Charged molecules modulate the volume exclusion effects exerted by crowders on FtsZ polymerization

14 p.-4 fig.-2 tab.We have studied the influence of protein crowders, either combined or individually, on the GTP-induced FtsZ cooperative assembly, crucial for the formation of the dynamic septal ring and, hence, for bacterial division. It was earlier demonstrated that high concentrations of inert polymers like Ficoll 70, used to mimic the crowded cellular interior, favor the assembly of FtsZ into bundles with slow depolymerization. We have found, by fluorescence anisotropy together with light scattering measurements, that the presence of protein crowders increases the tendency of FtsZ to polymerize at micromolar magnesium concentration, being the effect larger with ovomucoid, a negatively charged protein. Neutral polymers and a positively charged protein also diminished the critical concentration of assembly, the extent of the effect being compatible with that expected according to pure volume exclusion models. FtsZ polymerization was also observed to be strongly promoted by a negatively charged polymer, DNA, and by some unrelated polymers like PEGs at concentrations below the crowding regime. The influence of mixed crowders mimicking the heterogeneity of the intracellular environment on the tendency of FtsZ to assemble was also studied and nonadditive effects were found to prevail. Far from exactly reproducing the bacterial cytoplasm environment, this approach serves as a simplified model illustrating how its intrinsically crowded and heterogeneous nature may modulate FtsZ assembly into a functional Z-ring.This work was supported by Spanish government BIO2011-28941-C03 (GR and SZ) and BFU 2014-52070-C2-2-P (GR) (www.mineco.gob.es), European Commission HEALTH-F3-2009-223432 (GR) (http://ec.europa.eu/), and Human Frontiers Science Program RGP0050/2010-C102 (GR) (www.hfsp.org).Peer reviewe

Experiencia y reflexión crítica desde el Programa de Formación de Profesores Noveles de la US a su implantación práctica docente en el campo de la Historia del Arte, en una puesta en marcha de las nuevas metodologías docentes, herramientas de aprendizaje y criterios de evaluación en su aplicación directa en el aula para la docencia de asignaturas de Historia y Patrimonio dentro del Espacio Europeo de Educación Superior

Atendiendo a las líneas de trabajo y objetivos fundamentales que hemos advertido en los distintos programas de formación del profesorado novel universitario (con algunos ejemplos extraídos de programas de Universidades como Málaga, Jaume I de Castellón o la Universidad Autónoma de Barcelona) y después de haber participado activamente en el programa organizado por la Universidad de Sevilla para la formación del profesorado novel universitario, presentamos en esta comunicación una serie de reflexiones en torno a la figura y formación del profesor novel en asignaturas de patrimonio. Como punto de partida, el Programa de Formación de Profesores Noveles nace como detección de una serie de necesidades y carencias de formación docente entre el profesorado universitario de reciente incorporación. Ello ha dado lugar a la creación de un proyecto de investigación, formación y consolidación de una serie de equipos docentes constituidos a partir de profesores noveles de la Universidad de Sevilla y un profesor mentor de la misma UniversidadFollowing the work lines and main tasks noted in different training programmes for university novel teaching staff (i.e. programmes of the University of Málaga, University Jaume I de Castellón, University Autónoma de Barcelona) and having been directly involved in Seville University`s programme, hereby we bring a number of reflections about the figure and training of novel professors related to heritage subjects. The starting point of the Novel Professors Training Programme has been the detection of a series of necessities and lack of skills among the new university professors. This led to create an investigation project with several teams formed by novel professors guided by a mentor, senior professor of the same Universi

Development of benzodioxane-benzamides inhibitors of FtsZ as potent broad-spectrum antimicrobial agents

1 p.-1 graph. abst.Antimicrobial resistance is a serious worldwide health threat. The identification of novel potential antibiotic targets is one of the ways to slow down its worsening. FtsZ, one of the bacterial cell division machinery proteins, emerged in the last decade for its crucial role in bacterial replication and viability [1]. Benzamide compounds are the most studied and promising FtsZ inhibitors developed so far, due to their high anti-staphylococcal activity, their low cytotoxicity and the interesting results obtained in association with other antibiotic classes [2]. Along these lines, here we report our recent findings on a class of FtsZ inhibitors, containing a 2,6-difluoro-benzamide scaffold linked to a hydrophobically substituted 1,4-benzodioxane ring [3-6]. We firstly validated a robust computational model, which drove us to identify the structural features the 1,4-benzodioxane moiety and the alkoxy linker should possess, in order to perfectly fit the FtsZ binding pocket. We thus developed several interesting compounds, having submicromolar antibacterial activities and showing comparable inhibitory activities towards both Gram-positive (Staphylococcus aureus and Bacillus subtilis) [3,5] and Gram-negative (Escherichia coli) FtsZ. Nevertheless, these derivatives proved to be substrates of E. coli efflux pump AcrAB, thus affecting their potencies [4]. These surprising and novel results confirmed how a single molecule can target both species while maintaining potent antimicrobial activity. We set-up and performed different assays, to firstly validate FtsZ as the target of our class of compounds. Morphometric analysis and fluorescence microscopy let us evaluate the typical alterations of cell division and FtsZ inhibition, as well as the effects on FtsZ localization [6].Moreover, we took advantages of fluorescence anisotropy to investigate and assess the impact of our derivatives on the kinetics of disassembly of the GTP triggered FtsZ polymers. Furthermore, we used confocal microscopy, to evaluate the shape and the dimension of FtsZ polymers, when in presence or in absence of our compounds in solutions containing crowding agents mimicking the crowded environment in the cytoplasm.Peer reviewe

Isolation, Characterization and Lipid-Binding Properties of the Recalcitrant FtsA Division Protein from Escherichia coli

We have obtained milligram amounts of highly pure Escherichia coli division protein FtsA from inclusion bodies with an optimized purification method that, by overcoming the reluctance of FtsA to be purified, surmounts a bottleneck for the analysis of the molecular basis of FtsA function. Purified FtsA is folded, mostly monomeric and interacts with lipids. The apparent affinity of FtsA binding to the inner membrane is ten-fold higher than to phospholipids, suggesting that inner membrane proteins could modulate FtsA-membrane interactions. Binding of FtsA to lipids and membranes is insensitive to ionic strength, indicating that a net contribution of hydrophobic interactions is involved in the association of FtsA to lipid/membrane structures

Effect of high concentration of inert cosolutes on the refolding of an enzyme: carbonic anhydrase B in sucrose and ficoll 70

7 p.-6 fig.-1 tab.The kinetics of refolding of carbonic anhydrase II following transfer from a buffer containing 5 m guanidinium chloride to a buffer containing 0.5 m guanidinium chloride were studied by measuring the time-dependent recovery of enzymatic activity. Experiments were carried out in buffer containing concentrations of two "inert" cosolutes, sucrose and Ficoll 70, a sucrose polymer, at concentrations up to 150 g/liter. Data analysis indicates that both cosolutes significantly accelerate the rate of refolding to native or compact near-native conformations, but decrease the fraction of catalytically active enzyme recovered in the limit of long time. According to the simplest model that fits the data, both cosolutes accelerate a competing side reaction yielding inactive compact species. Acceleration of the side reaction by Ficoll is significantly greater than that of sucrose at equal w/v concentrations.This work was supported by the Intramural Program of NIDDK, National Institutes of Health.Peer reviewe

pH effect on cysteine and cystine behaviour at hanging mercury drop electrode

9 p.-4 fig.-2 tab.The pH effects on the electrochemical reactions of thiol and disulphide groups on mercury electrodes have been studied. These groups facilitate the oxidation of mercury from the electrode and its conversion into mercury thiolates. Under the appropriate experimental conditions, these thiolates form a compact film around the electrode. The formation of this film can be detected by the appearance of a spike current by cyclic voltammetry. Adsorption at the mercury surface of these groups is conditioned by the charge of the molecule, which in turn, is a consequence of the pH. Therefore, in cysteine solution, the compact film appears only when pH lies between the pKa1 and pKa2, and between the pKa2 and pKa3 in cystine solutions. At these pH values cysteine and cystine carry a zero net charge.Peer reviewe

Microenvironments created by liquid-liquid phase transition control the dynamic distribution of bacterial division FtsZ protein

13 p.-8 fig.The influence of membrane-free microcompartments resulting from crowding-induced liquid/liquid phase separation (LLPS) on the dynamic spatial organization of FtsZ, the main component of the bacterial division machinery, has been studied using several LLPS systems. The GTP-dependent assembly cycle of FtsZ is thought to be crucial for the formation of the septal ring, which is highly regulated in time and space. We found that FtsZ accumulates in one of the phases and/or at the interface, depending on the system composition and on the oligomerization state of the protein. These results were observed both in bulk LLPS and in lipid-stabilized, phase-separated aqueous microdroplets. The visualization of the droplets revealed that both the location and structural arrangement of FtsZ filaments is determined by the nature of the LLPS. Relocation upon depolymerization of the dynamic filaments suggests the protein may shift among microenvironments in response to changes in its association state. The existence of these dynamic compartments driven by phase transitions can alter the local composition and reactivity of FtsZ during its life cycle acting as a nonspecific modulating factor of cell function.This work was supported by the Spanish government through grants BIO2011-28941-C03 (G.R. and S.Z.) and BFU 2014-52070-C2-2-P (G.R.); by the European Commission through contract HEALTH-F3-2009-223432(G.R.); by Human Frontiers Science Program through grant RGP0050/2010-C102 (G.R.); and by the National Science Foundation through grant MCB-1244180 (C.D.K.).Peer reviewe

Nucleotide and receptor density modulate binding of bacterial division FtsZ protein to ZipA containing lipid-coated microbeads

9 p.-6 fig.ZipA protein from Escherichia coli is one of the essential components of the division proto-ring that provides membrane tethering to the septation FtsZ protein. A sedimentation assay was used to measure the equilibrium binding of FtsZ-GDP and FtsZ-GTP to ZipA immobilized at controlled densities on the surface of microbeads coated with a phospholipid mixture resembling the composition of E. coli membrane. We found that for both nucleotide-bound species, the amount of bound FtsZ exceeds the monolayer capacity of the ZipA immobilized beads at high concentrations of free FtsZ. In the case of FtsZ-GDP, equilibrium binding does not appear to be saturable, whereas in the case of FtsZ-GTP equilibrium binding appears to be saturable. The difference between the two modes of binding is attributed to the difference between the composition of oligomers of free FtsZ-GDP and free FtsZ-GTP formed in solution.This work was supported by the Spanish government through grants BFU2014-52070-C2-2-P and BFU2016-75471-C2-1-P (to G.R.). G.R. is member of the CIB Intramural Program ‘Macromolecular Machines for Better Life’ (MACBET). Research of A.P.M. is supported by the Intramural Research Program of the National Institute of Diabetes and Digestive and Kidney Diseases, NIH.Peer reviewe

An equilibrium model for the Mg2+-linked self-assembly of FtsZ in the presence of GTP or a GTP analogue

6 p.-4 fig.-2 tab.-1 graph. abst.The concerted formation of a narrow distribution of oligomeric FtsZ species in the presence of GTP or a GTP analogue under close to physiological conditions (neutral pH and 0.5 M K+) has been characterized recently by various biophysical methods [Monterroso, B., et al. (2012) Biochemistry51, 4541–4550]. An equilibrium model may semiquantitatively account for the results of this study; in the model, FtsZ self-associates in a noncooperative fashion to form linear fibrils, that upon increasing to a certain size exhibit an increasing tendency to form closed cyclic fibrils, as previously suggested [González, J. M., et al. (2005) Proc. Natl. Acad. Sci. U.S.A.102, 1895–1900]. The closed cyclic fibrils are formed when the natural curvature and flexibility of a linear oligomer bring the ends of a linear fiber sufficiently close to overcome the entropic barrier to loop closure. The size distribution of cyclic oligomers is thus a reflection of the tendency toward curvature of linear fibrils of FtsZ under the conditions used in these experiments.This work was supported by the Spanish Ministerio de Ciencia e Innovación through Grants BIO2008-04478-C03 and BIO2011-28941-C03-03, by the European Commission through Contract HEALTH-F3-2009-223432, by the Human Frontiers Science Program through Grant RGP0050/2010-C102, and by the Comunidad de Madrid through Grant S-BIO-0260/2006 to G.R.Peer reviewe

Combined analytical ultracentrifugation, light scattering, and fluorescence correlation spectroscopy studies on the functional associations of the bacterial division FtsZ protein

The combined application of different biophysical techniques - analytical ultracentrifugation, light scattering and fluorescence-based assays - to study the ligand-linked self-association and assembly properties of the cell division protein FtsZ from Escherichia coli is described. These reactions are thought to be important for the formation of the dynamic division ring that drives bacterial cytokinesis. In addition, the use of this orthogonal experimental approach to measure the interactions between FtsZ oligomers (GDP forms) and polymers (GTP forms) with two variants (a soluble form and a full-length protein incorporated in phospholipid bilayer nanodiscs) of the ZipA protein, which provides membrane tethering to FtsZ, is described as well. The power of a global analysis of the results obtained from complementary biophysical methods to discriminate among alternative self- and hetero-associating schemes and to propose a more robust description of the association reactions involved is emphasized. This orthogonal approach will contribute to complete our quantitative understanding of the initial events of bacterial divisionThis work was supported by the Spanish government through grants BIO2008-04478-C03 and BIO2011-28941-C03-03 to GR, BFU2010-14910 and BIO2011-28941-C03-02 to SZ; by the European Commission through contract HEALTH-F3-2009-223432, by Human Frontiers Science Program through grant RGP0050/2010-C102, and Comunidad de Madrid through grant S-BIO-0260/2006 to GR; and by the CSIC through grants 200980I186 and 201020I001 to SZ and CA, respectivelyPeer reviewe