337,870 research outputs found
Mobility of the SecA 2-helix-finger is not essential for polypeptide translocation via the SecYEG complex
No full textThe bacterial ATPase SecA and protein channel complex SecYEG form the core of an essential protein translocation machinery. The nature of the conformational changes induced by each stage of the hydrolytic cycle of ATP and how they are coupled to protein translocation are not well understood. The structure of the SecA-SecYEG complex revealed a 2-helix-finger (2HF) of SecA in an ideal position to contact the substrate protein and push it through the membrane. Surprisingly, immobilization of this finger at the edge of the protein channel had no effect on translocation, whereas its imposition inside the channel blocked transport. This analysis resolves the stoichiometry of the active complex, demonstrating that after the initiation process translocation requires only one copy each of SecA and SecYEG. The results also have important implications on the mechanism of energy transduction and the power stroke driving transport. Evidently, the 2HF is not a highly mobile transducing element of polypeptide translocation
Characterization of SecA1 and SecA2 from Gram-Positive Pathogens and Discovery of Novel SecA Inhibitors
No full textDue to the emergence and dissemination of multidrug resistance, bacterial pathogens have been causing a serious public health problem in recent years. To address the existing drug resistant problem, there is an urgent need to find new antimicrobials, especially those against drug-resistant bacteria. SecA is the central component of Sec-dependent secretion pathway, which is responsible for the secretion of many essential proteins as well as many toxins and virulence factors. Two SecA homologues are indentified in some important Gram-positive pathogens. SecA1 is involved in general secretion pathway and essential for viability, whereas SecA2 contribute to secretion of specific virulence factors. The high conservation among a wide range of bacteria and no human counterpart make SecA homologues attractive targets for exploring novel antimicrobials. We hypothesize that inhibition of these SecA homologues could reduce virulence, inhibit bacteria growth, and kill bacteria. SecA1 and SecA2 from four different species were cloned, purified, and characterized. All these SecA homologues show ATPase activities, thus screening ATPase inhibitors might help to develop new antimicrobials. In this study, three structurally different classes of SecA inhibitors were developed and optimized: 1) Rose Bengal (RB) and RB analogs derived from systematical dissection RB and Structure-Activity relationship (SAR) study; 2) pyrimidine analogs derived from virtual screening based on the ATP binding pocket of EcSecA and SAR study; and 3) bistriazole analogs derived from random screening and SAR study. Several potent SecA inhibitors show promising enzymatic inhibition against SecA homologues as well as bacteriostatic and bactericidal effects. Two major efflux pumps of S. aureus, NorA and MepA, have little negative effect on the antimicrobial activities of SecA inhibitors, suggesting that targeting SecA could by-pass efflux pumps. Moreover, these inhibitors impair the secretion of important toxins of S. aureus and B. anthracis, indicating the inhibition of in vivo SecA function could reduce virulence. Target identification assays confirm that these inhibitors could directly bind to SecA homologues, and specifically identify SecA from whole cell lysate of E. coli and S. aureus, suggesting that these inhibitors are really targeting on SecA. These studies validate that SecA is a good target for development antimicrobials.Doctor of Philosophy (PhD)Biolog
The dynamic action of SecA during the initiation of protein translocation
No full textBiotechnology and Biological Sciences Research Council (BBSRC) [a doctoral training grant Ph.D. studentship to S.W. and project grant number BB/I008675/1] and the Wellcome Trust [project grant number 084452]
Understanding Chinese Medicine Patterns of Rheumatoid Arthritis and Related Biomarkers
No full textBackground: A considerable number of Rheumatoid Arthritis (RA) patients only experience side effects from treatment, with little to no actual pain relief. The combination of disease diagnosis in biomedicine and multi-disciplinary integrative approaches such as Chinese Medicine (CM), can help to identify different functional diagnosis of RA in the context of biomarker discovery. We aimed to analyse CM patterns in RA and their biomarker profiles. Methods: Four electronic databases (web of science, CINAHL, Scopus and PubMed) were searched. The reference list of all identified reports and articles were searched for additional studies. All study designs were included and no date limits were set. Studies were considered if they were published in English and explored the possible biomarkers profiles in RA patients, classified according to the American College of Rheumatology and categorized in CM as either cold, heat/hot or deficiency patterns. Methodological quality of included studies was assessed using checklists adapted from the ©Critical Appraisal Skills Programme by two independent reviewers. A narrative synthesis was conducted, using thematic analysis. Results: A total of 10 articles were included. The studies examined 77 healthy volunteers and 1150 RA patients categorized as cold, heat/hot or deficiency pattern and related biomarkers were identified individually or concomitantly. Conclusions: CM pattern differentiation based on clinical signs and symptoms showed a diverse range of biomolecules, proteins and genes from RA patients correlated well with cold, heat/hot or deficiency phenotype-based CM patterns and could be used as diagnostic biomarkers for early detection, disease monitoring and therapeutic targets
Evaluation of the Seca Inhibitors as Novel Anti-Microbial Agents
No full textThe misuse of conventional antibiotics and natural selection of the infectious bacterial population has produced drug resistance. Thus, novel effective antibiotic compounds that treat bacterial infections resistant to available therapies are needed. SecA is an indispensable ATPase of the protein translocation machinery present in all bacteria. SecA is responsible for the secretion of many essential proteins, some toxins and virulence factors, and is essential for bacterial survival. SecA has no counterpart in mammalian cells, thus provides an ideal target for developing antimicrobial agents. SCA-13 (HO) is a pyrimidine analog derived from virtual screening; it exerts the ability to inhibit SecA translocation ATPase activity with an IC50 of 75 µM. HO showed promising bacteriostatic activities against a vacomycin resistant strain of S. aureus Mu50 and B. anthracis Sterne. No significant difference in antimicrobial activity of HO was observed among efflux pump strains of S. aureus, suggesting that compound HO is not a substrate of NorA or MepA efflux pumps. Resistant mutants of E. coli NR698 selected from HO need to be characterized to gain a better understanding of the resistance mechanisms and subsequently will allow for the identification of the drug target.tru
Vilaprisan. Progesterone receptor modulator, Treatment of uterine fibroids
No full textUterine fibroids (UF) are common gynecological affections in women of reproductive age. These tumors can be asymptomatic in the majority of cases; nonetheless, they can be responsible for a multitude of clinical presentations such as abnormal uterine bleeding, chronic pelvic pain, infertility and other obstetric complications, which may significantly impact the quality of life of patients affected. At the moment, hormonal pharmacological strategies are used in the clinical practice aiming to control women’s symptoms and improve hemoglobin level before surgery. Among these, selective progesterone receptor modulators (SPRMs) have been investigated. After the wide clinical use of ulipristal acetate, vilaprisan, a novel SPRM, is currently being deeply investigated in late phase II-III trials for the treatment of UF. The aim of this brief monograph is to review the literature on the pharmacodynamics, pharmacokinetics, clinical efficacy and safety of vilaprisan for treating UF
Reversible solid oxide fuel cells as energy conversion and storage devices
No full textA reversible solid oxide fuel cell (RSOFC) system could buffer intermittent electrical generation, e.g. wind, wave power by storing electrical energy as hydrogen and heat. RSOFC were fabricated by thermoplastic extrusion of (La₀.₈Sr₀.₂)₀.₉₅MnO[subscript(3−δ)] (LSM) ceramic support tubes, which were microstructurally stable with 55% porosity at 1350°C. A composite oxygen electrode of LSM-YSZ was applied, providing a homogeneous substrate for a 20 μm - 30 μm thick YSZ electrolyte. A dip-coated 8YSZ slurry, and a painted commercial 3YSZ ink gave sintered densities of 90% and nearly 100% at 1350°C, respectively. A porous NiO/YSZ fuel electrode was also painted on. A Ag/Cu reactive air braze was unsuccessful at forming a void-free joint between the RSOFC and a 316 stainless steel gas delivery tube, as the braze did not penetrate the oxidation layer on the steel. Two alumina-based ceramic cements failed to fully seal the cell to an alumina gas delivery tube, due to thermal expansion coefficient mismatches and porosity after curing. Therefore, the maximum open circuit voltage (OCV) obtained during RSOFC testing was 0.8 V at 440°C. LSM-YSZ symmetrical cell performance measurements with oxygen pressure showed a diffusion polarisation, which was assigned to dissociative adsorption and surface diffusion of oxygen species. A collaborative RSOFC system software model showed ohmic and activation losses dominated the RSOFC, and diffusion losses were insignificant. Pressurisation from 1 to 70 bar increased the RSOFC Nernst voltage by 11% at 900°C, and reduced the entropy of the gases, reducing heat production and increasing electrical efficiency. A 500 kg Sn/Cu phase change heat store prevented the system overheating. Over a 16 h discharge-charge RSOFC cycle in the range 5 mol.% - 95 mol.% hydrogen in steam, at 20.4 A per cell or 3250 A m⁻², the electrical energy storage efficiency was 64.4%
Autophagy-dependent toxicity of amino-functionalized nanoparticles in ovarian cancer cells
No full textThe use of nanoparticles (NPs) for diagnostic and therapeutic purposes involves the risk of side effects due to the presence of reactive groups on their surface. We studied the cellular stress response to spheroid fluorescent polystyrene nanoparticles (PS-NPs) functionalized with Amino groups in two ovarian cancer cell lines differing in the expression, among others, of relevant proteins involved in endocytosis processes (Caveolin-1) and in pro-survival/pro-death pathways (PTEN and p53). While COOH-PS-NPs were not toxic, NH2-PS-NPs showed dose- and time-dependent toxicity along with the induction of autophagy. In OVCAR3 cells, which are PTEN and P53 mutated and deficient in CAV-1, autophagy was insufficient to protect the cells from NP toxicity. Accordingly, inducers of autophagy were prevented whereas the silencing of autophagy genes exacerbated NP toxicity. In contrast, in OAW42 cells, which express wild-type PTEN, P53 and CAV-1, NH2-PS-NPs strongly limited the formation of autophagosomes, along with an increased production of the mitochondrial anion superoxide and inactivation of ATG4. Preventing the production of the mitochondrial anion superoxide rescued ATG4-mediated autophagy and saved the cells. This study outlines the relevance of the genetic background in the autophagy response to toxicity provoked by NH2-functionalized PS-NPs in cancer cells
Relugolix for the treatment of uterine fibroids
No full textUterine leiomyomas represent the most common form of benign gynecological tumors affecting 20-40% of women during their life. Several therapeutic options are available for treating these patients. The use of medical treatment for myomas has largely grown in the last years, in particular for women who would refuse, postpone or are not candidates for surgery. In the last years, the clinical investigation of gonadotropin-releasing hormone (GnRH) antagonists (GnRH-ants) has emerged. This class of drugs exerts pure competitive antagonistic activity on the GnRH receptor at the pituitary gland, producing an immediate stop in the release of gonadotropins and sex steroids. Relugolix is an orally active nonpeptide GnRH-ant, recently licensed for marketing in Japan for the treatment of symptoms related to uterine myomas. Currently, several phase III clinical trials are ongoing to evaluate this molecule in this setting in the U.S. and Europe
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