The Replicative DnaE Polymerase of Bacillus subtilis Recruits the Glycolytic Pyruvate Kinase (PykA) When Bound to Primed DNA Templates.

The glycolytic enzyme PykA has been reported to drive the metabolic control of replication through a mechanism involving PykA moonlighting functions on the essential DnaE polymerase, the DnaC helicase and regulatory determinants of PykA catalytic activity in Bacillus subtilis. The mutants of this control suffer from critical replication and cell cycle defects, showing that the metabolic control of replication plays important functions in the overall rate of replication. Using biochemical approaches, we demonstrate here that PykA interacts with DnaE for modulating its activity when the replication enzyme is bound to a primed DNA template. This interaction is mediated by the CAT domain of PykA and possibly allosterically regulated by its PEPut domain, which also operates as a potent regulator of PykA catalytic activity. Furthermore, using fluorescence microscopy we show that the CAT and PEPut domains are important for the spatial localization of origins and replication forks, independently of their function in PykA catalytic activity. Collectively, our data suggest that the metabolic control of replication depends on the recruitment of PykA by DnaE at sites of DNA synthesis. This recruitment is likely highly dynamic, as DnaE is frequently recruited to and released from replication machineries to extend the several thousand RNA primers generated from replication initiation to termination. This implies that PykA and DnaE continuously associate and dissociate at replication machineries for ensuring a highly dynamic coordination of the replication rate with metabolism.

Ferric quinate (QPLEX) inhibits the interaction of major outer membrane protein (MOMP) with the Lewis b (Leb) antigen and limits Campylobacter colonization in broilers.

Campylobacter jejuni colonizes hosts by interacting with Blood Group Antigens (BgAgs) on the surface of gastrointestinal epithelia. Genetic variations in BgAg expression affects host susceptibility to C. jejuni. Here, we show that the essential major outer membrane protein (MOMP) of C. jejuni NCTC11168 binds to the Lewis b (Leb) antigen on the gastrointestinal epithelia of host tissues and this interaction can be competitively inhibited by ferric quinate (QPLEX), a ferric chelate structurally similar to bacterial siderophores. We provide evidence that QPLEX competitively inhibits the MOMP-Leb interaction. Furthermore, we demonstrate that QPLEX can be used as a feed additive in broiler farming to significantly reduce C. jejuni colonization. Our results indicate that QPLEX can be a viable alternative to the preventative use of antibiotics in broiler farming to combat C. jejuni infections.

Pyruvate kinase, a metabolic sensor powering glycolysis, drives the metabolic control of DNA replication.

BACKGROUND: In all living organisms, DNA replication is exquisitely regulated in a wide range of growth conditions to achieve timely and accurate genome duplication prior to cell division. Failures in this regulation cause DNA damage with potentially disastrous consequences for cell viability and human health, including cancer. To cope with these threats, cells tightly control replication initiation using well-known mechanisms. They also couple DNA synthesis to nutrient richness and growth rate through a poorly understood process thought to involve central carbon metabolism. One such process may involve the cross-species conserved pyruvate kinase (PykA) which catalyzes the last reaction of glycolysis. Here we have investigated the role of PykA in regulating DNA replication in the model system Bacillus subtilis. RESULTS: On analysing mutants of the catalytic (Cat) and C-terminal (PEPut) domains of B. subtilis PykA we found replication phenotypes in conditions where PykA is dispensable for growth. These phenotypes are independent from the effect of mutations on PykA catalytic activity and are not associated with significant changes in the metabolome. PEPut operates as a nutrient-dependent inhibitor of initiation while Cat acts as a stimulator of replication fork speed. Disruption of either PEPut or Cat replication function dramatically impacted the cell cycle and replication timing even in cells fully proficient in known replication control functions. In vitro, PykA modulates activities of enzymes essential for replication initiation and elongation via functional interactions. Additional experiments showed that PEPut regulates PykA activity and that Cat and PEPut determinants important for PykA catalytic activity regulation are also important for PykA-driven replication functions. CONCLUSIONS: We infer from our findings that PykA typifies a new family of cross-species replication control regulators that drive the metabolic control of replication through a mechanism involving regulatory determinants of PykA catalytic activity. As disruption of PykA replication functions causes dramatic replication defects, we suggest that dysfunctions in this new family of universal replication regulators may pave the path to genetic instability and carcinogenesis.

Ultrasonographic hemodynamical and epidemiological factors in advancement of clinical manifestations in primary varicose veins.

BACKGROUND: Primary varicose veins (PVV) represent the most prominent clinical manifestation of chronic venous disease (CVD) and has a complex pathophysiological background. The aim of our study was to investigate the impact of sonographic hemodynamical and contemporary epidemiological factors on the clinical severity of PVV. METHODS: We analyzed the sonographic hemodynamical and clinical parameters from 159 consecutive CVD patients and 233 lower limbs with PVV of clinical stages C2, C3 and C4. Univariate and logistic regression analysis was performed between patients of C2 (N.=70 - 30.0%) and C3 - 4 stages and between subgroups C3 (N.=101 - 43.3%) and C4 (N.=62 - 26.6%). RESULTS: Reflux of common femoral vein and saphenofemoral junction was detected in 43.3% and 65.7%. High venous reflux rates were found at the great saphenous above and below knee (90.1% - 53.2%) and in Cockett perforators (80.5%). Logistic regression revealed that factors associated with the symptomatic C3; 4 stages were the duration of disease >10 years (P=0.015, insufficiency in two or more perforators (P<0.001) and history of 2 pregnancies (P=0.001). Analysis C3 vs. C4 showed that insufficiency in two or more perforators increased the likelihood of advanced C4 clinical stage by 2.2 times, (P=0.037). An additional significant factor was the presence of at least one incompetent Cockett perforator. CONCLUSIONS: Clinical severity of PVV is correlated with a plethora of complex anatomical, hemodynamical and epidemiological factors. Insufficiency in two or more perforators seems to play the most important role and this highlights the value of preoperative venous ultrasound mapping.

DNA replication initiation in Bacillus subtilis: structural and functional characterization of the essential DnaA-DnaD interaction.

The homotetrameric DnaD protein is essential in low G+C content gram positive bacteria and is involved in replication initiation at oriC and re-start of collapsed replication forks. It interacts with the ubiquitously conserved bacterial master replication initiation protein DnaA at the oriC but structural and functional details of this interaction are lacking, thus contributing to our incomplete understanding of the molecular details that underpin replication initiation in bacteria. DnaD comprises N-terminal (DDBH1) and C-terminal (DDBH2) domains, with contradicting bacterial two-hybrid and yeast two-hybrid studies suggesting that either the former or the latter interact with DnaA, respectively. Using Nuclear Magnetic Resonance (NMR) we showed that both DDBH1 and DDBH2 interact with the N-terminal domain I of DnaA and studied the DDBH2 interaction in structural detail. We revealed two families of conformations for the DDBH2-DnaA domain I complex and showed that the DnaA-interaction patch of DnaD is distinct from the DNA-interaction patch, suggesting that DnaD can bind simultaneously DNA and DnaA. Using sensitive single-molecule FRET techniques we revealed that DnaD remodels DnaA-DNA filaments consistent with stretching and/or untwisting. Furthermore, the DNA binding activity of DnaD is redundant for this filament remodelling. This in turn suggests that DnaA and DnaD are working collaboratively in the oriC to locally melt the DNA duplex during replication initiation.

The role of Visfatin in atherosclerotic peripheral arterial obstructive disease.

Visfatin is an adipokine molecule acting as an essential coenzyme in multiple cellular redox reactions. The increased serum levels of Visfatin have been correlated with metabolic syndrome and endothelial homeostasis. In this study we investigate the possible relationship of Visfatin serum levels with the severity and location of atherosclerotic peripheral arterial occlusive disease (PAOD). Study protocol included 45 consecutive PAOD and 20 Control patients with age >55years old. Definition of PAOD was based in Rutherord's classification (RC). End-stage PAOD patients (RC-V & -VI) were excluded from study. Data were collected prospectively and included age, gender, atherosclerotic risk factors and the body mass index (BMI). In PAOD patients recorded the PAOD's clinical stage and the presence of carotid stenosis >50%. PAOD patients divided in two subgroups, those with mild (RC-I & -II) and moderate disease (RC-III & -IV). In all serum samples Visfatin was measured, blindly, twice by anosoenzymatic technique. Statistical analysis was performed by non-parametric Mann-Whitney U test, Pearson's chi-square, One Way Anova and Kruskall-Wallis tests, as appropriate. The mean Visfatin value in PAOD and Control groups were 38.5±16.0 and 13.9±3.8ng/ml respectively (p<0.0005). In-PAOD subgroup of patients the visfatin values were not affected by demographics, BMI and atherosclerotic risk factors (p>0.05). Univariate analysis showed that severity of PAOD (mild vs severe), presence of carotid stenosis >50% and multilevel disease significantly affected outcomes (p=0.018, p=0.010 and p=0.006 respectively). In multivariate regression analysis severity of PAOD was the solely factor with strong correlation with high visfatin values (p=0.001). High Visfatin levels seem to be strongly correlated with the presence and severity of PAOD. Further and in depth investigation is needed to define the possible role of Visfatin in atherosclerosis and it's value as a potential prognostic biomarker of PAOD.