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  • 1
    ISSN: 1749-6632
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Natural Sciences in General
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    Biochemistry 32 (1993), S. 4975-4978 
    ISSN: 1520-4995
    Source: ACS Legacy Archives
    Topics: Biology , Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: Calmodulin-dependent cyclic nucleotide phosphodiesterase (CaMPDE) is one of the key enzymes involved in the complex interaction between the cyclic nucleotide and Ca2+ second-messenger systems. CaMPDE exists as tissue-specific isozymes, and initially these isozymes were designated according to their respective subunit molecular mass. A variety of pharmacological agents have been used to inhibit CaMPDE, and this inhibition occurs mostly via Ca2+-dependent association with the proteins. We have examined the effect of dihydropyridine Ca2+-channel blockers felodipine and nicardipine on CaMPDE. The results suggest that the 63-kDa (PDE 1B1) and 60-kDa (PDE 1A2) CaMPDE isozymes are inhibited by felodipine and nicardipine by partial competitive inhibition and that these two Ca2+ antagonists appear to counteract each other. This study further demonstrates the existence of a specific site, distinct from the active site on CaMPDE, that exhibits high-affinity binding of these drugs. Felodipine and nicardipine have similar affinities for 60-kDa CaMPDE isozymes but bring about different levels of enzyme inhibition, suggesting the possibility of designing specific drugs that can protect the enzyme from inhibition by dihydropyridine Ca2+-channel blockers.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1573-4919
    Keywords: myristoylation ; myristoyltransferase ; myristoyl CoA ; inhibition ; activation ; purification
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract Myristoyl CoA:protein N-myristoyltransferase catalyzes the addition of myristate to the amino-terminal glycine residue of a number of eukaryotic proteins.Escherichia coli transformed with human NMT expression construct produced high levels of N-myristoyltransferase. Using the combination of ammonium sulfate precipitation, chromatography on SP-Sepharose fast flow and fast protein liquid chromatography on Mono-S, the enzyme was purified more than 100 fold with 40% yield. The hNMT fusion protein exhibited an apparent molecular weight of 53 kDa on SDS-polyacrylamide gel electrophoresis. Upon cleavage by the Enterokinase [(Asp)4-Lys], the hNMT exhibited an apparent molecular mass of 49 kDa without loss of catalytic activity. The hNMT activity could be greatly activated severalfold with the use of Tris, SDS, ethanol and acetonitrile. The catalytic activity of hNMT was potently inhibited in a concentration dependent manner by NIP711 a bovine brain NMT inhibitory protein with a half maximal inhibition of 31.0 nM. TheE. coli expressed hNMT was homogeneous and showed enzyme activity.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1573-4919
    Keywords: Crystals ; X-ray ; Calcineurin A ; Calcineurin B ; Protein Phosphatase ; PP2B
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract Calcineurin is a serine/threonine protein phosphatase which catalyzes the hydrolysis of both phosphoseryl/phosphothreonyl and phosphotyrosyl proteins as well as low molecular weight compounds such as p-nitrophenyl phosphate. It is a hetero-dimeric protein consisting of a 60 kDa A chain and 19 kDa B chain. Calcineurin A is organized into functionally distinct domains such as a catalytic domain, a calcineurin B binding domain, a calmodulin-binding domain, and an inhibitory domain. Calcineurin B has four EF-hand calcium binding domains with a secondary structure that is homologous to calmodulin but its metal binding properties are more similar to troponin-C. The N-terminal myristoyl group of calcineurin B might play a role in the interaction between subunits A and B during phosphorylation/dephosphorylation processes. Crystals of size 0.125×0.07×0.03 mm and 0.7×0.03×0.02 mm have been obtained for calcineurin and the A subunit respectively. Crystals of calcineurin show strong diffraction to 5.3 Å and weak diffraction to 3.0 Å on rotating anode operated at 50 kV and 100 mA. Further work is in progress to improve the X-ray diffraction quality of these crystals and to obtain well diffracting crystals of calcineurin B.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1573-4919
    Keywords: calmodulin ; calmodulin-binding protein ; calmodulin-dependent protein kinase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract A high molecular weight calmodulin-binding protein (HMW CaMBP) from bovine heart cytosolic fraction was purified to apparent homogeneity. A novel CaM-dependent protein kinase was originally discovered when the total CaM-binding protein fraction from cardiac muscle was loaded on a gel filtration column. The CaM-dependent protein kinase was shown by gel filtration chromatography to have an apparent molecular mass of 36,000 daltons. The CaM-dependent protein kinase has been highly purified by sequential chromatography on DEAE-Sepharose C1 6B (to remove calmodulin), CaM-Sepharose 4B, phosphocellulose, Sepharose 6B gel filtration and Mono S column chromatographies. The highly purified protein kinase stoichiometrically phosphorylated the HMW CaMBP in a Ca2+/CaM-dependent manner. The phosphorylation resulted in the maximal incorporation of 1 mol of phosphate/mol of the HMW CaMBP. The distinct substrate specificity of this protein kinase indicates that it is not related to the known protein kinases (I, II, III, IV and V) that have been already characterized, therefore we would like to designate this novel kinase as a CaM-dependent protein kinase V1.
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 1573-4919
    Keywords: myristoyltransferase ; myristoyl-CoA ; lipid modification ; purification ; expression
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract Myristoylation refers to the co-translational addition of a myristoyl group to an amino-terminal glycine residue of a protein by an ubiquitously distributed enzyme myristoyl-CoA:protein N-myristoyltransferase (NMT, EC 2.3.1.97). This review describes the basic enzymology, molecular cloning and regulation of NMT activity in various pathophysiological processes such as colon cancer and diabetes.
    Type of Medium: Electronic Resource
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  • 8
    ISSN: 1573-4919
    Keywords: N-myristoyltransferase ; NIP71 ; mixed inhibition ; lipid
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract N-Myristoyl-CoA:protein N-myristoyltransferase (NMT) is the enzyme that catalyses the transfer of myristate from myristoyl-CoA to the N-terminal glycine of protein substrates. NMT was highly purified from bovine brain by procedures involving sequential column chromatography on DEAE-Sepharose CL-6B, phosphocellulose, hydroxylapatite, and mono S and mono Q f.p.l.c.. The highly purified NMT (termed NMT·II) possessed high specific activity with peptide substrates derived from the N-terminal sequences of the cAMP-dependent protein kinase and pp60src (29,800 and 47,600 pmol N-myristoylpeptide formed/min/mg, respectively), intermediate activity with a peptide based on the N-terminal sequence of a viral structural protein (μl) (M2; 17,300 pmol N-myristoylpeptide formed/min/mg) and very low activity with a peptide derived from the N-terminal sequence ofmyristoylatedalanine-richC-kinasesubstrate (MARCKS; 1500 pmol myristoylpeptide formed/min/mg). An NMT protein inhibitor (NIP71) isolated from the particulate fraction of bovine brain (King MJ and Sharma RK: Biochem J 291∶635-639, 1993) potently inhibited highly purified NMT activity (IC50 23.7 nM). A minor NMT activity (NMT·PU; 30% total NMT activity), which failed to bind to phosphocellulose, was insensitive to NIP71 inhibition. Inhibition of NMT was observed to be via mixed inhibition with respect to both the myristoyl-CoA and peptide substrates with NIP71 having an apparent higher affinity for NMT than the NMT·myristoyl·CoA complex. Inhibition by NIP71 at subsaturating concentrations of myristolyl-CoA and peptide resulted in a sigmoidal pattern of inhibition indicating that bovine brain possesses a potent and delicate on/off switch to control NMT activity.
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  • 9
    ISSN: 1573-4919
    Keywords: covalent modification ; myristoyl CoA ; myristate ; protein myristoylation ; N-myristoyltransferase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract Myristoyl CoA:Protein N-myristoyltransferase (NMT) is the enzyme which catalyses the covalent transfer of myristate from myristoyl CoA to the amino-terminal glycine residue of protein substrates. Although NMT is ubiquitous in eukaryotic cells, the enzyme levels and cellular distribution vary among tissues. In this article, we describe the properties of mammalian NMT(s) with reference to subcellular distribution, molecular weights, substrate specificity and the possible involvement of NMT in pathological processes. The cytosolic fraction of bovine brain contains multiple forms of NMT activity whereas bovine spleen contains only a single form. In bovine brain and spleen, the cytosol contained majority of NMT activity. In contrast, rabbit colon and rat liver NMT activity was predominantly particulate. Regional differences in NMT activity have been observed in both rabbit intestine and bovine brain. Results from our laboratory along with the existing knowledge, provide evidence for the existence of tissue specific isozymes of NMT.
    Type of Medium: Electronic Resource
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  • 10
    ISSN: 1573-4919
    Keywords: signal transduction ; calmodulin ; phosphodiesterase ; Ca2+ ; cAMP
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract The bovine heart calmodulin-dependent phosphodiesterase can be phosphorylated by cAMP-dependent protein kinase, resulting in a decrease in the enzyme's affinity for calmodulin. The phosphorylation of calmodulin-dependent phosphodiesterase is blocked by Ca2+ and calmodulin and reversed by the calmodulin-dependent phosphatase. The dephosphorylation is accompanied by an increase in the affinity of the phosphodiesterase for calmodulin. The CaM-dependent phosphodiesterase isozymes of heart and brain are regulated by calmodulin, but the affinity for calmodulin are different. Furthermore, the bovine heart CaM-dependent phosphodiesterase isozyme in stimulated at much lower Ca2+ concentration than the bovine brain isozymes. Results from this study suggest that the activity of this phosphodiesterase is precisely regulated by cross-talk between Ca2+ and cAMP signalling pathways.
    Type of Medium: Electronic Resource
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