Molecular and functional charaterization of the ser/thr kinase PknB and phosphatase Stp of Staphylococcus aureus

Um Änderungen in seiner Umwelt wahrnehmen zu können, benötigt S. aureus unterschiedliche Signaltransduktionssysteme. In dieser Arbeit wurde erstmals die Eukaryoten-ähnliche Serin/Threonin-Proteinkinase (STPK) PknB umfassend charakterisiert. Die posttranslationale Proteinmodifikation mittels Phosphorylierung spielt sowohl in Eukaryoten als auch in Prokaryoten eine wichtige Rolle. Man glaubte lange, dass die Phosphorylierung von Serin-, Threonin- und Tyrosinresten ein nur auf Eukaryoten beschränkter Regulationsmechanismus ist. Dagegen wurde die Phosphorylierung an Histidin- und Aspartatresten durch die Zweikomponenten-Systeme allein den Prokaryoten zugeordnet. Die Genomanalysen der letzten Jahre identifizierten jedoch STPKs und Serin/Threonin-Proteinphosphatasen (STPP) in nahezu allen prokaryotischen Genomen. Auch S. aureus codiert für eine STPK, die eine hohe Homologie zu den beschriebenen STPKs aufweist. In dieser Arbeit wurden mittels Microarray-Analyse einer ΔpknB-Mutante im Stamm 8325 erste Hinweise zur Funktion von PknB als Regulator der Zellwandsynthese sowie zentraler Stoffwechselwege gewonnen. Es wurden mittels Phosphopreoteom-Analysen in vivo-Substrate identifiziert und weiterhin die Kinase biochemisch charakterisiert.S. aureus needs effective signal transduction systems to be able to sense a changing environment. In this work we characterize for the first time the regulatory ser/thr protein kinase PknB. The posttranslational protein modification via phosphorylation plays an important role in eukaryotes as well as in prokaryotes. The phosphorylation of proteins on serine, threonine, and tyrosine residues was originally thought to be a mechanism of signal sensing and translation only restricted to eukaryotes. In contrast, prokaryotes were thought to achieve signal transduction exclusively via the phosphorylation of histidine and aspartate residues by using two-component systems. However, recent bacterial genome sequencing identified STPKs and STPPs in almost all bacterial genomes. S. aureus also encodes a STPK, which shows high similarity to the described STPKs. In this study the putative function of PknB as a regulator of cell wall-synthesis as well as central metabolic pathways was analysed by a competitive microarray approach. Furthermore, a phosphoproteome analysis was used to identify in vivo substrates and a biochemical characterization was performed

Structural Analysis of Staphylococcus aureus Serine/Threonine Kinase PknB

Effective treatment of infections caused by the bacterium Staphylococcus aureus remains a worldwide challenge, in part due to the constant emergence of new strains that are resistant to antibiotics. The serine/threonine kinase PknB is of particular relevance to the life cycle of S. aureus as it is involved in the regulation of purine biosynthesis, autolysis, and other central metabolic processes of the bacterium. We have determined the crystal structure of the kinase domain of PknB in complex with a non-hydrolyzable analog of the substrate ATP at 3.0 Å resolution. Although the purified PknB kinase is active in solution, it crystallized in an inactive, autoinhibited state. Comparison with other bacterial kinases provides insights into the determinants of catalysis, interactions of PknB with ligands, and the pathway of activation

A functional yeast survival screen of tumor-derived cDNA libraries designed to identify anti-apoptotic mammalian oncogenes

Yeast cells can be killed upon expression of pro-apoptotic mammalian proteins. We have established a functional yeast survival screen that was used to isolate novel human anti-apoptotic genes overexpressed in treatment-resistant tumors. The screening of three different cDNA libraries prepared from metastatic melanoma, glioblastomas and leukemic blasts allowed for the identification of many yeast cell death-repressing cDNAs, including 28% of genes that are already known to inhibit apoptosis, 35% of genes upregulated in at least one tumor entity and 16% of genes described as both anti-apoptotic in function and upregulated in tumors. These results confirm the great potential of this screening tool to identify novel anti-apoptotic and tumor-relevant molecules. Three of the isolated candidate genes were further analyzed regarding their anti-apoptotic function in cell culture and their potential as a therapeutic target for molecular therapy. PAICS, an enzyme required for de novo purine biosynthesis, the long non-coding RNA MALAT1 and the MAST2 kinase are overexpressed in certain tumor entities and capable of suppressing apoptosis in human cells. Using a subcutaneous xenograft mouse model, we also demonstrated that glioblastoma tumor growth requires MAST2 expression. An additional advantage of the yeast survival screen is its universal applicability. By using various inducible pro-apoptotic killer proteins and screening the appropriate cDNA library prepared from normal or pathologic tissue of interest, the survival screen can be used to identify apoptosis inhibitors in many different systems

Staphylococcal PknB as the First Prokaryotic Representative of the Proline-Directed Kinases

In eukaryotic cell types, virtually all cellular processes are under control of proline-directed kinases and especially MAP kinases. Serine/threonine kinases in general were originally considered as a eukaryote-specific enzyme family. However, recent studies have revealed that orthologues of eukaryotic serine/threonine kinases exist in bacteria. Moreover, various pathogenic species, such as Yersinia and Mycobacterium, require serine/threonine kinases for successful invasion of human host cells. The substrates targeted by bacterial serine/threonine kinases have remained largely unknown. Here we report that the serine/threonine kinase PknB from the important pathogen Staphylococcus aureus is released into the external milieu, which opens up the possibility that PknB does not only phosphorylate bacterial proteins but also proteins of the human host. To identify possible human targets of purified PknB, we studied in vitro phosphorylation of peptide microarrays and detected 68 possible human targets for phosphorylation. These results show that PknB is a proline-directed kinase with MAP kinase-like enzymatic activity. As the potential cellular targets for PknB are involved in apoptosis, immune responses, transport, and metabolism, PknB secretion may help the bacterium to evade intracellular killing and facilitate its growth. In apparent agreement with this notion, phosphorylation of the host-cell response coordinating transcription factor ATF-2 by PknB was confirmed by mass spectrometry. Taken together, our results identify PknB as the first prokaryotic representative of the proline-directed kinase/MAP kinase family of enzymes

Mobile Air Quality Studies (MAQS) - an international project

Due to an increasing awareness of the potential hazardousness of air pollutants, new laws, rules and guidelines have recently been implemented globally. In this respect, numerous studies have addressed traffic-related exposure to particulate matter using stationary technology so far. By contrast, only few studies used the advanced technology of mobile exposure analysis. The Mobile Air Quality Study (MAQS) addresses the issue of air pollutant exposure by combining advanced high-granularity spatial-temporal analysis with vehicle-mounted, person-mounted and roadside sensors. The MAQS-platform will be used by international collaborators in order 1) to assess air pollutant exposure in relation to road structure, 2) to assess air pollutant exposure in relation to traffic density, 3) to assess air pollutant exposure in relation to weather conditions, 4) to compare exposure within vehicles between front and back seat (children) positions, and 5) to evaluate "traffic zone"- exposure in relation to non-"traffic zone"-exposure. Primarily, the MAQS-platform will focus on particulate matter. With the establishment of advanced mobile analysis tools, it is planed to extend the analysis to other pollutants including including NO2, SO2, nanoparticles, and ozone

Birthweight: EN-BIRTH multi-country validation study.

BACKGROUND: Accurate birthweight is critical to inform clinical care at the individual level and tracking progress towards national/global targets at the population level. Low birthweight (LBW)  98% for four hospitals) and legible > 99.9%. Weighing of stillbirths varied by hospital, ranging from 12.5-89.0%. Observed LBW rate was 15.6%; survey-reported rate 14.3% (8.9-20.9%), sensitivity 82.9% (75.1-89.4%), specificity 96.1% (93.5-98.5%); register-recorded rate 14.9%, sensitivity 90.8% (85.9-94.8%), specificity 98.5% (98-99.0%). In surveys, "don't know" responses for birthweight measured were 4.7%, and 2.9% for knowing the actual weight. 95.9% of observed babies were weighed within 1 h of birth, only 14.7% with a digital scale. Weight heaping indices were around two-fold lower using digital scales compared to analogue. Observed heaping was almost 5% higher for births during the night than day. Survey-report further increased observed birthweight heaping, especially for LBW babies. Enablers to register birthweight measurement in qualitative interviews included digital scale availability and adequate staffing. CONCLUSIONS: Hospital registers captured birthweight and LBW prevalence more accurately than women's survey report. Even in large hospitals, digital scales were not always available and stillborn babies not always weighed. Birthweight data are being captured in hospitals and investment is required to further improve data quality, researching of data flow in routine systems and use of data at every level

A Metabolomic View of Staphylococcus aureus and Its Ser/Thr Kinase and Phosphatase Deletion Mutants: Involvement in Cell Wall Biosynthesis

SummaryLittle is known about intracellular metabolite pools in pathogens such as Staphylococcus aureus. We have studied a particular metabolome by means of the presented LC-MS method. By investigating the central carbon metabolism which includes most of the energy transfer molecules like nucleotides, sugar mono- and biphosphates, and cofactors, a conclusion about phenotypes and stress answers in microorganisms is possible. Quantitative metabolite levels of S. aureus grown in complex lysogeny broth and in minimal medium were compared in the wild-type S. aureus strain 8325 and the isogenic eukaryotic-like protein serine/threonine kinase (ΔpknB) and phosphatase (Δstp) deletion mutants. Detection of several remarkable differences, e.g., in nucleotide metabolism and especially cell wall precursor metabolites, indicates a previously unreported importance of serine/threonine kinase/phosphatase on peptidoglycan and wall teichoic acid biosynthesis. These findings may lead to new insights into the regulation of staphylococcal cell wall metabolism

Domain structure of <i>S. aureus</i> PknB.

<p>The kinase region (PknB_SA-KD) is shown in orange. TM: transmembrane domain, PASTA: penicillin-binding protein and serine/threonine kinase associated domains.</p

Data collection and refinement statistics.

α<p>Values in parentheses are for highest resolution shell.</p>β<p>r.m.s., root mean square.</p