Search results for "binding"
showing 10 items of 3896 documents
Proteolytic Processing ofBacillus thuringiensisCryIIIA Toxin and Specific Binding to Brush-Border Membrane Vesicles ofLeptinotarsa decemlineata(Color…
1996
Abstract The mode of action of Bacillus thuringiensis insecticidal proteins in lepidopteran insects is known to involve five steps: ingestion, solubilization, protease activation, binding to midgut membrane receptors, and disruption of the intestinal membrane. Two of these steps, protease activation and binding to midgut membrane receptors, have been analyzed in the major potato pest, the coleoptera Leptinotarsa decemlineata (Colorado potato beetle). Unlike recently proposed, after treatment of the coleopteran-specific B. thuringiensis toxin CryIIIA with gut content from the Colorado potato beetle, a 42-kDa processing polypeptide has been identified. The study of binding to midgut membrane …
Prohibitin, an essential protein for Colorado potato beetle larval viability, is relevant to Bacillus thuringiensis Cry3Aa toxicity
2013
Bacillus thuringienesis (Bt) Cry toxins constitute the most extensively used environmentally safe biopesticide and their mode of action relies on the interaction of the toxins with membrane proteins in the midgut of susceptible insects that mediate toxicity and insect specificity. Therefore, identification of Bt Cry toxin interacting proteins in the midgut of target insects and understanding their role in toxicity is of great interest to exploit their insecticidal action. Using ligand blot, we demonstrated that Bt Cry3Aa toxin bound to a 30kDa protein in Colorado potato beetle (CPB) larval midgut membrane, identified by sequence homology as prohibitin-1 protein. Prohibitins comprise a highl…
Proline-Based Allosteric Inhibitors of Zika and Dengue Virus NS2B/NS3 Proteases
2019
The NS2B/NS3 serine proteases of the Zika and Dengue flaviviruses are attractive targets for the development of antiviral drugs. We report the synthesis and evaluation of a new, proline-based compound class that displays allosteric inhibition of both proteases. The structural features relevant for protease binding and inhibition were determined to establish them as new lead compounds for flaviviral inhibitors. Based on our structure-activity relationship studies, the molecules were further optimized, leading to inhibitors with submicromolar IC50 values and improved lipophilic ligand efficiency. The allosteric binding site in the proteases was probed using mutagenesis and covalent modificati…
Development of rhodesain inhibitors with a 3-bromoisoxazoline warhead
2013
Novel rhodesain inhibitors were obtained by combining an enantiomerically pure 3-bromoisoxazoline warhead with a specific peptidomimetic recognition moiety. All derivatives behaved as inhibitors of rhodesain, with low micromolar Ki values. Their activity against the enzyme was found to be paralleled by an in vitro antitrypanosomal activity, with IC50 values in the mid-micromolar range. Notably, a preference for parasitic over human proteases, specifically cathepsins B and L, was observed.
Identification of Plakortide E from the Caribbean Sponge Plakortis halichondroides as a Trypanocidal Protease Inhibitor using Bioactivity-Guided Frac…
2014
In this paper, we report new protease inhibitory activity of plakortide E towards cathepsins and cathepsin-like parasitic proteases. We further report on its anti-parasitic activity against Trypanosoma brucei with an IC50 value of 5 mu M and without cytotoxic effects against J774.1 macrophages at 100 mu M concentration. Plakortide E was isolated from the sponge Plakortis halichondroides using enzyme assay-guided fractionation and identified by NMR spectroscopy and mass spectrometry. Furthermore, enzyme kinetic studies confirmed plakortide E as a non-competitive, slowly-binding, reversible inhibitor of rhodesain.
Analysis of the MHC Class I Antigen Presentation Machinery in Human Embryonal Carcinomas: Evidence for Deficiencies in TAP, LMP and MHC Class I Expre…
1998
The expression of the major histocompatibility complex (MHC) class I antigens is suppressed in early post-implantation embryonic cells as well as in embryonal carcinoma (EC) cells, but could be upregulated by treatment with interferon (IFN)-gamma or retinoic acid. In a number of human and murine tumours, defects in the expression of the different components of the MHC class I antigen processing machinery, such as the proteasomal subunits LMP-2 and LMP-7 and the peptide transporters TAP-1 and TAP-2, account for impaired MHC class I surface expression. Here, we analysed the constitutive and IFN-gamma regulated mRNA and protein expression of the LMP, TAP and MHC class I molecules in the human …
Bipartite regulation of different components of the MHC class I antigen-processing machinery during dendritic cell maturation
2001
Dendritic cells (DC) are professional antigen-presenting cells (APC) which proceed from immature to a mature stage during their final differentiation. Immature DC are highly effective in terms of antigen uptake and processing, whereas mature DC become potent immunostimulatory cells. Until now, the expression profiles of the major components of the MHC class I antigen-processing machinery (APM) during DC development have not been well characterized. In this study, the mRNA and protein expression levels of the IFN-gamma inducible proteasome subunits, of the proteasome activators PA28, and of key components required for peptide transport and MHC class I-peptide complex assembly have been evalu…
Functional deficiencies of components of the MHC class I antigen pathway in human tumors of epithelial origin
2000
An association between oncogenic transformation and repression of different components of the MHC class I antigen processing machinery (APM) have been described in murine model systems. In order to discover whether a similar correlation exists, human tumor cell lines of distinct histology with altered ras protein were analyzed for the expression of APM components utilizing RT-PCR and Western blot analyses. A heterogeneous expression pattern of MHC class I antigens, TAP peptide transporter, proteasome subunits, proteasome activator PA28 and the chaperones calnexin, calreticulin as well as tapasin was displayed by these tumor cell lines. Single or combined deficiencies in the expression and/o…
Heat Shock Proteins: Cell Protection through Protein Triage
2010
Heat shock proteins (HSPs) are chaperones that catalyze the proper folding of nascent proteins and the refolding of denatured proteins. The ubiquitin-proteasome system is an error-checking system that directs improperly folded proteins for destruction. A coordinated interaction between the HSPs (renaturation) and the proteasome (degradation) must exist to assure protein quality control mechanisms. Although it still remains unknown how the decision of folding vs. degradation is taken, many pieces of evidence demonstrate that HSPs interact directly or indirectly with the proteasome, assuring quite selectively the proteasomal degradation of certain proteins under stress conditions. In this rev…
Characterizing the N-terminal processing motif of MHC class I ligands.
2008
Abstract Most peptide ligands presented by MHC class I molecules are the product of an intracellular pathway comprising protein breakdown in the cytosol, transport into the endoplasmic reticulum, and successive N-terminal trimming events. The efficiency of each of these processes depends on the amino acid sequence of the presented ligand and its precursors. Thus, relating the amino acid composition N-terminal of presented ligands to the sequence specificity of processes in the pathway gives insight into the usage of ligand precursors in vivo. Examining the amino acid composition upstream the true N terminus of MHC class I ligands, we demonstrate the existence of a distinct N-terminal proces…