a-toolkit-to-enable-hydrocarbon-conversion-in-aqueous-environments

A Toolkit to Enable Hydrocarbon Conversion in Aqueous Environments

This work puts forward a toolkit that enables the conversion of alkanes by Escherichia coli and presents a proof of principle of its applicability. The ...

transient-gene-expression-tobacco-using-gibson-assembly-gene

Transient Gene Expression in Tobacco using Gibson Assembly and the Gene Gun

In order to target a single protein to multiple subcellular organelles, plants typically duplicate the relevant genes, and express each gene separately ...

Delft University of Technology

Harvard University

Harvard Medical School

Proteasomes degrade most proteins in mammalian cells and are established targets of anti-cancer drugs. The majority of proteasome inhibitors are composed of short peptides with an electrophilic functionality (pharmacophore) at the C terminus. All eukaryotic proteasomes have three types of active sites as follows: chymotrypsin-like, trypsin-like, and caspase-like. It is widely believed that active site specificity of inhibitors is determined primarily by the peptide sequence and not the pharmacophore. Here, we report that active site specificity of inhibitors can also be tuned by the chemical nature of the pharmacophore. Specifically, replacement of the epoxyketone by vinyl sulfone moieties further improves the selectivity of β5-specific inhibitors NC-005, YU-101, and PR-171 (carfilzomib). This increase in specificity is likely the basis of the decreased cytotoxicity of vinyl sulfone-based inhibitors to HeLa cells as compared with that of epoxyketone-based inhibitors.

Nature of pharmacophore influences active site specificity of proteasome inhibitors.

Proteasomes degrade the majority of proteins in mammalian cells by a concerted action of three distinct pairs of active sites. The chymotrypsin-like sites are targets of antimyeloma agents bortezomib and carfilzomib. Inhibitors of the trypsin-like site sensitize multiple myeloma cells to these agents. Here we describe systematic effort to develop inhibitors with improved potency and cell permeability, yielding azido-Phe-Leu-Leu-4-aminomethyl-Phe-methyl vinyl sulfone (4a, LU-102), and a fluorescent activity-based probe for this site. X-ray structures of 4a and related inhibitors complexed with yeast proteasomes revealed the structural basis for specificity. Nontoxic to myeloma cells when used as a single agent, 4a sensitized them to bortezomib and carfilzomib. This sensitizing effect was much stronger than the synergistic effects of histone acetylase inhibitors or additive effects of doxorubicin and dexamethasone, raising the possibility that combinations of inhibitors of the trypsin-like site with bortezomib or carfilzomib would have stronger antineoplastic activity than combinations currently used clinically.

Incorporation of non-natural amino acids improves cell permeability and potency of specific inhibitors of proteasome trypsin-like sites.

The 3-hydroxypropionate (3-HPA) bicycle is unique among CO2-fixing systems in that none of its enzymes appear to be affected by oxygen. Moreover, the bicycle includes a number of enzymes that produce novel intermediates of biotechnological interest, and the CO2-fixing steps in this pathway are relatively rapid. We expressed portions of the 3-HPA bicycle in a heterologous organism, E. coli K12. We subdivided the 3-HPA bicycle into four sub-pathways: (1) synthesis of propionyl-CoA from acetyl-CoA, (2) synthesis of succinate from propionyl-CoA, (3) glyoxylate production and regeneration of acetyl-CoA, and (4) assimilation of glyoxylate and propionyl-CoA to form pyruvate and regenerate acetyl-CoA. We expressed the novel enzymes of the 3-HPA bicycle in operon form and used phenotypic tests for activity. Sub-pathway 1 activated a propionate-specific biosensor. Sub-pathway 2, found in non-CO2-fixing bacteria, was reassembled in E. coli using genes from diverse sources. Sub-pathway 3, operating in reverse, generated succinyl-CoA sufficient to rescue a sucAD(-) double mutant of its diaminopimelic acid (DAP) auxotrophy. Sub-pathway 4 was able to reduce the toxicity of propionate and allow propionate to contribute to cell biomass in a prpC(-)(2 methylcitrate synthase) mutant strain. These results indicate that all of the sub-pathways of the 3-HPA bicycle can function to some extent in vivo in a heterologous organism, as indicated by growth tests. Overexpression of certain enzymes was deleterious to cell growth, and, in particular, expression of MMC-CoA lyase caused a mucoid phenotype. These results have implications for metabolic engineering and for bacterial evolution through horizontal gene transfer.

Expression of the sub-pathways of the Chloroflexus aurantiacus 3-hydroxypropionate carbon fixation bicycle in E. coli: Toward horizontal transfer of autotrophic growth.

Plant bioengineers require simple genetic devices for predictable localization of heterologous proteins to multiple subcellular compartments.

Mathias J. Voges

Department of Biotechnology

Delft University of Technology

A Toolkit to Enable Hydrocarbon Conversion in Aqueous Environments

Transient Gene Expression in Tobacco using Gibson Assembly and the Gene Gun

Mathias J. Voges

.css-o250i3{font-size:18px;font-family:Open Sans,sans-serif;line-height:21.6px;}Department of Biotechnology

Delft University of Technology

A Toolkit to Enable Hydrocarbon Conversion in Aqueous Environments

Transient Gene Expression in Tobacco using Gibson Assembly and the Gene Gun

Department of Biotechnology