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)

Several proteins in sarcoplasmic reticulum preparations move in a band with a mobility, in sodium dodecyl sulfate-polyacrylamide gels (0.1 M phosphate buffer, pH 7.0), corresponding to a molecular mass of about 55,000 daltons. Only one of these proteins is the high affinity calcium binding protein. An intrinsic glycoprotein is also present in this band, and it is this glycoprotein which is found in vesicles reconstituted after dissolution of sarcoplasmic reticulum in deoxycholate. Both of these proteins are found in rather constant ratios with the ATPase in light, intermediate, and heavy sarcoplasmic reticulum vesicles. Transverse tubular vesicles can be isolated from the heavy sarcoplasmic reticulum vesicles after disruption of the membrane in a French pressure cell (Lau, Y.H., Caswell, A.H., and Brunschwig, J.P. (1977) J. Biol. Chem. 252, 5565-5574). These vesicles are enriched in their content of the high affinity calcium binding and depleted of the intrinsic glycoprotein. Cycloheptaamylose . fluorescamine complex (CFC) labels the intrinsic glycoprotein heavily indicating that it is at least partially exposed on the cytoplasmic surface of sarcoplasmic reticulum membranes. Since the carbohydrate component of the protein must lie in luminal spaces, it is inferred that the intrinsic glycoprotein is a transmembrane protein. The high affinity calcium binding protein is not labeled by CFC indicating that it is not exposed on the cytoplasmic surface of sarcotubular vesicles. The protein is also not affected by proteolytic digestion of sarcoplasmic reticulum vesicles and can be isolated intact from trypsin-digested vesicles. It is not removed from sarcoplasmic-reticulum vesicles by washing with buffers containing Chelex 100 or ethylene glycol bis(beta-aminoethyl ether)N,N,N',N'-tetraacetic acid (EGTA). These data show that the high affinity calcium binding protein is localized in the interior of the sarcotubular system and suggest that it might be common to both sarcoplasmic reticulum and transverse tubular membranes.
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PMID:Localization of the high affinity calcium binding protein and an intrinsic glycoprotein in sarcoplasmic reticulum membranes. 676 47

The biosynthetic machinery in the melanotrope cells of the Xenopus intermediate pituitary is primarily dedicated to the generation of proopiomelanocortin (POMC)-derived, melanophore-stimulating peptides. Transfer of the animal to a black background stimulates the production of these peptides and causes a dramatic increase in POMC mRNA levels. To identify genes involved in the biosynthesis and regulated release of peptide hormones, we differentially screened an intermediate pituitary cDNA library of toads adapted to a black background with cDNA probes derived from intermediate pituitary mRNA of black- and white-adapted animals. Here we report the identification of twelve distinct genes whose expression levels in the melanotropes are regulated in coordination with that of POMC. Four of these genes are novel while the others code for translocon-associated proteins, a lumenal cysteine protease of the endoplasmic reticulum, prohormone-processing enzymes, members of the granin family and a transmembrane protein presumably involved in the assembly and/or specific functioning of vacuolar H(+)-ATPase from secretory granules. Our results indicate that a wide variety of both soluble and membrane-associated components of the secretory pathway is recruited in physiologically activated, peptide hormone-producing cells.
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PMID:Molecular probing of the secretory pathway in peptide hormone-producing cells. 759 90

Ductin is a highly conserved and polytopic transmembrane protein which is the subunit c component of the vacuolar H(+)-ATPase (V-ATPase) and a component of a connexon channel of gap junctions. Previous studies have suggested that ductin in the V-ATPase has the opposite orientation of ductin in a connexon. Using an in vitro translation system coupled to microsomes derived from the endoplasmic reticulum, we show that ductin is co-translationally inserted into the membrane bilayer, suggesting a dependency on the signal recognition particle for synthesis. By attaching a C-terminal polypeptide derived from beta-lactamase and by using cysteine replacement coupled to chemical labelling, we show that ductin is inserted into the microsomal membrane in both orientations in similar proportions. In contrast, squid rhodopsin appears to be inserted in a single orientation. Changing conserved charged residues at the N-terminus of ductin does not affect the ratio of the two orientations. Once in the microsomal membrane, ductin assembles into an oligomeric complex which contains a pore accessible to a water-soluble probe, reminiscent of the ductin complex found in the V-ATPase and a connexon.
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PMID:Membrane insertion and assembly of ductin: a polytopic channel with dual orientations. 764 80

Phospholamban (PLB) is a small, transmembrane protein that resides in the cardiac sarcoplasmic reticulum (SR) and regulates the activity of Ca(2+)-ATPase in response to beta-adrenergic stimulation. We have used the baculovirus expression system in Sf21 cells to express milligram quantities of wild-type PLB. After purification by antibody affinity chromatography, the function of this recombinant PLB was tested by reconstitution with Ca(2+)-ATPase purified from skeletal SR. The results obtained with recombinant PLB were indistinguishable from those obtained with purified, canine cardiac PLB. In particular, PLB reduced the apparent calcium affinity of Ca(2+)-ATPase but had no effect on Vmax. At pCa 6.8, PLB inhibited both calcium uptake and ATPase activity of Ca(2+)-ATPase by 50%. This inhibition was fully reversed by addition of a monoclonal antibody to PLB, which mimics the physiological effects of PLB phosphorylation. Maximal PLB regulatory effects occurred at a molar stoichiometry of approximately 3:1, PLB/Ca(2+)-ATPase. We also investigated peptides corresponding to the two main domains of PLB. The membrane-spanning domain, PLB26-52, appeared to uncouple ATPase hydrolysis from calcium transport, even though the permeability of the reconstituted vesicles was not altered. The cytoplasmic peptide, PLB1-31, had little effect, even at a 300:1 molar excess over Ca(2+)-ATPase.
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PMID:Functional reconstitution of recombinant phospholamban with rabbit skeletal Ca(2+)-ATPase. 772 63

The Ca-ATPase in the cardiac sarcoplasmic reticulum membrane is regulated by an amphipathic transmembrane protein, phospholamban. We have used time-resolved phosphorescence anisotropy to detect the microsecond rotational dynamics, and thereby the self-association, of the Ca-ATPase as a function of phospholamban phosphorylation and physiologically relevant calcium levels. The phosphorylation of phospholamban increases the rotational mobility of the Ca-ATPase in the sarcoplasmic reticulum bilayer, due to a decrease in large-scale protein association, with a [Ca2+] dependence parallel to that of enzyme activation. These results support a model in which phospholamban phosphorylation or calcium free the enzyme from a kinetically unfavorable associated state.
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PMID:The physical mechanism of calcium pump regulation in the heart. 791 99

The oligomeric state of the chicken liver receptor (chicken hepatic lectin), which mediates endocytosis of glycoproteins terminating with N-acetylglucosamine, has been investigated using physical methods as well as chemical cross-linking. Receptor isolated from liver and from transfected rat fibroblasts expressing the full-length polypeptide is a homotrimer immediately following solubilization in non-ionic detergent, but forms the previously observed hexamer during purification. These results are most consistent with the presence of a trimer of receptor polypeptides in liver membranes and in transfected cells. Analysis of truncated receptors reveals that the C-terminal extracellular portion of this type-II transmembrane protein does not form stable oligomers when isolated from the membrane anchor and cytoplasmic tail. The behaviour of chimeric receptors, in which the cytoplasmic tail of the glycoprotein receptor is replaced with the corresponding segments of rat liver asialoglycoprotein receptor or the beta-subunit of Na+,K(+)-ATPase, or with unrelated sequences from globin, indicates that the cytoplasmic tail influences oligomer stability. Replacement of N-terminal portions of the receptor with corresponding segments of influenza virus neuraminidase results in formation of tetramers, suggesting that the membrane anchor and flanking sequences are important determinants of oligomer formation.
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PMID:Determinants of oligomeric structure in the chicken liver glycoprotein receptor. 850 42

We have demonstrated that sodium pentobarbital inhibited the activation of the human red blood cell plasma membrane Ca(2+)-ATPase produced by dimerization of enzyme monomers or by calmodulin binding to enzyme monomers. The effects of the barbiturate were dose-dependent. Both Vmax and Ca2+ affinity were reduced. The Ca(2+)-ATPase activity of the dimeric enzyme was distinctly less sensitive with respect to the effective inhibitory concentrations of pentobarbital and to the rate of onset of inhibition than was the calmodulin-dependent activation of enzyme monomers. Temperature dependence of the inhibition was in agreement with direct, nonpolar interactions of pentobarbital with a water-exposed nonpolar patch on the surface of this transmembrane protein. The barbiturate prevented the increase of intrinsic tryptophan fluorescence associated with substrate Ca2+ binding to the enzyme dimer. On the basis of the barbiturate effects we propose a model for the action of detergent-like compounds on the enzyme. They inhibit Ca(2+)-ATPase activity by binding to a nonpolar patch on the water-exposed dimerization surface of the enzyme monomer, part of which is also the binding site for calmodulin. The model assumes that their binding to the nonpolar patch on the monomer interferes with dimerization and weakens but does not prohibit calmodulin binding, whose activation of the enzyme is then submaximal. The model should be applicable to other proteins as the two activation pathways studied have been demonstrated for various enzymes.
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PMID:Mechanism of inhibition of the plasma membrane Ca(2+)-ATPase by barbiturates. 854 71

We recently identified a 28-kDa protein in the intestinal brush border that resembled tropomyosin in terms of size, homology, and alpha helical content. This protein contained 27 heptad repeats, nearly all of which began with leucine, leading to its name zipper protein. Subsequent analysis, however, indicated that both a 49-kDa and a 28-kDa immunoreactive protein existed in intestinal brush-border extracts. Using 5'-rapid amplification of cDNA ends analysis, we extended the N-terminal sequence of zipper protein to the apparent translation start site. This additional sequence contained a putative transmembrane domain and two potential tryptic cleavage sites C-terminal to the transmembrane domain which would release a 28-kDa cytoplasmic protein if utilized. The additional sequence was highly homologous to members of the B-G protein family, a family with no known function. Immunoelectron microscopy showed that zipper protein was confined to the membrane of the microvillus where it was in close association with brush-border myosin 1 (BBM1). Recombinant zipper protein (28-kDa cytoplasmic portion) blocked the binding of actin to BBM1 and inhibited actin-stimulated BBM1 ATPase activity. In contrast, zipper protein had no effect on endogenous or K/EDTA-stimulated BBM1 ATPase activity. Furthermore, zipper protein displaced tropomyosin from binding to actin, suggesting that these homologous proteins bind to the same sites on the actin molecule. We conclude that zipper protein is a transmembrane protein of the B-G family localized to the intestinal epithelial cell microvillus. The extended cytoplasmic tail either in the intact molecule or after tryptic cleavage may participate in regulating the binding and, thus, activation of BBM1 by actin in a manner similar to tropomyosin.
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PMID:Zipper protein, a B-G protein with the ability to regulate actin/myosin 1 interactions in the intestinal brush border. 862 57

Na,K-ATPase, an essential transporter of mammalian cells, is an oligomeric transmembrane protein composed of two subunits, alpha and beta, of which there are several isoforms. In this study, we demonstrate that the alpha1 and alpha2 isoforms of the Na,K-ATPase alpha subunit are modified by the covalent attachment of ubiquitin polymers in COS-7 cells. We propose that polyubiquitination of the Na,K-ATPase alpha subunit may play a role in regulating its degradation.
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PMID:Ubiquitination of Na,K-ATPase alpha1 and alpha2 subunits. 910 5

The effect of the 24-amino-acid-long peptide, PD(1), on rat cerebral cortical Na+/K+ -exchanging ATPase (EC 3.6.1.37) has been studied. Incubation of the enzyme preparation (25 degrees C for 10-25 min) with the peptide (10(-7) - 10(-4) M) did not appreciably affect the activity of the enzyme, only 5-8% activation being registered. On the other hand, PD(1) completely eliminated the cooperative nature of Na+ -binding to Na+/K+ -exchanging ATPase (n(H) decreased from 1.4 to 0.9) and slightly (1.2-fold) decreased the affinity for Na+. ATP, a substrate of activity for Na+/K+ -exchanging ATPase, blocked the PD(1)-promoted effect on the cooperativity for Na+. Incubation of cerebral cortical membranes with 5 x 10(-4) M PD(1) revealed a shift (from 19.5 degrees C to 21.4 degrees C) of the typical break on the Arrhenius plot (15-37 degrees C). Prolonged incubation of enzyme preparation (25 degrees C for 1-2 h) with PD(1) (4.5 x 10(-4) - 0.7 x 10(-2) M) followed by centrifugation of the mixture at 53,000 g for 90 min, resulted in loss of the activity both in the supernatant and the sediment, while the protein content in the supernatant and the sediment remained unchanged. After a short incubation (25 degrees for 10 min) with PD(1) (1 x 10(-6) M), followed by centrifugation, the full activity of Na+/K+ -exchanging ATPase in the sediment was restored. These data suggest that peptitergent PD(1) does not solubilize the transmembrane protein Na+/K+ -exchanging ATPase, although it abolishes the cooperative effect of Na+.
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PMID:Attempt to solubilize Na+/K+-exchanging ATPase with amphiphilic peptide PD1. 925 30


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