Intermediate cells

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 46 5   Download

Liver metabolism is influenced by hormones and nutrients. Amino acids such as glutamine or leucine induce an anabolic response, which resembles that of insulin in muscle and adipose tissue. In this work, the signalling pathways and the effects of insulin were compared to those of glutamine and leucine in isolated hepatocytes from normal and streptozotocin-diabetic rats.

9p system191 01-06-2013 46 5   Download

Previous data showing an increase of receptor binding activity of [R16]VIP, a vasoactive intestinal peptide (VIP) structural analogue containing arginine at the position 16 of its amino acid sequence, have pointed out the importance of a positive charge at this site. Here, the functional characterization of three VIP polyaminated adducts (VIPDap, VIPSpd, and VIPSpm), obtained by a transglutaminasecatalysed reaction between the VIP Gln16 residue and 1,3-diaminopropane (Dap), spermidine (Spd), or spermine (Spm), is reported. ...

9p system191 01-06-2013 42 4   Download

The Sp family is a family of transcription factors that bind to cis-elements in the promoter regions of various genes. Regulation of transcription by Sp proteins is based on interactions between a GC-rich binding site (GGGCGG) in DNA and C-terminal zinc finger motifs in the proteins. In this study, we characterized the GC-rich promoter of the gene for the DNA methyltransferase (Dnmt1) that is responsible for methylation of cytosine residues in mammals and plays a role in gene silencing.

10p system191 01-06-2013 38 4   Download

At the time of implantation in the maternal uterus, the trophectoderm of the pig blastocyst is the source of a massive secretion of interferon-gamma (IFN-c), together with lesser amounts of IFN-d, a unique species of type I IFN. This trophoblastic IFN-c (TrIFN-c) is an unprecedented example of IFN-c being produced spontaneously by an epithelium. We therefore studied some of its structural and biochemical properties, by comparison with pig IFN-c from other sources, either natural LeIFN-c (from adult leucocytes), or recombinant. ...

10p system191 01-06-2013 50 6   Download

Cys341 of carboxypeptidase Y, which constitutes one side of the solvent-accessible surface of the S1 binding pocket, was replaced with Gly, Ser, Asp, Val, Phe or His by site-directed mutagenesis. Kinetic analysis, using Cbz-dipeptide substrates, revealed that polar amino acids at the 341 position increased Km whereas hydrophobic amino acids in this position tended to decrease Km.

6p system191 01-06-2013 40 4   Download

Selenoprotein P (SeP) is a plasma protein that contains up to 10 selenocysteine residues and accounts for about 50% of total selenium in human plasma. We have previously shown that SeP expression in the human liver cell line HepG2 is inhibited by transforming growth factor (TGF)-b1 on a transcriptional level. Smad proteins are the transcriptional mediators of TGF-b signalling and putative Smad-binding elements (SBE) comprising the core sequence CAGACA are present at two positions in the SeP promoter....

6p system191 01-06-2013 35 4   Download

The octadecaneuropeptide (ODN; QATVGDVNTDRPG LLDLK) and its C-terminal octapeptide (OP; RPGLLDLK), which exert anxiogenic activity, have been previously shown to increase intracellular calcium concentration ([Ca21]i) in cultured rat astrocytes through activation of a metabotropic receptor positively coupled to phospholipase C. It has also been found that the [D -Leu5]OP analog possesses a weak antagonistic activity. The aim of the present study was to synthesize and characterize cyclic analogs of OP and [D -Leu5]OP.

13p system191 01-06-2013 32 4   Download

Calmodulin (CaM) is phosphorylated in vitro and in vivo by multiple protein-serine/threonine and protein-tyrosine kinases. Casein kinase II and myosin light-chain kinase are two of the well established protein-serine/threonine kinases implicated in this process. On the other hand, within the protein-tyrosine kinases involved in the phosphorylation of CaM are receptors with tyrosine kinase activity, such as the insulin receptor and the epidermal growth factor receptor, and nonreceptor protein-tyrosine kinases, such as several members of the Src family kinases, Janus kinase 2, and p38Syk....

13p research12 01-06-2013 45 6   Download

Phenylacetaldehyde reductase (PAR) produced by styreneassimilating Corynebacterium strain ST-10 was used to synthesize chiral alcohols. This enzyme with a broad substrate range reduced various prochiral aromatic ketones and b-ketoesters to yield optically active secondary alcohols with an enantiomeric purity of more than 98% enantiomeric excess (e.e.). The Escherichia coli recombinant cells which expressed the par gene could efficiently produce important pharmaceutical intermediates;

9p research12 01-06-2013 43 6   Download

During the development of multicellular organisms, both transient and stable gene expression patterns have to be established in a precisely orchestrated sequence. Evidence from diverse model organisms indicates that this epigenetic program involves not only transcription factors, but also the local structure, composition, and modification of chromatin, which define and maintain the accessibility and transcriptional competence of the nucleosomal DNA template.

6p research12 01-06-2013 33 4   Download

Conventional and saturation transfer electron paramagnetic resonance spectroscopy (EPR and ST EPR) was used to study the orientation of probe molecules in muscle fibers in different intermediate states of the ATP hydrolysis cycle. A separate procedure was used to obtain ST EPR spectra with precise phase settings even in the case of samples with low spectral intensity. Fibers prepared from rabbit psoas muscle were labeled with isothiocyanate spin labels at the reactive thiol sites of the catalytic domain of myosin....

10p research12 01-06-2013 38 6   Download

Methanol:coenzyme M methyltransferase from methanogenic archaea is a cobalamin-dependent enzyme composed of three different subunits: MtaA, MtaB and MtaC. MtaA is a zinc protein that catalyzes the methylation of coenzyme M (HS-CoM) with methylcob(III)alamin. We report zinc XAFS (X-ray absorption fine structure) results indicating that, in the absence of coenzyme M, zinc is probably coordinated by a single sulfur ligand and three oxygen or nitrogen ligands. In the presence of coenzyme M, one (N/O)-ligand was replaced by sulfur, most likely due to ligation of the thiol group of coenzyme M....

7p research12 01-06-2013 52 5   Download

The naturally synchronous plasmodia of myxomycetes synthesize poly(b-L-malic acid), which carries out cell-specific functions. In Physarum polycephalum, poly(b-L-malate) [the salt form of poly(b-L-malic acid)] is highly concentrated in the nuclei, repressing DNA synthetic activity of DNA polymerases by the formation of reversible complexes. To test whether this inhibitory activity is cell-cycle-dependent, purified DNA polymerase a of P.

6p research12 01-06-2013 62 3   Download

The product of agmatine oxidation catalyzed by Pisum sativum L. copper amine oxidase has been identified by means of one- and two-dimensional 1H-NMR spectroscopy to be N-amidino-2-hydroxypyrrolidine. This compound inhibits competitively rat nitric oxide synthase type I and type II (NOS-I and NOS-II, respectively) and bovine trypsin (trypsin) activity, values of Ki being (1.1 ± 0.1) · 10)5 M (at pH 7.5 and 37.0 °C), (2.1 ± 0.1) · 10)5 M (at pH 7.5 and 37.0 °C), and (8.9 ± 0.4) · 10)5 M (at pH 6.8 and 21.0 °C), respectively. ...

9p research12 01-06-2013 31 2   Download

Sugar conjugation is a major pathway for the inactivation and excretion of both endogenous and exogenous compounds. We report here the molecular cloning and functional characterization of a phenol UDP-glucosyltransferase (UGT) from the silkworm, Bombyx mori, which was named BmUGT1. The complete cDNA clone is 1.6 kb, and the gene is expressed in several tissues of fifth-instar larvae, including fat body, midgut, integument, testis, silk gland and haemocytes. The predicted protein comprises 520 amino acids and has  30% overall amino-acid identity with other members of the UGT family.

7p research12 01-06-2013 39 4   Download

The functional replacement of the primary ubiquinone (QA) in the photosynthetic reaction center (RC) from Rhodo-bacter sphaeroideswith synthetic vitamin K derivatives has provided a powerful tool to investigate the electron transfer mechanism. To investigate the binding mode of these qui-nones to theQAbinding sitewe have determined the binding free energy and charge recombination rate from QA ± to D + (kAD) of 29 different 1,4-naphthoquinone derivatives with systematically altered structures.

13p research12 01-06-2013 51 4   Download

Obesity is a central feature of the metabolic syndrome and is associated with increased risk for insulin resistance and type II diabetes. Here, we investigated the contribution of human apoliprotein E3 and mouse apoli-protein E to the development of diet-induced obesity in response to western-type diet. Our data show that apolipoprotein E contributes to the development of obesity and other related metabolic disorders, and that human apolipoprotein E3 is more potent than mouse apolipoprotein E in promoting obesity in response to western-type diet. ...

14p research12 29-04-2013 45 3   Download

Resonance Raman spectroscopy has been used to observe changes in the iron–ligand stretching frequency in photo-product spectra of the proximal cavitymutant ofmyoglobin H93G. The measurements compare the deoxy ferrous state of the heme iron in H93G(L), where L is an exogenous imidazole ligand bound in the proximal cavity, to the pho-tolyzed intermediate of H93G(L)*CO at 8 ns.

8p research12 29-04-2013 42 4   Download

We are interested in constructing a model for the substrate-bindingsiteof fattyacidelongase-13-ketoacylCoAsynthase (FAE1 KCS),the enzyme responsible forproductionof very long chain fatty acids of plant seed oils.Arabidopsis thaliana andBrassica napusFAE1 KCS enzymes are highly homo-logous but the seed oil content of these plants suggests that their substrate specificities differ with respect to acyl chain length.

10p research12 29-04-2013 26 3   Download