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Query: UNIPROT:P06889 (Mol)
 630,302 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The temperature dependence of the UV- and CD-spectra of the oligonucleotides 3'-d(A)10-L-(T)10-5' [anti(AT)], 3'-d(A)10-L-d(T)10-3' [par(AT)] and 3'-d(A)10-L-(dT)10-L-(dT)10-5' [tripl(ATT)] (L = -PO(CH2CH2O) 3p-) in the phosphate buffer at pH 7 under different concentrations of NaCL and in the presence or absence of 0.01 M MgCl2 was studied. All registered structural changes are the result of intramolecular processes if the concentrations of the oligonucleotides is low (about 2.2.10(-5) M). Par(AT) and anti(AT) exist in the only two forms, transforming into each other: under low temperatures they exist as hairpins with the parallel or antiparallel orientation of chains accordingly which transform into unfolded chains when the temperature increased. In contrast trip(ATT) exists in the three different forms depending on the temperature and ion conditions. They are: the three- stranded clip, the two-stranded hairpin with a single stranded "tail" and completely unfolded chain. For the first time this work presents thermodynamic parameters of the triplex formation from deoxyoligonucleotides depending on NaCl concentration. We have registered the CD spectra to one-, two-, and three-stranded forms. Ethidium bromide binding to three-stranded "clip" was investigated, and it was established that molecules of the dye may intercalate into the "clip" with formation of stable complexes (the constant of association 10(6) M-1). It is maximum three molecules of ethidium bromid which may bound to one molecule of the three-stranded clip. It has been shown that the suggested synthetic model (three oligonucleotide blocks combined by hydroxyalkyl chains) is the most convenient for physico-chemical investigations of triplexes today.
Mol Biol (Mosk)
PMID:[A triple-stranded "clip" from the oligonucleotide 3'-(dA)10-pO(Ch2Ch2O)3p-(dT)10-pO(CH2CH2O)3-p-(dT)10(-5)]. 149 74

In the pairing reaction between circular gapped and fully duplex DNA, RecA protein first polymerizes on the gapped DNA to form a nucleoprotein filament. Conditions that removed the formation of secondary structure in the gapped DNA, such as addition of Escherichia coli single-stranded DNA binding protein or preincubation in 1 mM-MgCl2, optimized the binding of RecA protein and increased the formation of joint molecules. The gapped duplex formed stable joints with fully duplex DNA that had a 5' or 3' terminus complementary to the single-stranded region of the gapped molecule. However, the joints formed had distinct properties and structures depending on whether the complementary terminus was at the 5' or 3' end. Pairing between gapped DNA and fully duplex linear DNA with a 3' complementary terminus resulted in strand displacement, symmetric strand exchange and formation of complete strand exchange products. By contrast, pairing between gapped and fully duplex DNA with a 5' complementary terminus produced a joint that was restricted to the gapped region; there was no strand displacement or symmetric strand exchange. The joint formed in the latter reaction was likely a three-stranded intermediate rather than a heteroduplex with the classical Watson-Crick structure. We conclude that, as in the three-strand reaction, the process of strand exchange in the four-strand reaction is polar and progresses in a 5' to 3' direction with respect to the initiating strand. The present study provides further evidence that in both three-strand and four-strand systems the pairing and strand exchange reactions share a common mechanism.
J Mol Biol 1992 Jan 05
PMID:RecA protein-promoted homologous pairing and strand exchange between intact and partially single-stranded duplex DNA. 153 Sep 79

The mouse Wnt-1 gene, a target for insertional activation in mouse mammary tumor virus-induced mammary tumors, encodes poorly secreted, cysteine-rich glycoproteins required for proper central nervous system development. We have been analyzing the biosynthesis of Wnt-1 proteins in several cell lines that express Wnt-1 cDNA from heterologous promoters. A protein of 78 kDa was found to be associated with the intracellular forms of Wnt-1 proteins in mammalian and avian cells by using multiple antisera against Wnt-1 proteins. We have identified p78 as the binding protein BiP with anti-BiP antisera and by its release from Wnt-1 immunoprecipitates upon incubation with MgCl2 and ATP. Experiments with a Wnt-1 mutant that lacks the sequence encoding the signal peptide indicates that Wnt-1 proteins must enter the secretory pathway in order to interact with BiP. We demonstrate that Wnt-1 proteins are associated with BiP in cells in which active Wnt-1 proteins are produced, such as a cultured mammary epithelial cell line and Wnt-1 transgenic mouse mammary tumor cells. The association of Wnt-1 proteins with BiP may be a factor in determining the efficiency of secretion of Wnt-1 gene products.
Mol Cell Biol 1992 Feb
PMID:Interaction of Wnt-1 proteins with the binding protein BiP. 153 Oct 88

When isolated from chick oviduct cytosol by antibody adsorption, the inactive progesterone receptor is associated with the two heat shock proteins, hsp90 and hsp70, plus three additional proteins termed p54, p50, and p23 according to their molecular weights. While their functions remain unknown, all of these receptor associated proteins are dissociated upon receptor activation in intact cells. To better understand the assembly and activation mechanisms of progesterone receptor complexes, we have developed a cell-free system for studying receptor interactions with hsp90 and hsp70 and have used this system to examine requirements for hsp90 binding to the receptor. Purified receptor, free of hsp90 and immobilized on an antibody affinity resin, will rebind hsp90 in rabbit reticulocyte lysate when several conditions are met. These include: (1) absence of progesterone, (2) elevated temperature (30 degrees C), (3) presence of ATP, and (4) presence of Mg2+. We have obtained maximal hsp90 binding to receptor when lysate is supplemented with 3 mM MgCl2 and an ATP regenerating system. ATP depletion of lysate by dialysis or ATPase addition blocks hsp90 binding to the receptor. When progesterone is added to pre-formed receptor complexes in reticulocyte lysate it promotes activation and the dissociation of hsp90. This process is also dependent upon ATP. Thus, both the assembly, and activation of the progesterone receptor can be accomplished in the reticulocyte lysate system.
J Steroid Biochem Mol Biol 1992 Mar
PMID:Composition, assembly and activation of the avian progesterone receptor. 156 3

The purine repressor is a putative helix-turn-helix DNA-binding protein that regulates several genetic loci important in purine and pyrimidine metabolism in Escherichia coli. The protein is composed of two domains, an N-terminal DNA-binding domain and a C-terminal core that binds the purine co-repressors, guanine and hypoxanthine. The co-repressor binding domain (residues 53 to 341) has been crystallized from polyethylene glycol 600-MgCl2 solutions. They are of the monoclinic form, space group P2(1), with a = 38.2 A, b = 125.7 A, c = 61.8 A and beta = 100.2 degrees. They diffract to a resolution of at least 2.2 A and contain two monomers per asymmetric unit. The importance of the structural determination of this domain is underscored by the high degree of sequence homology displayed within the effector binding sites among a sub-class of helix-turn-helix proteins, of which LacI and GalR are members. The structure of the PurR co-repressor binding domain will provide a high resolution view of one such domain and could serve as a possible model for future effector site structural determinations. Perhaps more important will be this structure's contribution to the further understanding of how protein-DNA interactions are modulated.
J Mol Biol 1992 Jun 20
PMID:Crystallization and preliminary X-ray studies on the co-repressor binding domain of the Escherichia coli purine repressor. 161 95

An enzyme able to cleave dinucleoside triphosphates has been purified 3,750-fold from Saccharomyces cerevisiae. Contrary to the enzymes previously shown to catabolize Ap4A in yeast, this enzyme is a hydrolase rather than a phosphorylase. The dinucleoside triphosphatase molecular ratio estimated by gel filtration is 55,000. Dinucleoside triphosphatase activity is strongly stimulated by the presence of divalent cations. Mn2+ displays the strongest stimulating effect, followed by Mg2+, Co2+, Cd2+, and Ca2+. The Km value for Ap3A is 5.4 microM (50 mM Tris-HCl [pH 7.8], 5 mM MgCl2, and 0.1 mM EDTA; 37 degrees C). Dinucleoside polyphosphates are substrates of this enzyme, provided that they contain more than two phosphates and that at least one of the two bases is a purine (Ap3A, Ap3G, Ap3C, Gp3G, Gp3C, m7Gp3A, m7Gp3G, Ap4A, Ap4G, Ap4C, Ap4U, Gp4G, and Ap5A are substrates; AMP, ADP, ATP, Ap2A, and Cp4U are not). Among the products, a nucleoside monophosphate is always formed. The specificity of cleavage of methylated dinucleoside triphosphates and the molecular weight of dinucleoside triphosphatase indicate that this enzyme is different from the mRNA decapping enzyme previously characterized (A. Stevens, Mol. Cell. Biol. 8:2005-2010, 1988).
 ...
PMID:Isolation and characterization of a dinucleoside triphosphatase from Saccharomyces cerevisiae. 165 9

Specific binding sites for bovine placental lactogen (bPL) and the lactogenic hormone, prolactin, have been detected in endometrial membranes isolated from uteri of mid-pregnant heifers. The specific binding of human growth hormone (hGH) (used to monitor the presence of lactogenic binding sites) and of bPL was increased approximately 4-fold following treatment of the membranes with 4 M MgCl2. Binding was found to be ligand specific, membrane protein concentration-, time- and temperature-dependent and reversible. Scatchard analysis of bPL and hGH competition binding data revealed curvilinear plots with dissociation constants for the high affinity sites of 4.1 x 10(-11) M and 6.4 x 10(-11) M, respectively. The maximum capacity of binding of bPL at the high affinity site was 21 fmol/mg). membrane protein while approximately twice the level of binding was measured for hGH (39 fmol/mg). Both hGH and bGH, but not ovine prolactin, competed with [125I]bPL for binding. The concentrations of hGH and bGH needed to effectively compete were however 100-fold higher than those required for unlabeled bPL. No specific binding of radiolabeled bGH was detected in endometrial tissue suggesting the absence of bGH receptors. Preferential competition of [125I]hGH binding was observed by prolactin and bPL. From these data it may be inferred that hGH binding is indicative of the presence of both lactogenic (prolactin) and bPL binding sites in endometrial tissue. The presence of distinct bPL receptors in the endometrium from mid-pregnant cows suggests a possible role for bPL in the maintenance of pregnancy.
Mol Cell Endocrinol 1991 Jul
PMID:Distinct placental lactogen and prolactin (lactogen) receptors in bovine endometrium. 166 80

Spontaneous S6 phosphatase activities dephosphorylating Ser(P)-235 and Ser(P)-236 of the ribosomal protein S6 were measured and compared in microsomes and cytosol of rat liver. The substrate used, small (40S) ribosomal subunits 32P-labelled in vitro by protein kinase A, contained phosphorylated S6 (mainly in the diphosphorylated form) and some minor phosphorylated species. The microsomal and cytosolic S6 phosphatase activities displayed a number of distinct properties. The microsomal activity, representing ca 20% of the S6 phosphatase activity in the post-mitochondrial supernatant, was mainly due to a type-1 phosphatase and dephosphorylated only S6. The remaining post-mitochondrial S6 phosphatase activity, which was fully recovered in the cytosol, and appeared to result from a combination of type-1 (43%) and type 2 (57%) phosphatases, acted on S6 as well as on the minor phosphorylated species. The microsomal activity was 50% inhibited by MgCl2 (10 mM) and was stimulated at least 4.3 fold by MnCl2 (1 mM), while the cytosolic activity was inhibited only 18% by Mg2+ (10 mM) and was increased 2.2 fold by Mn2+ (1 mM). The microsomal activity was increased 10% (P less than 0.06) by lower doses of insulin (25 U/Kg) and 14% (P less than 0.05) by vanadate, but was not significantly (P greater than 0.10) affected by larger doses of insulin (100 U/kg), hepatectomy or cycloheximide. By comparison the cytosolic S6 phosphatase activity was unresponsive to insulin and vanadate, but was decreased 14% and 17% (P less than 0.05) by hepatectomy and cycloheximide.(ABSTRACT TRUNCATED AT 250 WORDS)
Mol Cell Biochem 1991 Oct 16
PMID:A comparative study of microsomal and cytosolic S6 phosphatase activities in rat liver. 166 99

The formation of pseudouridine (psi) in U5 RNA during ribonucleoprotein (RNP) assembly was investigated by using HeLa cell extracts. In vitro transcribed, unmodified U5 RNA assembled into an RNP particle with the same buoyant density and sedimentation velocity as did U5 small nuclear RNP from extracts. The greatest amount of psi modification was detected when a combination of S100 and nuclear extracts was used for assembly. psi formation was inhibited when ATP and creatine phosphate or MgCl2 were not included in the assembly reaction, paralleling the inhibition of RNP particle formation. A time course of assembly and psi formation showed that psi modification lags behind RNP assembly and that at very early time points, Sm-reactive U5 small nuclear RNPs are not modified. Two of three psi modifications normally found in U5 RNA were present in RNA incubated in the extracts. Mutations in the form of deletions and truncations were made in the U5 sequence, and the effect of these mutations on psi formation was investigated. A mutation in the area of stem-loop I which contains the psi moieties or in the Sm binding sequence affected psi formation.
Mol Cell Biol 1991 Dec
PMID:Pseudouridine modification of U5 RNA in ribonucleoprotein particles assembled in vitro. 171 77

Thromboxane A2 (TXA2) and prostaglandin H2 (PGH2) are potent constrictors of airway smooth muscle and may mediate some of the pulmonary effects of leukotrienes. To date, the TXA2/PGH2 receptor in lung has not been well characterized. In this report, we describe the evaluation of the TXA2/PGH2 receptor in guinea pig lung membranes using the new radiolabeled TXA2 mimetic [1S(1 alpha,2 beta(5Z),3 alpha(1E,3S*),4 alpha)]-7-[3-(3-hydroxy-4-(4'- iodophenoxy)-1-butenyl)-7-oxabicyclo-[2.2.1]heptan-2-yl]-5-h eptenoic acid (IBOP). IBOP elicited a dose-dependent contraction of guinea pig lung parenchymal strips (EC50 = 3.03 +/- 0.97 nM, three experiments), which was blocked by the TXA2/PGH2 antagonists SQ29548 (pKB = 7.44 +/- 0.2, three experiments), BM13505 (pKB = 6.29 +/- 0.26, three experiments), and I-PTA-OH (pKB = 5.82 +/- 0.36, three experiments). In radioligand binding studies, the binding of [125I]IBOP to guinea pig lung membranes prepared from perfused lungs was saturable, displaceable, and dependent upon protein concentration. Binding was optimal at pH 6.5 and was enhanced by the addition of mono- and divalent cations. The standard assay buffer was 25 mM 3-(N-morpholino)propanesulfonic acid, pH 6.5, 100 mM NaCl, 5 mM MgCl2. Binding was inhibited by pretreatment with dithiothreitol, N-ethylmaleimide, or beta-mercaptoethanol. Binding was unaffected by the addition of guanine nucleotide analogs at concentrations up to 300 microM. Analysis of the time course of binding of [125]IBOP at 30 degrees yielded k-1 = 0.0447 min-1, k1 = 2.49 x 10(8) M-1 min-1, and Kd = k-1/k1 = 180 pM. Computer analysis of equilibrium binding studies using nonlinear methods (LUNDON-1) revealed a single class of noninteracting binding sites with a Kd of 86.9 +/- 11.9 pM and a Bmax of 81.8 +/- 7.7 fmol/mg of protein (three experiments). [125I]IBOP binding to guinea pig lung membranes was inhibited by a series of TXA2/PGH2 receptor agonists and antagonists, with a rank order different from that previously determined for washed guinea pig platelets (Spearman's r = 0.686, p greater than 0.05). [125I]IBOP binding to guinea pig lung membranes was also inhibited by the prostanoids prostaglandin D2, prostaglandin E2, prostaglandin F2 alpha, and 9 alpha,11 beta-prostaglandin F2, all of which have been proposed to act at the TXA2/PGH2 receptor in lung.
Mol Pharmacol 1991 Jan
PMID:Characterization of a thromboxane A2/prostaglandin H2 receptor in guinea pig lung membranes using a radioiodinated thromboxane mimetic. 182 91


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