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1.
Cell division in cell suspension cultures can be completely blocked by the growth retardant tetcyclacis at a concentration of 10-4 mol l-1. In rice cells it has been demonstrated that the growth inhibition can be completely overcome by application of cholesterol independent of the duration of pretreatment with tetcyclacis. In suspension cultures of maize and soybean, too, the effect of tetcyclacis on cell division was neutralized by adding cholesterol. Other plant sterols, stigmasterol, campesterol and sitosterol were active in a decreasing order. Modifications in the cholesterol perhydro-cyclopentanophenanthrene-ring system indicate that the hydroxyl group at C-3 and the double bond between C-5 and C-6 in ring B are required for the activity. In contrast, gibberellic acid as well as ent-kaurenoic acid could not compensate retardant effects. Likewise, tetcyclasis did not change the level of gibberellins in rice cells as shown by radioimmunoassay. Thus, it is concluded that in cell suspension cultures sterols play a more important role in cell division than gibberellins.Abbreviation GAx
gibberelin Ax 相似文献
2.
J. G. M. van Nistelrooy J. M. van den Brink J. A. L. van Kan R. F. M. van Gorcom M. A. de Waard 《Molecular & general genetics : MGG》1996,250(6):725-733
TheCYP51 gene encoding eburicol 14-demethylase (P45014DM) was cloned from a genomic library of the filamentous fungal plant pathogenPenicillium italicum, by heterologous hybridisation with the corresponding gene encoding lanosterol 14-demethylase from the yeastCandida tropicalis. The nucleotide sequence of a 1739-bp genomic fragment and the corresponding cDNA clone comprises an open reading frame (ORF) of 1545 bp, encoding a protein of 515 amino acids with a predicted molecular mass of 57.3 kDa. The ORF is interrupted by three introns of 60, 72 and 62 bp. The C-terminal part of the protein includes a characteristic haem-binding domain, HR2, common to all P450 genes. The deducedP. italicum P45014DM protein and the P45014DM proteins fromCandida albicans, C. tropicalis andSaccharomyces cerevisiae share 47.2, 47.0 and 45.8% amino acid sequence identity. Therefore, the cloned gene is classified as a member of theCYP51 family. Multiple copies of a genomic DNA fragment ofP. italicum containing the cloned P450 gene were introduced intoAspergillus niger by transformation. Transformants were significantly less sensitive to fungicides which inhibit P45014DM activity, indicating that the cloned gene encodes a functional eburicol 14-demethylase. 相似文献
3.
Theerg3 gene ofNeurospora crassa was sequenced (EMBL accession no. X77955) and found to encode a protein of 490 amino acid residues with significant homology
to the yeast sterol biosynthetic enzyme C-14 reductase (39% identity) and also to the C-tenninal region in the sequence reported
for the chicken lamin B receptor (41% identity). The possibility that a single protein may possess both lamin B receptor and
sterol C-14 reductase functions might account for non-sterol-biosynthetic effects of mutations in sterol biosynthesis genes
and of inhibitors of sterol biosynthetic enzymes. 相似文献
4.
Saccharomyces cerevisiae, grown aerobically or anaerobically under conditions which induce a requirement for a sterol and an unsaturated fatty acid, synthesized approximately the same amounts of neutral lipid and intracellular low-density vesicles, although the neutral lipids in aerobically-grown cells contained more esterified sterol and less triacylglycerol than those in anaerobically-grown cells. Kluyveromyces fragilis synthesized much less neutral lipid and a smaller quantity of low-density vesicles than S. cerevisiae whether grown at 30°C (generation time 1.1 h) or 20°C (generation time 2.1 h). Both yeasts synthesized highly saturated triacylglycerols, relatively unsaturated phospholipids, and esterified sterols with an intermediate degree of unsaturation irrespective of the conditions under which they were grown. Free sterols in the yeasts were rich in ergosterol and 22(24)-dehydroergosterol, while the esterified sterol fractions were richer in zymosterol. 相似文献
5.
The chemical composition of two plasma membrane fractions from epimastigote forms of Trypanosoma cruzi is reported. Fraction M, a preparation obtained by conventional methods of cell fractionation is composed of 31% proteins, 34% lipids, 16% carbohydrates and 3% of the lipopeptidophosphoglycan. Phospholipids and sterols account for 7.5 and 9%, respectively, of the total mass. Phosphatidylethanolamine is the major phospholipid in fraction M, representing 45% of the total membrane phospholipids. The other fraction, fraction V (vesicles), was obtained by treatment of the cell with a vesiculating agent. This fraction contains 42% lipids, 20% carbohydrates, 13% proteins and 21% of the lipopeptidophosphoglycan. Phospholipids and sterols make up 17 and 8%, respectively, of the total mass of this fraction. Phosphatidylcholine and phosphatidylethanolamine are the main phospholipids found in fraction V. Phosphonolipids and sialic acid have not been detected in either membrane fraction. Sodium dodecyl sulphate polyacrylamide gel electrophoretic analysis show that the glycoproteins ABC and the lipopeptidophosphoglycan are 50- and 10-times more concentrated, respectively, in fractions V and M than in the whole cell homogenate. The high molar sterol/phospholipid ratio found in fraction M suggests that this fraction is less fluid than fraction V, perhaps reflecting a migration of certain membrane components in the presence of the vesiculating agent. Hence, fraction M is, probably, more representative of the epimastigote plasma membrane as a whole than fraction V. 相似文献
6.
In this review, structures of natural products isolated from the soft corals of genus Cladiella and their biological activities are described. 相似文献
7.
Michal Grzmil Brian A. Hemmings 《Biochimica et Biophysica Acta - Proteins and Proteomics》2013,1834(7):1371-1380
Glioblastoma is the most common and aggressive brain tumor type, with a mean patient survival of approximately 1 year. Many previous analyses of the glioma kinome have identified key deregulated pathways that converge and activate mammalian target of rapamycin (mTOR). Following the identification and characterization of mTOR-promoting activity in gliomagenesis, data from preclinical studies suggested the targeting of mTOR by rapamycin or its analogs (rapalogs) as a promising therapeutic approach. However, clinical trials with rapalogs have shown very limited efficacy on glioma due to the development of resistance mechanisms. Analysis of rapalog-insensitive glioma cells has revealed increased activity of growth and survival pathways compensating for mTOR inhibition by rapalogs that are suitable for therapeutic intervention. In addition, recently developed mTOR inhibitors show high anti-glioma activity. In this review, we recapitulate the regulation of mTOR signaling and its involvement in gliomagenesis, discuss mechanisms resulting in resistance to rapalogs, and speculate on strategies to overcome resistance. This article is part of a Special Issue entitled: Inhibitors of Protein Kinases (2012). 相似文献
8.
Sabine Chapuy-Regaud Caroline Subra Mary Requena Philippe de Medina Sawsan Amara Isabelle Delton-Vandenbroucke Bruno Payre Michelle Cazabat Frédéric Carriere Jacques Izopet Marc Poirot Michel Record 《Biochimie》2013
Progesterone, the cationic amphiphile U18666A and a phospholipase inhibitor (Methyl Arachidonyl Fluoro Phosphonate, MAFP) inhibited by 70%–90% HIV production in viral reservoir cells, i.e. human THP-1 monocytes and monocyte-derived macrophages (MDM). These compounds triggered an inhibition of fluid phase endocytosis (macropinocytosis) and modified cellular lipid homeostasis since endosomes accumulated filipin-stained sterols and Bis(Monoacylglycero)Phosphate (BMP). BMP was quantified using a new cytometry procedure and was increased by 1.25 times with MAFP, 1.7 times with U18666A and 2.5 times with progesterone. MAFP but not progesterone or U18666A inhibited the hydrolysis of BMP by the Pancreatic Lipase Related Protein 2 (PLRP2) as shown by in-vitro experiments. The possible role of sterol transporters in steroid-mediated BMP increase is discussed. 相似文献
9.
3-Hydroxy-3-methylglutaryl-CoA reductase (HMGCR) is the target of the statins, important drugs that lower blood cholesterol levels and treat cardiovascular disease. Consequently, the regulation of HMGCR has been investigated in detail. However, this enzyme acts very early in the cholesterol synthesis pathway, with ∼20 subsequent enzymes needed to produce cholesterol. How they are regulated is largely unexplored territory, but there is growing evidence that enzymes beyond HMGCR serve as flux-controlling points. Here, we introduce some of the known regulatory mechanisms affecting enzymes beyond HMGCR and highlight the need to further investigate their control. 相似文献
10.
Sterols play a significant role in many physiological processes affecting membrane organization, transport, permeability, and signal transduction. The development of fluorescent sterol analogs that have immediate functional relevance to the natural biomolecules is one approach to understanding the sterol-driven physiological processes. Visualizing cellular compartments with tailor-made fluorescent molecules through specific labeling methods enables organelle targeting and reveals dynamic information. In this review, we focus on the recent literature published between 2020 and 2022, with particular emphasis on extrinsic fluorophores and their investigations of sterol-driven biological processes involving sterol transport, biomolecular interactions, and biological imaging. 相似文献