Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:3.6.3.1 (Mg2+-ATPase)
1,484 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

In athyreotic dystrophy of the heart muscle properties both actin- and myosin-containing fibers protein components are shown to change. Changes in actin-containing filaments become apparent in a decrease in superprecipitation value of hybrid actomyosin consisting of athyreotic actin and myosin from normal myocardium. Disturbances in myosin structure result in a decrease of both, the value and rate of hybrid actomyosin superprecipitation consisting of athyreotic myosin and normal actin. The value of Mg2+-ATPase activity of hybrid actomyosins does not practically differ from that of normal actomyosin. Native athyreotic tropomyosin loses its ability to activate Mg2+-ATPase of purified actomyosin but its Ca2+ sensitivity, as well as its ability to increase the superprecipitation rate of normal actomyosin do not change. The obtained data suggest that a decrease in a tension value developed by bundles of glycerinated muscle fibers of athyreotic myocardium results from changes in the properties of both actin and myosin, while a reduction in the rate of fiber contraction is caused by disturbances of myosin properties and may be of native tropomyosin as well.
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PMID:[Structural-functional alterations in contractile proteins in athyreotic dystrophy of the myocardium]. 613 27

It has been possible to specifically label rabbit skeletal muscle actin at Lys-237 with 2,4-pentanedione, producing an enamine. This reaction can be reversed with hydroxylamine. The modification can be carried out with actin in either the G- or F-forms and does not affect polymerization-depolymerization. The modification does affect, however, the interaction of tropomyosin (Tm) with the modified F-actin. In the absence of Ca2+ and Mg2+ (mu = 0.12), Tm failed to bind to the modified F-actin whereas it did bind to unmodified F-actin (1 Tm:7 actins). Tm binding could be restored under these conditions by the addition of either troponin (Tn), Mg2+, or Mg2+ and Ca2+. Under certain conditions, Tm alone has been shown to inhibit actin-activated heavy meromyosin (HMM)-Mg2+-ATPase. This inhibition did not occur with the modified F-actin even though Tm was bound (approximately 1 Tm:7 actins). Even when Tn was added to this system (in the absence of Ca2+), no inhibition of ATPase could be observed. Thus, this modification appears to prevent F-actin X Tm from assuming the "blocking" inhibitory position (conformation). In addition, Tn appears to enhance the activation of heavy meromyosin-Mg2+-ATPase by the modified F-actin X Tm complex whether Ca2+ is present or not. This state may be analogous to the potentiated state (Murray, J. M., Knox, M. K., Trueblood, C. E., and Weber, A. (1982) Biochemistry 27, 906-915) seen with myosin subfragment 1-saturated actin at low ATP levels. Thus, using modified and unmodified F-actin, it is possible to produce three Tm X actin states: off (F-actin X Tm), on (modified F-actin X Tm), and "potentiated" (modified F-actin X Tm X Tn).
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PMID:Modification of Lys-237 on actin by 2,4-pentanedione. Alteration of the interaction of actin with tropomyosin. 614 49

Caldesmon, a major calmodulin- and actin-binding protein of smooth muscle (Sobue, K., Muramoto, Y., Fujita, M., and Kakiuchi, S. (1981) Proc. Natl. Acad. Sci. U. S. A. 78, 5652-5655), has been obtained in highly purified form from chicken gizzard by a modification of a previously published procedure (Ngai, P. K., Carruthers, C. A., and Walsh, M. P. (1984) Biochem. J. 218, 863-870) and was found to cause a significant inhibition of both superprecipitation and actin-activated myosin Mg2+-ATPase activity in a system reconstituted from the purified contractile and regulatory proteins without influencing the phosphorylation state of myosin. This inhibitory effect was seen both in the presence and absence of tropomyosin. A Ca2+-and calmodulin-dependent kinase which catalyzed phosphorylation of caldesmon was identified in chicken gizzard; this kinase is distinct from myosin light-chain kinase. Caldesmon prepared by calmodulin-Sepharose affinity chromatography was contaminated with caldesmon kinase activity and was unable to inhibit actomyosin ATPase activity or superprecipitation. Phosphatase activity capable of dephosphorylating caldesmon was also identified in smooth muscle. These results indicate that caldesmon can inhibit smooth muscle actomyosin ATPase activity in vitro, and this function may itself be subject to regulation by reversible phosphorylation of caldesmon.
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PMID:Inhibition of smooth muscle actin-activated myosin Mg2+-ATPase activity by caldesmon. 615 36

It was found that thin filaments from chicken gizzard muscle activate skeletal muscle myosin Mg2+-ATPase to a greater extent than does the complex of chicken gizzard actin and tropomyosin. The protein factor responsible for this additional activation has been now identified as the high Mr actin binding protein, filamin.
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PMID:Potentiation of actomyosin ATPase activity by filamin. 615 Aug 68

Under the influence of regular acceleration (5 g for 25 min during 15 days) Mg2+-ATPase activity of native and desensitized actomyosin of the myocardium and femurs of white rats increased. This was in correlation with increases in the rate of actomyosin superprecipitation (Vspp) and in the surface charge of macromolecules. The control animals showed a decrease in the inhibition of Mg2+-ATPase and Vspp of native actomyosin by tropomyosin-troponin. Ca2+ in a concentration of 10(-7) - 10(-4) M stimulated Mg2+-ATPase of native actomyosin of experimental animals by 50% only, but the maximum activation of Vspp was significantly higher than in the controls. It is assumed that these changes tend to increase the efficiency of the actomyosin system.
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PMID:[Effect of periodic gravitation overloads on the physico-chemical properties and Ca2+ reactivity of actomyosin of the myocardium and skeletal muscles of albino rats]. 615 Oct 16

alpha-Actinin purified from chicken gizzard smooth muscle was characterized in comparison with alpha-actinins from chicken striated muscles, or fast-skeletal muscle, slow-skeletal muscle, and cardiac muscle. The gizzard alpha-actinin molecule consisted of two apparently identical subunits with a molecular weight of 100,000 on SDS-polyacrylamide gel electrophoresis, as do striated-muscle alpha-actinins. Its isoelectric points in the presence of urea were similar to the striated-muscle counterparts. Despite these similarities, distinctive amino acid sequences between smooth-muscle alpha-actinin and striated-muscle alpha-actinins were revealed by peptide mapping using limited proteolysis in SDS. Gizzard alpha-actinin was immunologically distinguished from striated-muscle alpha-actinins. Gizzard alpha-actinin formed bundles of gizzard F-actin as well as of skeletal-muscle F-actin, but could not form any cross-bridges between adjacent actin filaments under conditions where skeletal-muscle alpha-actinin could. Temperature-dependent competition between gizzard alpha-actinin and tropomyosin on binding to gizzard thin filaments was demonstrated by electron microscopic observations. Gizzard alpha-actinin promoted Mg2+-ATPase activity of reconstituted skeletal actomyosin, gizzard acto-skeletal myosin, and gizzard actomyosin. This promoting effect was depressed by the addition of gizzard tropomyosin. These findings imply that, despite structural differences between gizzard and striated-muscle alpha-actinin molecules, they function similarly in vitro, and that gizzard alpha-actinin can interact not only with smooth-muscle actin (gamma- and beta-actin) but also with skeletal-muscle actin (alpha-actin).
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PMID:Molecular properties and functions in vitro of chicken smooth-muscle alpha-actinin in comparison with those of striated-muscle alpha-actinins. 621 60

On treatment with 10 mM EDTA at 30 degrees C, protein of 18,000 daltons was released from myofibrils, thin filaments and myosin B prepared from the smooth muscle of an ascidian, Halocynthia roretzi. This protein was purified from the EDTA extract of myofibrils by differential centrifugation, freeze-drying and gel-filtration. Based on its molecular weight, electrophoretic mobilities in the presence and absence of Ca2+ and other properties, it was identified as troponin C. By EDTA treatment, ascidian myosin B lost the Ca2+-sensitivity of Mg2+-ATPase, and EDTA-treated myosin B recovered the sensitivity by mixing with the EDTA extract of myosin B in the presence of Mg2+. Gel-electrophoretic patterns indicated that desensitization and resensitization of ascidian myosin B were accompanied by the removal and binding of troponin C. These results indicate that ascidian smooth muscle is regulated by a troponin-tropomyosin system, and desensitization induced by EDTA treatment is due to the removal of troponin C but not the release of the light chains of the myosin molecule. Based on these findings, we have established a simple method for the purification of troponin C from ascidian smooth muscle.
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PMID:Removal of troponin C and desensitization of myosin B from ascidian smooth muscle by treatment with ethylene diamine tetraacetate. 623 Dec 81

Antitropomyosin and anti-alpha-actinin monoclonal antibodies have been used to isolate two classes of microfilaments, i.e., tropomyosin-enriched and alpha-actinin-enriched microfilaments, respectively, from cultured chicken embryo fibroblasts. Electron microscopic studies of the isolated tropomyosin-enriched microfilaments showed periodic localization of tropomyosin along the microfilaments, with a 35-nm repeat. On the contrary, the isolated alpha-actinin-enriched microfilaments showed no obvious periodicity. Many individual alpha-actinin-enriched microfilaments with length greater than 1 micron (ranging from 1 to 10 microns) were aggregated by anti-alpha-actinin monoclonal antibodies. Both of the isolated microfilaments had the ability to activate the Mg2+-ATPase activity of skeletal muscle myosin, although different extents of activation were observed. These two classes of microfilaments also differed in their protein composition. Molar ratios of major identifiable proteins in the isolated microfilaments were alpha-actinin(dimer):actin(monomer):tropomyosin(dimer) = less than 0.02:8.06:1.00 for tropomyosin-enriched microfilaments and 0.44:13.91:1.00 for alpha-actinin-enriched microfilaments. By two-dimensional gel analysis of the isolated microfilaments, we have found seven spots which possess typical tropomyosin properties including pI 4.5, immunological cross-reaction, lack of proline and tryptophan, and heat stability. Pulse-chase experiments suggested that the assembly of microfilament-associated proteins, at least for alpha-actinin and tropomyosins, was coordinately regulated by the assembly of actin into microfilaments.
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PMID:Tropomyosin-enriched and alpha-actinin-enriched microfilaments isolated from chicken embryo fibroblasts by monoclonal antibodies. 653 70

1. Crayfish myosin B lost Ca2+-dependent regulation in superprecipitation upon addition of pure rabbit skeletal F-actin. 2. Actomyosin reconstituted from crayfish myosin and pure rabbit skeletal F-actin showed both Ca2+-dependent regulation in superprecipitation and Mg2+-ATPase activity upon addition of native tropomyosin prepared from crayfish or rabbit skeletal muscles. Also, superprecipitation of this actomyosin was induced by ITP without Ca2+-dependent regulation, as is the case in rabbit skeletal actomyosin. 3. Actomyosin reconstituted from crayfish native thin filament and crayfish or rabbit skeletal myosins showed Ca2+-dependent regulation. 4. These findings indicate that crayfish myosin is similar to rabbit skeletal myosin and different from chicken gizzard myosin in regulatory function.
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PMID:Crayfish myosin has no Ca2+-dependent regulation in actomyosin. 681 29

During development of the ascidian Halocynthia roretzi, the tadpole larva hatched from the tailbud embryo metamorphoses to the sessile adult with a body wall muscle. Although the adult body wall muscle is morphologically nonsarcomeric smooth muscle, it contains troponin complex consisting of three subunits (T, I, and C) as do vertebrate striated muscles. Different from vertebrate troponins, however, the smooth muscle troponin promotes actomyosin Mg2+-ATPase activity in the presence of high concentration of Ca2+, and this promoting property is attributable to troponin T. To address whether the embryonic/larval tail striated muscle and the adult smooth muscle utilize identical or different regulatory machinery, we cloned troponin T cDNAs from each cDNA library. The embryonic and the adult troponin Ts were encoded by distinct genes and shared only <60% identity with each other. Northern blotting and whole mount in situ hybridization revealed that these isoforms were specifically expressed in the embryonic/larval tail striated muscle and the adult smooth muscle, respectively. These results may imply that these isoforms regulate actin-myosin interaction in different manners. The adult troponin T under forced expression in mouse fibroblasts was unexpectedly located in the nuclei. However, a truncated protein with a deletion including a cluster of basic amino acids colocalized with tropomyosin on actin filaments. Thus, complex formation with troponin I and C immediately after the synthesis is likely to be essential for the protein to properly localize on the thin filaments.
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PMID:Distinct troponin T genes are expressed in embryonic/larval tail striated muscle and adult body wall smooth muscle of ascidian. 891 Mar 84


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