Report medicine
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The K103N substitution is a frequently observed HIV-1 RT mutation in patients who do not respond to combinationtherapy. The drugs Efavirenz, MSC194 and PNU142721 belong to the recent generation of NNRTIs characterized by an improved resistance profile to the most common single point mutations within HIV-1 RT, including the K103N mutation. In the present study we present structural observations from Efavirenz in complex with wild-type protein and the K103N mutant and PNU142721 and MSC194 in complex with the K103N mutant.
8p system191 01-06-2013 41 4 Download
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The dinitrogenase component proteins of the conventional Mo nitrogenase (MoFe protein) and of the alternative Fe-only nitrogenase (FeFe protein) were both isolated and purified from Rhodobacter capsulatus, redox-titrated according to the same procedures and subjected to an EPR spectroscopic comparison. In the course of an oxidative titration of the MoFe protein (Rc1Mo) three significant S ¼ 1/2 EPR signals deriving from oxidized states of the P-cluster were detected: (1) a rhombic signal (g ¼ 2.07, 1.96 and 1.
12p system191 01-06-2013 31 4 Download
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DNA of prokaryotes is in a nonequilibrium structural state, characterized as ÔactiveÕ DNA supercoiling. Alterations in this state aect many life processes and a homeostatic control of DNA supercoiling has been suggested [Menzel, R. & Gellert, M. (1983) Cell 34, 105±113]. We here report on a new method for quantifying homeostatic control of the high-energy state of in vivo DNA. The method involves making small perturbation in the expression of topoisomerase I, and measuring the eect on DNA supercoiling of a reporter plasmid and on the expression of DNA gyrase....
8p system191 01-06-2013 35 5 Download
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The two group I introns Nae.L1926 and Nmo.L2563, found at two different sites in nuclear LSU rRNA genes of Naegleria amoebo-flagellates, have been characterized in vitro. Their structural organization is related to that of the mobile Physarum intron Ppo.L1925 (PpLSU3) with ORFs extending the L1-loop of a typical group IC1 ribozyme. Nae.L1926, Nmo.L2563 and Ppo.L1925 RNAs all selfsplice in vitro, generating ligated exons and full-length intron circles as well as internal processed excised intron RNAs....
9p system191 01-06-2013 26 5 Download
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The human b-globin gene locus is the subject of intense study, and over the past two decades a wealth of information has accumulated on how tissue-specific and stage-specific expression of its genes is achieved. The data are extensive and it would be difficult, if not impossible, to formulate a comprehensive model integrating every aspect of what is currently known. In this review, we introduce the fundamental characteristics of globin locus regulation as well as questions on which much of the current research is predicated.
11p system191 01-06-2013 50 4 Download
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The importance of two putative Zn2+-binding (Asp347, Glu429) and two catalytic (Arg431, Lys354) residues in the tomato leucine aminopeptidase (LAP-A) function was tested. The impact of substitutions at these positions, corresponding to the bovine LAP residues Asp255, Glu334, Arg336, and Lys262, was evaluated in His6–LAP-A fusion proteins expressed in Escherichia coli. Sixty-five percent of the mutant His6–LAP-A proteins were unstable or had complete or partial defects in hexamer assembly or stability. The activity of hexameric His6–LAP-As on Xaa-Leu and Leu-Xaa dipeptides was tested.
11p system191 01-06-2013 41 4 Download
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The binding of Thermomyces lanuginosa lipase and its mutants [TLL(S146A), TLL(W89L), TLL(W117F, W221H, W260H)] to the mixed micelles of cis-parinaric acid/ sodium taurodeoxycholate at pH 5.0 led to the quenching of the intrinsic tryptophan fluorescence emission (300–380 nm) and to a simultaneous increase in the cis-parinaric acid fluorescence emission (380–500 nm). These findings were used to characterize the Thermomyces lanuginosa lipase/cisparinaric acid interactions occurring in the presence of sodium taurodeoxycholate....
9p system191 01-06-2013 50 5 Download
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In the course of trying to understand the pathogenesis of leishmaniasis in relation to extracellular matrix (ECM) elements, laminin, a major ECM protein, has been found to bind saturably and with high affinity to a 67-kDa cell surface protein of Leishmania donovani. This interaction involves a single class of binding sites, which are ionic in nature, conformation-dependent and possibly involves sulfhydryls. Binding activity was significantly enhanced by Zn2+, an effect possibly mediated through Cys-rich zinc finger-like sequences on laminin....
8p system191 01-06-2013 43 4 Download
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Dystrobrevin is one of the intracellular components of the transmembrane dystrophin–glycoprotein complex (DGC). The functional role of this complex in normal and pathological situations has not yet been clearly established. Dystrobrevin disappears from the muscle membrane in Duchenne muscular dystrophy (DMD), which results from dystrophin mutations, as well as in limb girdle muscular dystrophies (LGMD), which results from mutations affecting other members of the DGC complex.
6p system191 01-06-2013 36 5 Download
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Ferritin from the spleen of the Antarctic teleost Trematomus bernacchii is composed of a single subunit that contains both the ferroxidase center residues, typical of mammalian H chains, and the carboxylate residues forming the micelle nucleation site, typical of mammalian L chains. Comparison of the amino-acid sequence with those available from lower vertebrates indicates that T. bernacchii ferritin can be classified as an M-type homopolymer. Interestingly, the T. bernacchii ferritin chain shows 85.7% identity with a coldinducible ferritin chain of the rainbow trout Salmo gairdneri....
7p system191 01-06-2013 32 4 Download
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Shikimate kinase was chosen as a convenient representative example of the subclass of a/b proteins with which to examine the mechanism of protein folding. In this paper we report on the refolding of the enzyme after denaturation in urea. As shown by the changes in secondary and tertiary structure monitored by far UV circular dichroism (CD) and fluorescence, respectively, the enzyme was fully unfolded in 4 M urea. From an analysis of the unfolding curve in terms of the two-state model, the stability of the folded state could be estimated as 17 kJÆmol)1.
9p system191 01-06-2013 48 5 Download
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FTIR spectroscopy has been applied to study the coordination structures of Mg2þ and Ca2þ ions bound in Akazara scallop troponin C (TnC), which contains only a single Ca2þ binding site. The region of the COO – antisymmetric stretch provides information about the coordination modes of COO – groups to the metal ions: bidentate, unidentate, or pseudo-bridging. Two bands were observed at 1584 and 1567 cm21 in the apo state, whereas additional bands were observed at 1543 and 1601 cm21 in the Ca2þ-bound and Mg2þ-bound states, respectively.
7p system191 01-06-2013 41 2 Download
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Mer belongs to the Tyro 3 family of receptor tyrosine kinases (RTKs). Together with Axl and Rse, the three RTKs are believed to play important functional roles in the male gonads because gene knockout male mice lacking all of these receptors are infertile. In the present study, postnatal expression of Axl and Rse in mouse testes decreased during maturation while expression of Mer increased age-dependently during testicular development.
12p system191 01-06-2013 44 2 Download
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Trehalose metabolism is an essential component of the stress response in yeast cells. In this work we show that the products of the principal genes involved in trehalose metabolism in Schizosaccharomyces pombe, tps1+ (coding for trehalose6-P synthase, Tps1p), ntp1+ (encoding neutral trehalase, Ntp1p) and tpp1+ (that codes for trehalose-6-P phosphatase, Tpp1p), interact in vitro with each other and with themselves to form protein complexes. Disruption of the gene tps1+ blocks the activation of the neutral trehalase induced by heat shock but not by osmotic stress.
9p system191 01-06-2013 28 4 Download
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Porcine heart cytoplasmic malate dehydrogenase (s-MDH) is a dimeric protein (2 · 35 kDa). We have studied equilibrium unfolding and refolding of s-MDH using activity assay, fluorescence, far-UV and near-UV circular dichroism (CD) spectroscopy, hydrophobic probe-1-anilino8-napthalene sulfonic acid binding, dynamic light scattering, and chromatographic (HPLC) techniques. The unfolding and refolding transitions are reversible and show the presence of two equilibrium intermediate states.
11p system191 01-06-2013 39 4 Download
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With the aim to distinguish between local and global conformational changes induced by trifluoroethanol in RNase A, spectroscopic and activity measurements in combination with proteolysis by unspecific proteases have been exploited for probing structural transitions of RNase A as a function of trifluoroethanol concentration. At 30% (v/v) trifluoroethanol (pH 8.0; 25 °C), circular dichroism and fluorescence spectroscopy indicate a cooperative collapse of the tertiary structure of RNase A coinciding with the loss of its enzymatic activity....
7p system191 01-06-2013 49 3 Download
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Cannabinoid receptors and their endogenous ligands, the endocannabinoids, have been detected in several blood immune cells, including monocytes/macrophages, basophils and lymphocytes. However, their presence in dendritic cells, which play a key role in the initiation and development of the immune response, has never been investigated.
8p system191 01-06-2013 29 4 Download
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The transcription factor serum response factor (SRF) regulates expression of growth factor-dependent genes and muscle-specific genes in vertebrates. Homologous factors regulate differentiation of some ectodermic tissues in invertebrates. To explore the molecular basis of these different physiological functions, the functionality of human, Drosophila melanogaster and Artemia franciscana SRFs in mammalian cells has been compared in this article. D. melanogaster and, to a lesser extend, A.
9p system191 01-06-2013 34 5 Download
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In this study we describe the isolation of three genes of the CYP11B family of the guinea pig. CYP11B1 codes for the previously described 11b-hydroxylase [Bulow, H.E., Mobius, ¨ ¨ K., Bahr, V. & Bernhardt, R. (1996) Biochem. Biophys. Res. ¨ Commun. 221, 304–312] while CYP11B2 represents the aldosterone synthase gene. As no expression for CYP11B3 was detected this gene might represent a pseudogene.
9p system191 01-06-2013 40 3 Download
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Certain amino acids, like glutamine and leucine, induce an anabolic response in liver. They activate p70 ribosomal protein S6 kinase (p70S6K) and acetyl-CoA carboxylase (ACC) involved in protein and fatty acids synthesis, respectively. In contrast, the AMP-activated protein kinase (AMPK), which senses the energy state of the cell and becomes activated under metabolic stress, inactivates by phosphorylation key enzymes in biosynthetic pathways thereby conserving ATP.
9p system191 01-06-2013 50 5 Download