Interaction with the 5D3 monoclonal antibody is regulated by intramolecular rearrangements but not by covalent dimer formation of the human ABCG2 multidrug transporter

Human ABCG2 is a plasma membrane glycoprotein working as a homodimer or homo-oligomer. The protein plays an important role in the protection/detoxification of various tissues and may also be responsible for the multidrug-resistant phenotype of cancer cells. In our previous study we found that the 5D3 monoclonal antibody shows a function-dependent reactivity to an extracellular epitope of the ABCG2 transporter. In the current experiments we have further characterized the 5D3-ABCG2 interaction. The effect of chemical cross-linking and the modulation of extracellular S-S bridges on the transporter function and 5D3 reactivity of ABCG2 were investigated in depth. We found that several protein cross-linkers greatly increased 5D3 labeling in ABCG2 expressing HEK cells; however, there was no correlation between covalent dimer formation, the inhibition of transport activity, and the increase in 5D3 binding. Dithiothreitol treatment, which reduced the extracellular S-S bridge-forming cysteines of ABCG2, had no effect on transport function but caused a significant decrease in 5D3 binding. When analyzing ABCG2 mutants carrying Cys-to-Ala changes in the extracellular loop, we found that the mutant C603A (lacking the intermolecular S-S bond) showed comparable transport activity and 5D3 reactivity to the wild-type ABCG2. However, disruption of the intramolecular S-S bridge (in C592A, C608A, or C592A/C608A mutants) in this loop abolished 5D3 binding, whereas the function of the protein was preserved. Based on these results and ab initio folding simulations, we propose a model for the large extracellular loop of the ABCG2 protein.     

Screening of Bacillus subtilis transposon mutants with altered riboflavin production

To identify novel targets for metabolic engineering of riboflavin production, we generated about 10,000 random, transposon-tagged mutants of an industrial, riboflavin-producing strain of Bacillus subtilis. Process-relevant screening conditions were established by developing a 96-deep-well plate method with raffinose as the carbon source, which mimics, to some extent, carbon limitation in fed batch cultures. Screening in raffinose and complex LB medium identified more efficiently riboflavin overproducing and underproducing mutants, respectively. As expected for a "loss of function" analysis, most identified mutants were underproducers. Insertion mutants in two genes with yet unknown function, however, were found to attain significantly improved riboflavin titers and yields. These genes and possibly further ones that are related to them are promising candidates for metabolic engineering. While causal links to riboflavin production were not obvious for most underproducers, we demonstrated for the gluconeogenic glyceraldehyde-3-phosphate dehydrogenase GapB how a novel, non-obvious metabolic engineering strategy can be derived from such underproduction mutations. Specifically, we improved riboflavin production on various substrates significantly by deregulating expression of the gluconeogenic genes gapB and pckA through knockout of their genetic repressor CcpN. This improvement was also verified under the more process-relevant conditions of a glucose-limited fed-batch culture.     

Elemental Analysis of Whole and Protein Separated Blood Serum of Patients with Systemic Lupus Erythematosus and Sjögren’s Syndrome

Data on the effects of selenium supplementation on clinical signs and metabolic profiles in women at risk for intrauterine growth restriction (IUGR) are scarce. This study was designed to assess the effects of selenium supplementation on clinical signs and metabolic status in pregnant women at risk for IUGR. This randomized double-blind placebo-controlled clinical trial was performed among 60 women at risk for IUGR according to abnormal uterine artery Doppler waveform. Participants were randomly assigned to intake either 100 μg selenium supplements as tablet (n = 30) or placebo (n = 30) for 10 weeks between 17 and 27 weeks of gestation. After 10 weeks of selenium administration, a higher percentage of women in the selenium group had pulsatility index (PI) of <1.45) (P = 0.002) than of those in the placebo group. In addition, changes in plasma levels of total antioxidant capacity (TAC) (P < 0.001), glutathione (GSH) (P = 0.008), and high-sensitivity C-reactive protein (hs-CRP) (P = 0.004) in the selenium group were significant compared with the placebo group. Additionally, selenium supplementation significantly decreased serum insulin (P = 0.02), homeostasis model of assessment-estimated insulin resistance (HOMA-IR) (P = 0.02), and homeostatic model assessment for B-cell function (HOMA-B) (P = 0.02) and significantly increased quantitative insulin sensitivity check index (QUICKI) (P = 0.04) and HDL-C levels (P = 0.02) compared with the placebo. We did not find any significant effect of selenium administration on malondialdehyde (MDA), nitric oxide (NO), fasting plasma glucose (FPG), and other lipid profiles. Overall, selenium supplementation in pregnant women at risk for IUGR resulted in improved PI, TAC, GSH, hs-CRP, and markers of insulin metabolism and HDL-C levels, but it did not affect MDA, NO, FPG, and other lipid profiles.Clinical trial registration number http://www.irct.ir: IRCT201601045623N64.     

Thermodynamic and structural characterization of the macrochelates formed in the reactions of copper(II) and zinc(II) ions with peptides of histidine

Copper(II) complexes of the peptides Ac-HisSarHis-NH₂, Ac-HisSarHisSarHis-NH₂ and Ac-HisSarHisSarHisSarHis-NH₂ have been studied by potentiometric, UV-Vis, CD and EPR spectroscopic methods. Stability constants for the corresponding zinc(II) complexes have also been reported. The formation of M(II)-2N_im, M(II)-3N_im and M(II)-4N_im bonded macrochelates was suggested in the pH range 5-7. The macrochelates were, however, not stable enough to prevent metal ion hydrolysis in slightly alkaline solutions. In the case of copper(II) complexes, the metal ion promoted deprotonation and coordination of the amide groups of histidyl residues were also suggested. The stability constants of macrochelate complexes were compared to the literature data reported for the macrochelates of the other peptides of histidine. It was found that the thermodynamic stability of macrochelate species is largely influenced by the number and location of histidyl residues in the peptide backbone. The highest stability was obtained for the HXHYH-type sequences, while the distant arrangement of histidyl residues resulted in a significant reduction of the stability constants.     

New short cationic antibacterial peptides. Synthesis,biological activity and mechanism of action

We report a theoretical and experimental study on a new series of small-sized antibacterial peptides. Synthesis and bioassays for these peptides are reported here. In addition, we evaluated different physicochemical parameters that modulate antimicrobial activity (charge, secondary structure, amphipathicity, hydrophobicity and polarity). We also performed molecular dynamic simulations to assess the interaction between these peptides and their molecular target (the membrane). Biophysical characterization of the peptides was carried out with different techniques, such as circular dichroism (CD), linear dichroism (LD), infrared spectroscopy (IR), dynamic light scattering (DLS), fluorescence spectroscopy and TEM studies using model systems (liposomes) for mammalian and bacterial membranes. The results of this study allow us to draw important conclusions on three different aspects. Theoretical and experimental results indicate that small-sized peptides have a particular mechanism of action that is different to that of large peptides. These results provide additional support for a previously proposed four-step mechanism of action. The possible pharmacophoric requirement for these small-sized peptides is discussed. Furthermore, our results indicate that a net +4 charge is the adequate for 9 amino acid long peptides to produce antibacterial activity. The information reported here is very important for designing new antibacterial peptides with these structural characteristics.     

High prevalence of CYP2C19*2 allele in Roma samples: study on Roma and Hungarian population samples with review of the literature

The purpose of our study was to characterise the CYP2C19*2 and CYP2C19*3 alleles in healthy Roma and Hungarian populations. DNA of 500 Roma and 370 Hungarian subjects were genotyped for CYP2C19*2 (G681A, rs4244285) and CYP2C19*3 (G636A, rs4986893) by PCR–RFLP assay and direct sequencing. Significant differences were found comparing the Roma and Hungarian populations in CYP2C19 681 GG (63.6 vs. 75.9 %), GA (31.8 vs. 23.0 %), AA (4.6 vs. 1.1 %), GA+AA (36.4 vs. 24.1 %) and A allele frequencies (0.205 vs. 0.125) (p < 0.004). Striking differences were found between Roma and Hungarian samples in CYP2C19*1 (79.5 vs. 87.4 %) and CYP2C19*2 (20.5 vs. 12.6 %) alleles, respectively (p < 0.001). None of the subjects was found to carry the CYP2C19*3 allele. Frequencies of the intermedier metabolizer phenotype defined by the *1/*2 genotype (0.318 vs. 0.230, p < 0.005) and poor metabolizer predicted by the *2/*2 genotype (0.046 vs. 0.011, p < 0.005) was significantly higher in Roma than in Hungarians, respectively. Genotype distribution of the Roma population was similar to those of the population of North India, however, a major difference was found in the frequency of the CYP2C19*2 allele, which is likely a result of admixture with European lineages. In conclusion, the frequencies of the CYP2C19 alleles, genotypes and corresponding extensive, intermediate and poor metabolizer phenotypes studied here in the Hungarian population are similar to those of other European Caucasian populations, but display clear differences when compared to the Roma population.     

Enhanced cardiac differentiation of mouse embryonic stem cells by use of the slow-turning,lateral vessel (STLV) bioreactor

Embryoid body (EB) formation is a common intermediate during in vitro differentiation of pluripotent stem cells into specialized cell types. We have optimized the slow-turning, lateral vessel (STLV) for large scale and homogenous EB production from mouse embryonic stem cells. The effects of inoculating different cell numbers, time of EB adherence to gelatin-coated dishes, and rotation speed for optimal EB formation and cardiac differentiation were investigated. Using 3 × 10⁵ cells/ml, 10 rpm rotary speed and plating of EBs onto gelatin-coated surfaces three days after culture, were the best parameters for optimal size and EB quality on consequent cardiac differentiation. These optimized parameters enrich cardiac differentiation in ES cells when using the STLV method.