Independence between GTPase active sites in the Escherichia coli cell division protein FtsZ

AbstractWe have analyzed the substrate kinetics of the GTPase activity of FtsZ and the effects of two different GTPase inhibitors, GDP and the slowly hydrolyzable GTP analogue GMPCPP. In the absence of inhibitors the GTPase activity follows simple Michaelis–Menten kinetics, and both GDP and GMPCPP inhibited the activity in a competitive manner. These results indicate that the GTPase active sites in FtsZ filaments are independent of each other, a feature relevant to elucidate the role of GTP hydrolysis in FtsZ function and cell division.Structured summary of protein interactionsFtsZ and FtsZ bind by light scattering (View interaction)

The cell division protein FtsZ from Streptococcus pneumoniae exhibits a GTPase activity delay

© 2015 by The American Society for Biochemistry and Molecular Biology, Inc.. The cell division protein FtsZ assembles in vitro by a mechanism of cooperative association dependent on GTP, monovalent cations, and Mg2+. We have analyzed the GTPase activity and assembly dynamics of Streptococcus pneumoniae FtsZ (Spn-FtsZ). SpnFtsZ assembled in an apparently cooperative process, with a higher critical concentration than values reported for other FtsZ proteins. It sedimented in the presence of GTP as a high molecular mass polymer with a well defined size and tended to form double-stranded filaments in electron microscope preparations. GTPase activity depended on K+ and Mg2+ and was inhibited by Na+. GTP hydrolysis exhibited a delay that included a lag phase followed by a GTP hydrolysis activation step, until reaction reached the GTPase rate. The lag phase was not found in polymer assembly, suggesting a transition from an initial non-GTP-hydrolyzing polymer that switches to a GTP-hydrolyzing polymer, supporting models that explain FtsZ polymer cooperativity.Spanish Government GrantsBIO2011-28941-C03 (to G. R. and C. A.) and BIO2011-28941-C01; Torres Quevedo Program Grant PTQ-11-05049 to Biomol Informatics S.L.Peer Reviewe

Screening of Trace Elements in Hair of the Female Population with Different Types of Cancers in Wielkopolska Region of Poland

Background. Cancer constitutes a major health problem worldwide. Thus, search for reliable and practical markers of the disease process remains the key issue of the diagnostic process. Objectives. The study aims at linking the trace element status of an organism, assessed by hair analysis, with the occurrence of cancer diseases. Material and Methods. Hair samples were collected from 299 patients with cancer diseases confirmed by a histopathological test and from 100 controls. Cancer patients were divided into three groups, depending on cancer type: hormone-dependent cancer, cancer of the alimentary tract, and cancer with high glycolytic activity. Mineral element analysis of hair was performed using an atomic emission spectrophotometer with inductively coupled plasma (ICP-OES) and inductively coupled plasma mass spectrometry (ICP-MS). Results. Statistically significantly lower concentrations of selenium, zinc, copper, germanium and boron, iron, and magnesium were observed in the three groups of cancer patients. Disturbance in the axis glucose-insulin and changes in concentrations of heavy metals and toxic elements were also noted. Conclusions. It seems safe to conclude that our results confirmed usefulness of hair element analysis in screening tests for the assessment of the biomarker of various cancer diseases in a female population

GENERAL LEVEL OF KNOWLEDGE ABOUT BRIEF SOLUTION FOCUSED THERAPY (BSFT) IN POLISH ADDICTION TREATMENT CENTERS

Background: The aim of this study was to estimate the level of knowledge about Brief Solution Focused Therapy (BSFT) among therapists and patients during treatment and identification of existing barriers to the introduction of the method. Subjects and methods: 64 therapists were examined in total; 37 women (57%) and 27 males (43%). The study involved also 191 patients, 160 men (83.77%) and 31 women (16.23%). All the surveys were anonymous and were collected in health centers within the province of Silesia. Results: More than 2/3 of therapists have heard of the method, but do not know the specifics of it. The most important sources of knowledge are other therapists, literature, and mass media. According to the respondents the most important barriers to alcohol addiction treatment include cultural barriers, such as embarrassment or fear of stigmatization. Younger Patients and those treated for a shorter period, state that they know the name of the current method of treatment to a lesser extent than other subgroups. About 10% of people have not heard about the BSFT method of treatment. Conclusions: The level of knowledge about the BSFT method suggests the need to promote this model among both therapists and patients. An introduction of BSFT can improve the treatment of alcohol addiction

GENERAL LEVEL OF KNOWLEDGE ABOUT BRIEF SOLUTION FOCUSED THERAPY (BSFT) IN POLISH ADDICTION TREATMENT CENTERS

Background: The aim of this study was to estimate the level of knowledge about Brief Solution Focused Therapy (BSFT) among therapists and patients during treatment and identification of existing barriers to the introduction of the method. Subjects and methods: 64 therapists were examined in total; 37 women (57%) and 27 males (43%). The study involved also 191 patients, 160 men (83.77%) and 31 women (16.23%). All the surveys were anonymous and were collected in health centers within the province of Silesia. Results: More than 2/3 of therapists have heard of the method, but do not know the specifics of it. The most important sources of knowledge are other therapists, literature, and mass media. According to the respondents the most important barriers to alcohol addiction treatment include cultural barriers, such as embarrassment or fear of stigmatization. Younger Patients and those treated for a shorter period, state that they know the name of the current method of treatment to a lesser extent than other subgroups. About 10% of people have not heard about the BSFT method of treatment. Conclusions: The level of knowledge about the BSFT method suggests the need to promote this model among both therapists and patients. An introduction of BSFT can improve the treatment of alcohol addiction

Unite to divide: Oligomerization of tubulin and actin homologs regulates initiation of bacterial cell division [version 1; referees: 3 approved]

To generate two cells from one, bacteria such as Escherichia coli use a complex of membrane-embedded proteins called the divisome that synthesize the division septum. The initial stage of cytokinesis requires a tubulin homolog, FtsZ, which forms polymers that treadmill around the cell circumference. The attachment of these polymers to the cytoplasmic membrane requires an actin homolog, FtsA, which also forms dynamic polymers that directly bind to FtsZ. Recent evidence indicates that FtsA and FtsZ regulate each other’s oligomeric state in E. coli to control the progression of cytokinesis, including the recruitment of septum synthesis proteins. In this review, we focus on recent advances in our understanding of protein-protein association between FtsZ and FtsA in the initial stages of divisome function, mainly in the well-characterized E. coli system

Role of the FtsA C terminus as a switch for polymerization and membrane association.

9 p.-4 fig.Together with ATP, the C-terminal region of the essential streptococcal FtsA protein acts as an intramolecular switch to promote its polymerization and attachment to the membrane. During septation, FtsA is known to anchor the constricting FtsZ ring and, subsequently, the divisome to the membrane. Truncation of the C terminus of the streptococcal FtsA (FtsACt) facilitates a more rapid ATP-dependent polymerization in solution than is seen with the full-length protein (FtsA). The FtsACt polymers are more organized and compact than those formed in solution by FtsA, resembling the shape of the membrane-associated FtsA polymers. We find that ATP, besides being needed for polymerization, is required for the attachment of FtsA to lipid monolayers and to vesicle membranes. We propose a model in which the binding of ATP activates a switch favoring the polymerization of FtsA and at the same time driving the amphipathic helix at its C terminus to become attached to the membrane. Conversely, when FtsA is in the cytoplasm, the C terminus is not engaged in the attachment to the membrane, and it obstructs polymerization. ATP-dependent polymerization of FtsA inside membrane vesicles causes vesicle shrinkage, suggesting that, besides providing a membrane attachment for FtsZ, the FtsA C terminus may also introduce local alterations in the membrane to facilitate septation.This work was funded by grant BIO2008-04478-C03 from Spanish Ministerio de Educación y Ciencia and by contract HEALTH-F3-2009-223431 (DIVINOCELL) from the European Commission (to both M.V. and G.R.).Peer reviewe

Dielectric properties of highly resistive GaN crystals grown by ammonothermal method at microwave frequencies

Permittivity, the dielectric loss tangent and conductivity of semi-insulating Gallium Nitride crystals have been measured as functions of frequency from 10 GHz to 50 GHz and temperature from 295 to 560 K employing quasi TE0np mode dielectric resonator technique. Crystals were grown using ammonothermal method. Two kinds of doping were used to obtain high resistivity crystals; one with deep acceptors in form of transition metal ions, and the other with shallow Mg acceptors. The sample compensated with transition metal ions exhibited semi-insulating behavior in the whole temperature range. The sample doped with Mg acceptors remained semi-insulating up to 390 K. At temperatures exceeding 390 K the conductivity term in the total dielectric loss tangent of Mg compensated sample becomes dominant and it increases exponentially with activation energy of 1.14 eV. It has been proved that ammonothermal method with appropriate doping allows growth of high quality, temperature stable semi-insulating GaN crystals

Escherichia coli ZipA organizes FtsZ polymers into dynamic ring-like protofilament structures

15 p.-6 fig.-1 tab.ZipA is an essential cell division protein in Escherichia coli. Together with FtsA, ZipA tethers dynamic polymers of FtsZ to the cytoplasmic membrane, and these polymers are required to guide synthesis of the cell division septum. This dynamic behavior of FtsZ has been reconstituted on planar lipid surfaces in vitro, visible as GTP-dependent chiral vortices several hundred nanometers in diameter, when anchored by FtsA or when fused to an artificial membrane binding domain. However, these dynamics largely vanish when ZipA is used to tether FtsZ polymers to lipids at high surface densities. This, along with some in vitro studies in solution, has led to the prevailing notion that ZipA reduces FtsZ dynamics by enhancing bundling of FtsZ filaments. Here, we show that this is not the case. When lower, more physiological levels of the soluble, cytoplasmic domain of ZipA (sZipA) were attached to lipids, FtsZ assembled into highly dynamic vortices similar to those assembled with FtsA or other membrane anchors. Notably, at either high or low surface densities, ZipA did not stimulate lateral interactions between FtsZ protofilaments. We also used E. coli mutants that are either deficient or proficient in FtsZ bundling to provide evidence that ZipA does not directly promote bundling of FtsZ filaments in vivo. Together, our results suggest that ZipA does not dampen FtsZ dynamics as previously thought, and instead may act as a passive membrane attachment for FtsZ filaments as they treadmill.IMPORTANCE: Bacterial cells use a membrane-attached ring of proteins to mark and guide formation of a division septum at midcell that forms a wall separating the two daughter cells and allows cells to divide. The key protein in this ring is FtsZ, a homolog of tubulin that forms dynamic polymers. Here, we use electron microscopy and confocal fluorescence imaging to show that one of the proteins required to attach FtsZ polymers to the membrane during E. coli cell division, ZipA, can promote dynamic swirls of FtsZ on a lipid surface in vitro. Importantly, these swirls are observed only when ZipA is present at low, physiologically relevant surface densities. Although ZipA has been thought to enhance bundling of FtsZ polymers, we find little evidence for bundling in vitro. In addition, we present several lines of in vivo evidence indicating that ZipA does not act to directly bundle FtsZ polymers.This work was supported by grant GM61074 from the National Institutes of Health to W.M. and by grant BFU2016-75471-C2-1-P from the Spanish Government to G.R.Peer reviewe