The presence of antiphospholipid antibodies in plasma is a risk factor for thrombo-embolic complications. In vitro, however, the same antibodies can prolong clotting times in coagulation assays, a ...classic marker for a bleeding tendency. For years this contradiction puzzles many scientists.We now know that the term antiphospholipid antibodies comprises a heterogeneous population of antibodies and there is growing evidence that only subpopulations of antiphospholipid antibodies are relevant for the clinical complication. In combination with new information on the complex interaction between antiphospholipid antibodies, the protein beta2-Glycoprotein I, and cellular surfaces have opened new avenues for the understanding of the pathology of this syndrome.
Geometry optimizations for several spin states of the iron(III)-S-methyl- porphyrin complex, the iron (III)-oxo-S-methyl-porphyrin complex and the respective anions were performed in order to examine ...models for intermediates in the oxidative cycle of cytochrome P450. The aim of this study was to obtain insights into the ground states of the intermediates of this catalytic cycle and to use the ab initio calculated geometries and charge distributions to suggest better and more realistic parameters for forcefields which are generally used for modeling P450s. The results indicate that the ground states of both the iron(III)-S-methyl-porphyrin complex and the iron(III)-oxo-S-methyl-porphyrin complex are sextet spin states (high spin). The ground states of the anions of both complexes are probably quintet spin states. The fact that experimentally a shift from low spin to high spin is observed upon binding of the substrate suggests that the ab initio calculations for the iron(III)-S-methyl-porphyrin complex in vacuum give a correct representation of the (hydrophobic) substrate-bound state of the active site of P450. The ab initio geometries of the iron-porphyrin complexes are very similar to the experimentally observed geometries, except for the longer iron-sulfur bond in ab initio calculations, which is probably caused by the omission of polarization functions on the sulfur atom during the geometry optimization. The charge distribution in all ab initio calculated complexes can be described by a series of concentric rings of alternating charge, thus allowing a relatively large positive charge on the iron atom. The commonly used forcefields generally underestimate the charge differences between the iron atom and the different parts of the porphyrin moiety or ignore the charges completely. Although forcefield calculations can reproduce the experimental geometry of iron-porphyrin moieties, extension of the forcefields with charges obtained from ab initio calculations should give a better description of the heme moiety in protein modeling and docking experiments.
Positive regulation of jun/AP-1 by E1A de Groot, R; Foulkes, N; Mulder, M ...
Molecular and Cellular Biology,
01/1991, Volume:
11, Issue:
1
Journal Article
The sex pheromone of
Scrobipalpula absoluta (Meyrick) (Lepidoptera: Gelechiidae) was identified as a 92:8 mixture of (3
E,8
Z,11
Z)-3,8,11-tetradecatrienyl acetate (
1) and (3
E,8
...Z)-3,8-tetradecadienyl acetate (
2) through mass spectrometric investigation of the dimethyl disulphide derivatives of excised sex pheromone glands. It is the first time that this method was used for triple unsaturated straight chain molecules. Compound (
2) was identified as a new pheromone component. A synthetic mixture of the two identified compounds proved to be attractive in wind tunnel experiments.
A new sex pheromone compound (3
E,8
Z)-3,8-tetradecadienyl acetate (
2) for
Scrobipalpula absoluta has been identified. GC-MS analysis of DMDS derivatives of
1 and related compounds has been applied successfully to determine all three double bond positions.
Chloride (Cl-) channels are important in the regulation of salt and water transport in secretory epithelial cells. A disturbed Cl- secretion is the most consistent characteristic in the genetic ...disease cystic fibrosis. An outwardly rectifying Cl- channel (OR) with a conductance of 25-50 pS had been proposed to play a major role in Cl- secretion. Activation by Ca2+ and the protein kinases (PK) A and C (at less than 10 nM Ca2+) as well as inhibition by PKC (at 1 microM Ca2+) has been reported. In the present study, we have identified and characterized the OR in HT29.cl19A human colon carcinoma cells. The OR displayed a conductance of 31 +/- 4 pS (n = 25). Its open probability in 10 nM Ca2+ was voltage-dependent in 50% of the patches, starting from 0.2 at -70 mV to 0.8 at 70 mV. The spontaneous activation in excised inside-out patches at -60 mV was Ca(2+)-dependent and decreased from 29% in 1 mM Ca2+ to 2% in 10 nM Ca2+. Active OR were found in (a) 25% of patches exposed to 10 nM Ca2+, ATP and cAMP only, (b) 42% of the patches exposed to 10 nM Ca2+, ATP and the catalytic subunit of PKA (CAK) and (c) 67% of the patches exposed to 1 mM Ca2+, ATP plus CAK. Inhibition of voltage-activated channels by addition of PKC in 1 microM or 1 mM Ca2+ was not observed. Attempts to activate the OR in cell-attached patches by increasing cAMP levels under different experimental conditions were unsuccessful.
Positive Regulation of jun/AP-1 by E1A de Groot, Rolf; Foulkes, Nicholas; Mulder, Maarten ...
Molecular and cellular biology,
19/1/1/, Volume:
11, Issue:
1
Journal Article
Peer reviewed
Proteins encoded by the adenovirus E1A oncogene are capable of positive and negative transcriptional regulation of both viral and cellular genes. E1A regulatory function is commonly thought to ...involve modifications of specific cellular factors that interact with responsive promoters. In this report we present evidence that E1A induces the activity of the jun/AP-1 transcription factor in three different cell types: P19, JEG-3, and HeLa. AP-1 binds to 12-O-tetradecanoylphorbol-13-acetate (TPA)-responsive elements (TREs); therefore, E1A might modulate a specific signal transduction pathway normally induced by activation of the protein kinase C. Binding of jun/AP-1 to a TRE is induced in all cell types studied when E1A is expressed. We observe that the expression of endogenous c-jun and jun B genes is induced by E1A, which directly transactivates the promoters of c-fos, c-jun, and jun B. Similar inducibility is obtained by treatment with retinoic acid and differentiation of P19 embryonal carcinoma cells. The E1A 13S product transactivates TRE sequences and cooperates with c-jun in the transcriptional stimulation. The 12S E1A product does not activate a TRE sequence, but cotransfection with c-jun circumvents this lack of stimulation. Coexpression of c-fos and E1A 12S, however, blocks the transactivation by c-jun, suggesting an important role for fos in determining the dominance of the 12S or 13S protein.
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