A single aromatic residue in transcriptional repressor protein KorA is critical for cooperativity with its co-regulator KorB

A central feature of broad host range IncP-1 plasmids is the set of regulatory circuits that tightly control plasmid core functions under steady-state conditions. Cooperativity between KorB and either KorA or TrbA repressor proteins is a key element of these circuits and deletion analysis has implicated the conserved C-terminal domain of KorAand TrbAin this interaction. By NMR we show that KorA and KorB interact directly and identify KorA amino acids that are affected on KorB binding. Studies on mutants showed that tyrosine 84 (or phenylalanine, in some alleles) is dispensable for repressor activity but critical for the specific interaction with KorB in both in vivo reporter gene assays and in vitro electrophoretic mobility shift and co-purification assays. This confirms that direct and specific protein–protein interactions are responsible for the cooperativity observed between KorB and its corepressors and lays the basis for determining the biological importance of this cooperativity

Bisphosphonate’s effect in hepatic rat cells: An electron microscopy study

Σκοπός: Τα διφωσφονικά αποτελούν εκλεκτικούς αναστολείς της οστικής απορρόφησης και η μακροχρόνια χρήση τους έχει συσχετισθεί με ανεπιθύμητες επιδράσεις στο γαστρεντερικό σύστημα. Σκοπός της εργασίας είναι η διερεύνηση των πιθανών επιδράσεων των διφωσφονικών στη δομή των ηπατικών κυττάρων. Υλικά και μέθοδος: Ελήφθησαν δείγματα ηπατικού ιστού από δέκα θηλυκά ποντίκια Wistar ηλικίας δώδεκα μηνών που έλαβαν Αλενδρονάτη από του στόματος για 13 εβδομάδες και από δέκα θηλυκά ποντίκια Wistar ηλικίας δώδεκα μηνών που δεν έλαβαν το φάρμακο και χρησιμοποιήθηκαν ως μάρτυρες. Τα δείγματα μελετήθηκαν με το ηλεκτρονικό μικροσκόπιο. Αποτελέσματα: Στα ηπατικά κύτταρα των ποντικιών που έλαβαν Αλενδρονάτη βρέθηκαν εκτεταμένη απώλεια γλυκογόνου, διαφόρου μεγέθους κενοτόπια, διευρυμένα κολπώδη τριχοειδή, καθώς και απουσία των μικρολαχνών σε πολλά σημεία του χώρου του Disse. Συμπέρασμα: Πρόκειται για την πρώτη μελέτη με ηλεκτρονικό μικροσκόπιο ηπατικών δειγμάτων μετά τη χορήγηση διφωσφονικών, η οποία υποδεικνύει ήπια ηπατική βλάβη. Μια πιθανή συσχέτιση μεταξύ της χρήσης της Αλενδρονάτης και της ηπατικής λειτουργίας καθίσταται εμφανής. Ωστόσο, εξαιτίας του μικρού αριθμού δειγμάτων περισσότερες μελέτες είναι απαραίτητες ώστε να διαλευκανθεί αυτή η συσχέτιση.Purpose: Bisphosphonates (BPs) are selective inhibitors of osteoclast mediated bone resorption, used for the treatment of bone disorders as well as for tumors, whereas long-term bisphosphonate use is associated with adverse gastrointestinal effects. The objective of the study is to investigate the possible effects of BPs in hepatic structure. Materials and methods: Specimens from the liver of ten female 12-month old Wistar rats were used as control group and of ten female 12-month old Wistar rats to which Alendronate (Fosamax, Merck) was administered per os for 13 weeks, were used as experimental group. Samples were observed under a Transmission Electron Microscope. Results: In the experimental group, extensive depletion of the glycogen, different sized vacuoles and enlarged sinusoids were found in hepatic cells. Furthermore, there was lack of microvilli of hepatocytes in the Disse’s space. The same findings were reported in all sections of the experimental group. Conclusion: This is the first study of liver structure after the administration of bisphosphonates, with electron microscopy. This report, indicate the presence of mild hepatic damage in liver tissues studied. Our study demonstrates a possible correlation between alendronate administration and hepatic cell function, nevertheless due to the small specimen further research is needed

Strong negative self regulation of Prokaryotic transcription factors increases the intrinsic noise of protein expression

Background Many prokaryotic transcription factors repress their own transcription. It is often asserted that such regulation enables a cell to homeostatically maintain protein abundance. We explore the role of negative self regulation of transcription in regulating the variability of protein abundance using a variety of stochastic modeling techniques. Results We undertake a novel analysis of a classic model for negative self regulation. We demonstrate that, with standard approximations, protein variance relative to its mean should be independent of repressor strength in a physiological range. Consequently, in that range, the coefficient of variation would increase with repressor strength. However, stochastic computer simulations demonstrate that there is a greater increase in noise associated with strong repressors than predicted by theory. The discrepancies between the mathematical analysis and computer simulations arise because with strong repressors the approximation that leads to Michaelis-Menten-like hyperbolic repression terms ceases to be valid. Because we observe that strong negative feedback increases variability and so is unlikely to be a mechanism for noise control, we suggest instead that negative feedback is evolutionarily favoured because it allows the cell to minimize mRNA usage. To test this, we used in silico evolution to demonstrate that while negative feedback can achieve only a modest improvement in protein noise reduction compared with the unregulated system, it can achieve good improvement in protein response times and very substantial improvement in reducing mRNA levels. Conclusions Strong negative self regulation of transcription may not always be a mechanism for homeostatic control of protein abundance, but instead might be evolutionarily favoured as a mechanism to limit the use of mRNA. The use of hyperbolic terms derived from quasi-steady-state approximation should also be avoided in the analysis of stochastic models with strong repressors

Why bother with a COST Action? The benefits of networking in science

A COST Action is a consortium of -mainly- European scientists (but open to international cooperation) working on a common research area, with the same subject; COST provides funding to the Actions for networking and dissemination activities, thus the participating scientists must have secured research funding from other national or European sources. COST funding is in the scale of approximately 100 kEuros per year and in this vein, it is often criticized both in that it does not fund research and the core science and in that its funding is 'limited'. However, COST with its instruments is an integral pillar of the European Research Area, and it is through its mission that a variety of aspects of the research environment, fundamental to the success of the research, are catered for; these include scientific networking, collaboration/exchange/training and dissemination activities. Through fast procedures, proposals are evaluated and approved for funding in less than one year from submission date and Actions become operational immediately, managed on flexible management. In this way, COST contributes to reducing the fragmentation in European research investments, while opening the European Research Area to cooperation worldwide. COST Actions have an excellent record of building the critical mass for follow up activities in the EU FP or other similarly competitive programmes.© 2010 Kostelidou and Babiloni; licensee BioMed Central Ltd

The hierarchy of KorB binding at its 12 binding sits on the broad-host-range plasmid RK2 and modulation of this binding by IncD1 protein

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Single nucleotide polymorphisms of Toll-like receptors and susceptibility to infectious diseases

Toll-like receptors (TLRs) are the best-studied family of pattern-recognition receptors (PRRs), whose task is to rapidly recognize evolutionarily conserved structures on the invading microorganisms. Through binding to these patterns, TLRs trigger a number of proinflammatory and anti-microbial responses, playing a key role in the first line of defence against the pathogens also promoting adaptive immunity responses. Growing amounts of data suggest that single nucleotide polymorphisms (SNPs) on the various human TLR proteins are associated with altered susceptibility to infection. This review summarizes the role of TLRs in innate immunity, their ligands and signalling and focuses on the TLR SNPs which have been linked to infectious disease susceptibility. © 2015 British Society for Immunology