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:3.6.1.3 (ATPase)
65,361 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

1. Microsomes were isolated from rabbit fast-twitch and slow-twitch muscle and were separated into heavy and light fractions by centrifugation in a linear (0.3-2m) sucrose density gradient. The membrane origin of microsomal vesicles was investigated by studying biochemical markers of the sarcoplasmic-reticulum membranes and of surface and T-tubular membranes, as well as their freeze-fracture properties. 2. Polyacrylamide-gel electrophoresis showed differences in the Ca(2+)-dependent ATPase/calsequestrin ratio between heavy and light fractions, which were apparently consistent with their respective origin from cisternal and longitudinal sarcoplasmic reticulum, as well as unrelated differences, such as peptides specific to slow-muscle microsomes (mol.wts. 76000, 60000, 56000 and 45000). 3. Freeze-fracture electron microscopy of muscle microsomes demonstrated that vesicles truly derived from the sarcoplasmic reticulum, with an average density of 9nm particles on the concave face of about 3000/mum(2) for both fast and slow muscle, were admixed with vesicles with particle densities below 1000/mum(2). 4. As determined in the light fractions, the sarcoplasmic-reticulum vesicles accounted for 84% and 57% of the total number of microsomal vesicles, for fast and slow muscle respectively. These values agreed closely with the percentage values of Ca(2+)-dependent ATPase protein obtained by gel densitometry. 5. The T-tubular origin of vesicles with a smooth concave fracture face in slow-muscle microsomes is supported by their relative high content in total phospholipid and cholesterol, compared with the microsomes of fast muscle, and by other correlative data, such as the presence of (Na(+)+K(+))-dependent ATPase activity and of low amounts of Na(+)-dependent membrane phosphorylation. 6. Among intrinsic sarcoplasmic-reticulum membrane proteins, a proteolipid of mol.wt. 12000 is shown to be identical in the microsomes of both fast and slow muscle and the Ca(2+)-dependent ATPase to be antigenically and catalytically different, though electrophoretically homogeneous. 7. Basal Mg(2+)-activated ATPase activity was found to be high in light microsomes from slow muscle, but its identification with an enzyme different from the Ca(2+)-dependent ATPase is still not conclusive. 8. Enzyme proteins that are suggested to be specific to slow-muscle longitudinal sarcoplasmic reticulum are the flavoprotein NADH:cytochrome b(5) reductase (mol.wt. 32000), cytochrome b(5) (mol.wt. 17000) and the stearoyl-CoA desaturase, though essentially by criteria of plausibility.
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PMID:Biochemical heterogeneity of skeletal-muscle microsomal membranes. Membrane origin, membrane specificity and fibre types. 628 27

Gel filtration of (Na+ + K+)-ATPase (ATP phosphohydrolase, EC 3.6.1.8) solubilized in octaethyleneglycol dodecylmonother ( C12E8 ) has been performed under conditions where active (alpha beta)2 dimers (Mr 265000) are obtained, and under conditions where dissociation into alpha beta monomers occurs without appreciable loss of activity. It is shown that the alpha beta monomers aggregate with time to form (alpha beta)2 dimers at low detergent concentrations with no change in enzymatic activity. At high detergent concentrations the aggregation is much slower, but the enzymatic activity is lost rapidly. Polyacrylamide gel electrophoresis in the presence of C12E8 also suggest that high concentrations of detergent dissociate the (alpha beta)2 dimer into smaller particles, and conditions for gel electrophoresis are described. The inactivating effect of C12E8 at high C12E8 /protein ratios can be related to a delipidation of the enzyme, with about 0.19 mg phospholipid required per mg protein for optimal activity. The experiments suggest that the solubilized (Na+ + K+)-ATPase can be disrupted into particles containing only one alpha-chain and one or two beta-chains without irreversible loss of activity, and that the stable form of the enzyme is an (alpha beta)2 dimer.
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PMID:The distribution of C12E8-solubilized oligomers of the (Na+ + K+)-ATPase. 632 42

The purpose of the present study was to compare the ATPase activities of cardiac SR in two species in which the different intrinsic myocardial contractility can only partially be explained by the different properties of cardiac myosins. In cardiac SR isolated from rat heart, the total ATPase activity was 1512.5 +/- 23.3 nmol Pi/mg protein/min, nearly four times as high as in dog cardiac SR (408.8 +/- 28.9 nmol Pi/mg protein/min). The Ca2+-activated ATPase in rat cardiac SR represented only 23.8% of the total ATPase activity, while in dog cardiac SR it was approximately 50% of the total. Thus, the specific Ca2+-activated ATPase was nearly two times higher in the cardiac SR of the rat than in that of the dog. This higher rate of ATP hydrolysis in rat cardiac SR may be, at least in part, responsible for the increased intensity and shorter duration of the active state in the rat myocardium. Polyacrylamide gel electrophoresis of SR showed that the relative amount of Ca2+-pump protein was two times higher in dog heart, similar to the percentage of Ca2+-activated ATPase activity. At the same time, the specific Ca2+-activated ATPase activity and the relative amount of Ca2+ pump protein in both the rat and dog cardiac SR were inversely related.
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PMID:Comparison of ATPase activity of cardiac sarcoplasmic reticulum fraction from rat and dog. 645 35

1. Two membrane fractions were separated from rabbit white muscle SR by discontinuous sucrose gradient. 2. Both crude and membrane fractions were shown to contain AChE, Ca2+-stimulated and Ca2+- independent ATPase activities. 3. 1% W/V Triton X-100 solubilized most of the AChE and Ca2+-stimulated ATPase but the Ca2+- independent ATPase was poorly solubilized. 4. AChE was sensitive to BW284c51, non-sensitive to ethopropazine and presented inhibition by excess of the substrate, ATCh. 5. Polyacrylamide gel electrophoresis from Triton-treated crude SR revealed several bands of AChE and ATPase activities. 6. SDS-gel electrophoresis from crude SR showed two polypeptides specifically labelled with [3H]DFP.
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PMID:Acetylcholinesterase from sarcoplasmic reticulum of white muscle. 710 63

Sarcoplasmic reticulum (SR) from rabbit back muscles can be readily subfractionated into two morphologically and compositionally different vesicular populations, SRH (heavy) and SRL (light) derived from terminal cisternae and longitudinal SR, respectively. Polyacrylamide gels indicate that SRH contains most of the calsequestrin. Quantitation of freeze-fractured isolated preparations reveals that, while differences in vesicular dimensions are seen in SRH and SRL, the intramembrane particle (Ca2+ ATPase) density is identical. Phospholipid headgroup composition is the same in SRH and SRL, but fatty acyl moieties show significant differences in the ratio of saturated to unsaturated phospholipids in the two fractions. The vesicular dimensions of the purified Ca2+-ATPases, SRHP and SRLP, from the two fractions are identical, but the freeze-fracture particle density is higher in the SRLP fraction. The phospholipid composition remains similar after purification, but the differences in phospholipid fatty acyl composition of the preparations are maintained. SRH and SRHP contain almost twice as much of the unsaturated species as compared to SRL and SRLP. Differences in intramembrane particle density in purified fractions, thermotropic segregation of particles in freeze-fractured purified fractions, as well as differences in turnover of the acyl phosphate, appear to reflect the differences in fatty acyl chain composition of the two SR fractions and provide evidence of microheterogeneity in lipid-protein environment of the SR.
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PMID:Evidence for membrane microheterogeneity in the sarcoplasmic reticulum of fast twitch skeletal muscle. 711 5

A newly-identified muscle protease which degraded myosin, alpha-actinin, and actin, and removed the Ca-sensitivity of the ATPase activity of myofibrils was purified from rabbit skeletal muscle by ammonium sulfate fractionation, Sephadex G-75 chromatography, P-cellulose chromatography, Sephadex G-75 rechromatography, and Ultrogel AcA 54 chromatography. Polyacrylamide gel electrophoresis showed that the enzyme thus obtained was almost homogeneous. The molecular weight of the enzyme was found to be 24,000 by gel filtration on Sephadex G-75. The optimum pH for the Ca-sensitivity-removing activity was pH 7.0, and that for the activity to degrade myosin was pH 4.1. The enzyme was stable at pH 4.5--6.5. It was strongly inhibited by iodoacetate, leupeptin, and antipain, but not by pepstatin or phenylmethane sulfonyl fluoride. EDTA was essential for the activity of the enzyme. The enzyme did not split alpha-N-benzoyl-DL-arginine-beta-naphthylamide. Since these properties resemble those of cathepsin L isolated from rat liver lysosomes, the enzyme was regarded as muscle cathepsin L.
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PMID:Purification and some properties of a myofibrillar protein-degrading protease, cathepsin L, from rabbit skeletal muscle. 739 Sep 82

A cyanobacterial sulfur-regulated gene (cysR), which encodes a protein with similarity to the Crp family of prokaryotic regulatory proteins, has recently been isolated and characterized. Polyacrylamide gel electrophoresis of periplasmic protein extracts reveals that a cysR mutant fails to synthesize a 36-kDa polypeptide that is normally induced in wild-type cells that have been grown under sulfur-deficient conditions. The amino-terminal sequence of this protein was obtained, and a synthetic oligonucleotide was used to isolated a clone containing a 1.9-kb NruI-KpnI fragment from a Synechococcus sp. strain PCC 7942 genomic library. RNA blot analysis indicates that this fragment encodes a transcript that is detectable in wild-type but not cysR mutant cells that have been starved for sulfur. DNA blot analysis revealed that the 1.9-kb NruI-KpnI fragment is contained within the Ba4 BamHI fragment of the endogenous 50-kb plasmid pANL. RNA blot studies indicate that the accumulation of a large number of pANL transcripts is regulated by sulfur levels and CysR. DNA sequence analysis confirmed that the gene encoding the sulfur-regulated 36-kDa periplasmic protein is encoded on the Ba4 fragment of pANL. The sequence of the 36-kDa protein displays sequence similarity to the enzyme catalase, and two downstream proteins exhibit 25 and 62% identity to a subunit of a P-type ATPase complex involved in Mg2+ transport and a chromate resistance determinant, respectively. Surprisingly, a strain in which the putative chromate resistance gene was interrupted by a drug resistance marker exhibited increased resistance to chromate when grown in media containing low sulfate concentrations. The possible role of this protein in the acclimation of cyanobacteria to conditions of low sulfur availability is discussed.
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PMID:Genes encoded on a cyanobacterial plasmid are transcriptionally regulated by sulfur availability and CysR. 753 34

We have studied the properties of rabbit skeletal troponin C (TnC) fully acetylated at its lysine residues (AcTnC). Acetylation causes a decrease in thermal stability of both domains of TnC in the absence of Ca2+. At 25 degrees C, the acetylated C-terminal domain of TnC is almost completely unfolded and the melting temperature of the N-terminal domain monitored by far-UV circular dichroism is decreased by 16.3 degrees C. In the presence of 1 mM CaCl2, no cooperative unfolding can be detected up to 90 degrees C for either TnC or AcTnC. At 25 degrees C, CD spectra show that AcTnC has a slightly lower alpha-helix content in the absence of Ca2+, but higher in the presence of Ca2+ as compared to unmodified TnC. Acetylation causes a 3.5-fold increase in affinity for Ca2+ at the low-affinity sites and a 2-fold decrease at the high-affinity sites. Polyacrylamide gel electrophoresis under nondissociating conditions (no SDS, no urea, pH 8.6) indicates that acetylation has little effect on the apparent affinity of TnC for troponin I; however, the binding of the acetylated peptides corresponding to the N-terminal domain of TnC to troponin I is significantly stronger than that of the unmodified peptides. Troponin T binding to AcTnC is significantly enhanced, the altered properties of the N-terminal domain being predominantly responsible for the increase. Titration of the ATPase activity of TnC-depleted myofibrils with AcTnC or native TnC indicates that acetylation increases TnC's affinity for myofibrils in the presence of Ca2+ approximately 6 times; at saturation the ATPase activity is the same for the two forms of TnC. The Ca2+ dependence of the ATPase activity of myofibrils containing AcTnC is shifted to lower Ca2+ concentrations, consistent with the higher Ca2+ affinity of AcTnC at the low-affinity sites. These data indicate that positively charged lysine side chains, especially those located in the N-terminal domain, modulate TnC's structural stability and interactions with Ca2+ and other troponin components.
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PMID:Properties of troponin C acetylated at lysine residues. 754 22

A fraction containing plasma membrane-enriched vesicles has been prepared from Tritrichomonas foetus. Cells were ruptured using a Potter type homogenizer, under well controlled conditions, and membranes were isolated by differential centrifugation and in discontinuous sucrose gradient. This fraction was enriched 8 and 10-fold in the plasma membrane marker enzymes 5'-nucleotidase and (Na+ + K+)-dependent, ouabain-sensitive ATPase, respectively. Determination of Glucose-6-phosphatase and NADPH cytochrome c reductase activities in this fraction, indicates a minimal contamination with endoplasmic reticulum membranes. Analysis by Sodium Dodecyl Sulfate-Polyacrylamide (SDS-PAGE) gradient gel showed that the plasma membrane fraction contains several proteins with major bands corresponding to apparent molecular weights of 48, 45, 39, 37, 32, 30, 27, 23, 20, 19, 17, and 15 kDa.
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PMID:Isolation and biochemical characterization of the plasma membrane of Tritrichomonas foetus. 865 56

This study examined the effects of 6 weeks of treatment with the beta(2)-adrenoceptor agonist, clenbuterol, on the soleus muscle of adult female Sprague-Dawley rats. Animals (4 months old) were divided into two groups: clenbuterol treated (CL, n = 7) (2 mg.kg-1 body mass injected subcutaneously every other day), and control (CON, n = 7) (injected with isotonic saline). Post-treatment body weights were approximately 5% greater in the CL group compared to CON (P < 0.05). Polyacrylamide gel electrophoresis (SDS-PAGE) of soleus myofibrillar protein indicated a clenbuterol-induced decrease (P < 0.05) in the relative percentage of type I myosin heavy chain (MHC) with a concomitant increase (P < 0.05) in type IIdx MHC, while the proportion of type IIa MHC was unaffected. ATPase fiber typing revealed increases (P < 0.05) in the proportion of type II fibers expressed both as a percentage of total fiber number and total cross-sectional area (CSA). Finally, mean type II fiber CSA was approximately 25% greater (P < 0.05) in the CL groups as compared to the CON group. These data indicate that clenbuterol treatment results in alterations in the MHC phenotype and an increased proportion of type II fiber CSA in the soleus of adult rats. These observations were due to an increase in the total number of type II fibers, as well as hypertrophy of these fibers. Thus, the relative increase in the number of histochemically determined type II fibers and the emergence of the normally unexpressed type IIdx MHC isoform in the soleus suggest a clenbuterol-induced transition of muscle fiber phenotype as well as selective hypertrophy of the type II fibers.
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PMID:Clenbuterol-induced fiber type transition in the soleus of adult rats. 895 85


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