Andrea Wagner

Bio: Andrea Wagner is an academic researcher from University of Erlangen-Nuremberg. The author has contributed to research in topics: Catabolite repression & CCPA. The author has an hindex of 11, co-authored 12 publications receiving 528 citations.

Identification of a co-repressor binding site in catabolite control protein CcpA

Abstract: The catabolite control protein CcpA is the central regulator of carbon catabolite repression in Bacilli and other Gram-positive bacteria. A comparison of 12 CcpA-like sequences with regulators from the LacI/GalR family defines a CcpA subfamily based on extensive similarities found among CcpAs and not in 32 other members of the family. These amino acids are clustered in three blocks in the CcpA sequence. Their interpretation, assuming a PurR-like fold, reveals that almost all of them are surface exposed and form a continuous patch on the N-terminal subdomain of the protein core extending into the DNA reading head. We introduced nine single amino acid exchanges in the subfamily specific residues of CcpA from Bacillus megaterium. Six mutants, namely CcpA47RS, 79AE, 89YE, 295YR, 299YE and 303RD, are inactive or severely impaired in catabolite repression, underlining their relevance for CcpA function. They are negatively transdominant over wild-type CcpA demonstrating their ability to correctly fold for dimerization. Five of them are unable or impaired in binding HPr-Ser-46-P in vitro, establishing a correlation between catabolite repression efficiency and HPr-Ser-46-P binding. These results support the hypothesis that the conserved region in CcpA is the HPr-Ser-46-P binding site.

Biomimetically- and hydrothermally-grown HAp nanoparticles as reinforcing fillers for dental adhesives.

Abstract: Purpose Differently prepared hydroxyapatite (HAp) nanoparticles were incorporated into the adhesive solution of a commercial adhesive system in order to evaluate the effect on microtensile bond strength to dentin. Materials and methods HAp nanoparticles (20 to 70 nm) were prepared by different processes (biomimetic and hydrothermal) and incorporated into the adhesive of the Adper Scotchbond Multi-Purpose (SBMP) system at various concentrations. Control (unfilled) and experimental groups (filled) were applied onto flat mid-coronal human dentin. Composite crowns were built up and cut into beams with a cross-sectional area of 0.65 ± 0.05 mm2. Specimens were fractured in tension and examined with a scanning electron microscope (SEM) for fractographic analysis. Microtensile bond strength (µTBS) data were analyzed using a two-way ANOVA and modified LSD test at a = 0.05. Analysis of the nanofiller distribution and ultramorphological characterization of the interface was performed by transmission electron microscopy (TEM). Results HAp nanoparticle incorporation into the adhesive of SBMP significantly influenced µTBS to dentin depending on the fillers and the concentration used. A significant increase of the mechanical strength was obtained for the adhesives containing 1% (wt/vol) biomimetic and 5% hydrothermal silanized HAp particles, while the other particle fractions did not influence µTBS significantly. 10% (wt/vol) HAp particles significantly lowered the µTBS irrespective of the particle type used. TEM micrographs revealed nanoparticle dispersion through the adhesive layer but no deposition on or penetration into the hybrid layer. Conclusions HAp nanoparticle incorporation into SBMP increased bond strength to dentin by cohesively reinforcing the interface adhesive layer. At a concentration of 10% (wt/vol), nanofiller incorporation had a negative effect on bond strength.

How Phosphotransferase System-Related Protein Phosphorylation Regulates Carbohydrate Metabolism in Bacteria

Abstract: The phosphoenolpyruvate(PEP):carbohydrate phosphotransferase system (PTS) is found only in bacteria, where it catalyzes the transport and phosphorylation of numerous monosaccharides, disaccharides, amino sugars, polyols, and other sugar derivatives. To carry out its catalytic function in sugar transport and phosphorylation, the PTS uses PEP as an energy source and phosphoryl donor. The phosphoryl group of PEP is usually transferred via four distinct proteins (domains) to the transported sugar bound to the respective membrane component(s) (EIIC and EIID) of the PTS. The organization of the PTS as a four-step phosphoryl transfer system, in which all P derivatives exhibit similar energy (phosphorylation occurs at histidyl or cysteyl residues), is surprising, as a single protein (or domain) coupling energy transfer and sugar phosphorylation would be sufficient for PTS function. A possible explanation for the complexity of the PTS was provided by the discovery that the PTS also carries out numerous regulatory functions. Depending on their phosphorylation state, the four proteins (domains) forming the PTS phosphorylation cascade (EI, HPr, EIIA, and EIIB) can phosphorylate or interact with numerous non-PTS proteins and thereby regulate their activity. In addition, in certain bacteria, one of the PTS components (HPr) is phosphorylated by ATP at a seryl residue, which increases the complexity of PTS-mediated regulation. In this review, we try to summarize the known protein phosphorylation-related regulatory functions of the PTS. As we shall see, the PTS regulation network not only controls carbohydrate uptake and metabolism but also interferes with the utilization of nitrogen and phosphorus and the virulence of certain pathogens.

NO-independent stimulators and activators of soluble guanylate cyclase: discovery and therapeutic potential

Abstract: Soluble guanylate cyclase (sGC) is a key signal-transduction enzyme activated by nitric oxide (NO). Impaired bioavailability and/or responsiveness to endogenous NO has been implicated in the pathogenesis of cardiovascular and other diseases. Current therapies that involve the use of organic nitrates and other NO donors have limitations, including non-specific interactions of NO with various biomolecules, lack of response and the development of tolerance following prolonged administration. Compounds that activate sGC in an NO-independent manner might therefore provide considerable therapeutic advantages. Here we review the discovery, biochemistry, pharmacology and clinical potential of haem-dependent sGC stimulators (including YC-1, BAY 41-2272, BAY 41-8543, CFM-1571 and A-350619) and haem-independent sGC activators (including BAY 58-2667 and HMR-1766).

Survey of the year 2003 commercial optical biosensor literature

Abstract: In the year 2003 there was a 17% increase in the number of publications citing work performed using optical biosensor technology compared with the previous year. We collated the 962 total papers for 2003, identified the geographical regions where the work was performed, highlighted the instrument types on which it was carried out, and segregated the papers by biological system. In this overview, we spotlight 13 papers that should be on everyone's 'must read' list for 2003 and provide examples of how to identify and interpret high-quality biosensor data. Although we still find that the literature is replete with poorly performed experiments, over-interpreted results and a general lack of understanding of data analysis, we are optimistic that these shortcomings will be addressed as biosensor technology continues to mature.

Carbon catabolite repression in bacteria : choice of the carbon source and autoregulatory limitation of sugar utilization

Abstract: Carbon catabolite repression (CCR) in bacteria is generally regarded as a regulatory mechanism to ensure sequential utilization of carbohydrates. Selection of the carbon sources is mainly made at the level of carbohydrate-specific induction. Since virtually all carbohydrate catabolic genes or operons are regulated by specific control proteins and require inducers for high level expression, direct control of the activity of regulators or control of inducer formation is an efficient measure to keep them silent. By these mechanisms, bacteria are able to establish a hierarchy of sugar utilization. In addition to the control of induction processes by CCR, bacteria have developed global transcriptional regulation circuits, in which pleiotropic regulators are activated. These global control proteins, the catabolite gene activator protein (CAP), also known as cAMP receptor protein, in Escherichia coli or the catabolite control protein (CcpA) in Gram-positive bacteria with low GC content, act upon a large number of catabolic genes/operons. Since practically any carbon source is able to trigger global transcriptional control, expression of sugar utilization genes is restricted even in the sole presence of their cognate substrates. Consequently, CAP- or CcpA-dependent catabolite repression serves as an autoregulatory device to keep sugar utilization at a certain level rather than to establish preferential utilization of certain carbon sources. Together with other autoregulatory mechanisms that are not acting at the gene expression level, CCR helps bacteria to adjust sugar utilization to their metabolic capacities. Therefore, catabolic/metabolic balance would perhaps better describe the physiological role of this regulatory network than the term catabolite repression.