Lactacystin is a microbial metabolite isolated from Streptomyces that is now widely used as a selective inhibitor of the 20S proteasome.{10086,2351,10073} Clasto-lactacystin β-lactone was later identified as the active metabolite of lactacystin, resulting from the elimination of cysteine and the formation of a reactive β-lactone. Both lactacystin and its β-lactone metabolite induce differentiation and inhibit cell cycle progression in several tumor cell lines.{1659} Clasto-lactacystin β-lactone irreversibly alkylates subunit X of the 20S proteasome.{10073} It is at least 10 times more active than the parent compound; this increased activity may be a function of increased cell permeability. Inhibition of proteasome peptidase activity results in the accumulation of a variety of ubiquitinated proteins which would normally undergo rapid degradation. Thus, the effects of clasto-lactacystin β-lactone are pleiotropic and depend substantially on the expression pattern of signaling proteins within the treated cell.
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Active metabolite of lactacystin, a widely used selective inhibitor of the 20S proteasome, with at least 10 times better activity; irreversibly alkylates subunit X of the 20S proteasome
Formal name: 1R-[1S-1hydroxy-2-methylpropyl]-4R-methyl-6-oxa-2-azabicyclo[3.2.0]heptane-3,7-dione
Synonyms: Omuralide|β-Clastolactacystin
Molecular weight: 213.2
CAS: 154226-60-5
Purity: ≥95%
Formulation: A solution in methyl acetate
The tetracycline repressor (TetR) is a transcriptional regulator which normally binds tightly to its palindromic tetO operator DNA, blocking gene expression.{17508} Tet causes the repressor to dissociate from the DNA, allowing transcription to occur. A novel reverse TetR (revTetR) requires tetracycline as a co-repressor to bind tetO and block transcription.{17509,17510} Anhydrotetracycline (hydrochloride) is a powerful effector in both the tetracycline repressor (TetR) and reverse TetR (revTetR) systems, binding the Tet repressor 35-fold more strongly than Tet.{17508,17511} Moreover, anhydrotetracycline poorly binds the 30S ribosomal subunit, compared to Tet,{17512} so it does not act as a general inhibitor of translation and is a poor antibiotic. Perhaps related to this, the concentration of anhydrotetracycline that inhibits eukaryotic cell growth is more than a 1,000-fold above the dose that alters transcription through TetR.{17508}
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1,2-Dipalmitoyl-sn-glycero-3-PC (DPPC) is a zwitterionic glycerophospholipid commonly used in the formation of lipid monolayers, bilayers, and liposomes for use in a variety of applications.{14480,24261,14478,14479} It has been used in the formation of proteoliposomes for implantation of γ-glutamyl transpeptidase into human erythrocyte membranes.{14478} Incorporation of glycosphingolipid antigens into DPPC-containing liposomes increases the immunogenicity of the antigens in mice.{14479}
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The PtdIn phosphates play an important role in the generation and transduction of intracellular signals.{8344,4096,14518} PtdIns-(3,4,5)-P3-biotin is an affinity probe which allows the PIP3 to be detected through an interaction with the biotin ligand. This design allows PtdIns-(3,4,5)-P3-biotin to serve as a general probe for any protein with a high affinity binding interaction with inositol-(3,4,5)-triphosphate phospholipids, such as phosphatidylinositol 3-kinase, PTEN, or PH-domain-containing proteins.
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Cyclin-dependent kinases (CDKs) are key regulators of cell cycle progression and are therefore promising targets for cancer therapy. (R)-Roscovitine is a potent inhibitor of Cdk2/cyclin E with an IC50 value of 0.1 µM.{14988} It also inhibits Cdk7/cyclin H, Cdk5/p35, and cell division cycle (cdc)/cyclin B with IC50 values of 0.49, 0.16, and 0.65 µM, respectively.{14987,14988,14991} (R)-Roscovitine inhibits the growth of rapidly proliferating cells with an average IC50 value of 15.2 µM against a panel of 19 human tumor cell lines.{14988} In murine models of polycystic kidney disease, (R)-roscovitine effectively inhibited disease progression at doses of 50-100 mg/kg.{14564}
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