http://hdl.handle.net/10033/108394 Sun, 19 May 2013 18:04:23 GMT 2013-05-19T18:04:23Z http://hdl.handle.net/10033/276164 Title: Growth Medium-Dependent Glycine Incorporation into the Peptidoglycan of Caulobacter crescentus. Authors: Takacs, Constantin N; Hocking, Jason; Cabeen, Matthew T; Bui, Nhat Khai; Poggio, Sebastian; Vollmer, Waldemar; Jacobs-Wagner, Christine Abstract: The peptidoglycan (PG) is a macromolecular component of the bacterial cell wall that maintains the shape and integrity of the cell. The PG of , unlike that of many other Gram-negative bacteria, has repeatedly been shown to contain significant amounts of glycine. This compositional peculiarity has been deemed an intrinsic characteristic of this species. By performing a comprehensive qualitative and quantitative analysis of the PG by high-performance liquid chromatography (HPLC) and mass spectrometry (MS), we show here that glycine incorporation into the PG depends on the presence of exogenous glycine in the growth medium. High levels of glycine were detected at the fifth position of the peptide side chains of PG isolated from cells grown in the complex laboratory medium PYE or in defined medium (M2G) supplemented with casamino acids or glycine alone. In contrast, glycine incorporation was undetectable when cells were grown in M2G medium lacking glycine. Remarkably, glycine incorporation into peptidoglycan occurred even in the presence of low millimolar to sub-millimolar concentrations of free glycine. High glycine content in the PG had no obvious effects on growth rates, mode of PG incorporation or cell morphology. Hence, the PG is able to retain its physiological functions in cell growth and morphogenesis despite significant alterations in its composition, in what we deem to be unprecedented plasticity. Tue, 01 Jan 2013 00:00:00 GMT http://hdl.handle.net/10033/276164 2013-01-01T00:00:00Z http://hdl.handle.net/10033/270921 Title: Activity-guided screening of bioactive natural compounds implementing a new glucocorticoid-receptor-translocation assay and detection of new anti-inflammatory steroids from bacteria. Authors: Kaufmann, Katrin; Simmons, Luke; Herrmann, Jennifer; Schwär, Gertrud; Luniak, Nora; Müller, Rolf Abstract: Using an in vitro cell-based assay in a flow-design, we have applied activity-guided screening to search for new bioactive compounds isolated from microorganisms. A first assay employs the stable expression of nuclear factor kappa B (NF-κB) while a second assay utilizes the glucocorticoid receptor (GR) coupled to green fluorescent protein. A specialized assay was implemented for both the translocation of NF-κB and to inhibit the translocation of cytokine-mediated NF-κB. In addition, we developed in a wide palette of cell lines used for a highly specialized GR-translocation assay to detect anti-inflammatory effects. This approach demonstrates the straight-forward combination of cell-based assays arranged with an automated fluorescence microscope. This allows for the direct sorting of extracts which are acting in a pharmaceutically interesting way. Initial results using this technique have led to the detection of new anti-inflammatory steroids from bacterial crude extracts. Tue, 01 Jan 2013 00:00:00 GMT http://hdl.handle.net/10033/270921 2013-01-01T00:00:00Z http://hdl.handle.net/10033/266912 Title: The V-ATPase-inhibitor archazolid abrogates tumor metastasis via inhibition of endocytic activation of the Rho-GTPase Rac1. Authors: Wiedmann, Romina M; von Schwarzenberg, Karin; Palamidessi, Andrea; Schreiner, Laura; Kubisch, Rebekka; Liebl, Johanna; Schempp, Christina; Trauner, Dirk; Vereb, Gyorgy; Zahler, Stefan; Wagner, Ernst; Müller, Rolf; Scita, Giorgio; Vollmar, Angelika M Abstract: The abundance of the multimeric vacuolar ATP-dependent proton pump, V-ATPase, on the plasma membrane of tumor cells correlates with the invasiveness of the tumor cell, suggesting the involvement of V-ATPase in tumor metastasis. V-ATPase is hypothesized to create a proton efflux leading to an acidic pericellular microenvironment that promotes the activity of proinvasive proteases. An alternative, not yet explored possibility is that V-ATPase regulates the signaling machinery responsible for tumor cell migration. Here, we show that pharmacologic or genetic reduction of V-ATPase activity significantly reduces migration of invasive tumor cells in vitro. Importantly, the V-ATPase inhibitor archazolid abrogates tumor dissemination in a syngeneic mouse 4T1 breast tumor metastasis model. Pretreatment of cancer cells with archazolid impairs directional motility by preventing spatially restricted, leading edge localization of epidermal growth factor receptor (EGFR) as well as of phosphorylated Akt. Archazolid treatment or silencing of V-ATPase inhibited Rac1 activation, as well as Rac1-dependent dorsal and peripheral ruffles by inhibiting Rab5-mediated endocytotic/exocytotic trafficking of Rac1. The results indicate that archazolid effectively decreases metastatic dissemination of breast tumors by impairing the trafficking and spatially restricted activation of EGFR and Rho-GTPase Rac1, which are pivotal for directed movement of cells. Thus, our data reveals a novel mechanism underlying the role of V-ATPase in tumor dissemination. Thu, 15 Nov 2012 00:00:00 GMT http://hdl.handle.net/10033/266912 2012-11-15T00:00:00Z http://hdl.handle.net/10033/146376 Title: Insights into the complex biosynthesis of the leupyrrins in Sorangium cellulosum So ce690. Authors: Kopp, Maren; Irschik, Herbert; Gemperlein, Katja; Buntin, Kathrin; Meiser, Peter; Weissman, Kira J; Bode, Helge B; Müller, Rolf Abstract: The anti-fungal leupyrrins are secondary metabolites produced by several strains of the myxobacterium Sorangium cellulosum. These intriguing compounds incorporate an atypically substituted γ-butyrolactone ring, as well as pyrrole and oxazolinone functionalities, which are located within an unusual asymmetrical macrodiolide. Previous feeding studies revealed that this novel structure arises from the homologation of four distinct structural units, nonribosomally-derived peptide, polyketide, isoprenoid and a dicarboxylic acid, coupled with modification of the various building blocks. Here we have attempted to reconcile the biosynthetic pathway proposed on the basis of the feeding studies with the underlying enzymatic machinery in the S. cellulosum strain So ce690. Gene products can be assigned to many of the suggested steps, but inspection of the gene set provokes the reconsideration of several key transformations. We support our analysis by the reconstitution in vitro of the biosynthesis of the pyrrole carboxylic starter unit along with gene inactivation. In addition, this study reveals that a significant proportion of the genes for leupyrrin biosynthesis are located outside the core cluster, a 'split' organization which is increasingly characteristic of the myxobacteria. Finally, we report the generation of four novel deshydroxy leupyrrin analogues by genetic engineering of the pathway. Sun, 01 May 2011 00:00:00 GMT http://hdl.handle.net/10033/146376 2011-05-01T00:00:00Z