrial protein could be obtained from the fact that the protein inhibited the activity of pancreatic DNAase I which, similar to the smooth muscle protein, was less conspicuous than that of its muscle counterpart. Unlike striated muscle actin but similar to the smooth muscle protein, the mitochondrial actin weakly stimulated the Mg-ATPase activity of rabbit skeletal muscle myosin. After manyfold washing of the mitochondria with isotonic isolation media, the content of the actin-like protein remained unchanged, which indirectly points to the presence of insignificant cytoplasmic actin contaminations. During isoelectrofocusing, the mitochondrial actin-like protein yielded two forms, i. e., beta- and gamma-isoactins, whose ratio was 8:1. The pI values for the beta- and gamma-isoforms were 5.52 and 5.59, respectively. The identical position of the absorption spectra (260 nm) and fluorescence excitation spectra (around 280 nm) maxima of the actin-like protein and smooth and skeletal muscle actins testify to their homology.
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PMID:[Isolation and characteristics of actin-like proteins in liver mitochondria]. 624 Sep 91


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