8 research outputs found
Identification and characterization of a direct activator of a gene transfer agent
Gene transfer agents (GTAs) are thought to be ancient bacteriophages that have been co-opted into serving their host and can now transfer any gene between bacteria. Production of GTAs is controlled by several global regulators through unclear mechanisms. In Rhodobacter capsulatus, gene rcc01865 encodes a putative regulatory protein that is essential for GTA production. Here, I show that rcc01865 (hereafter gafA) encodes a transcriptional regulator that binds to the GTA promoter to initiate production of structural and DNA packaging components. Expression of gafA is in turn controlled by the pleiotropic regulator protein CtrA and the quorum-sensing regulator GtaR. GafA and CtrA work together to promote GTA maturation and eventual release through cell lysis. Identification of GafA as a direct GTA regulator allows the first integrated regulatory model to be proposed and paves the way for discovery of GTAs in other species that possess gafA homologues
Structure-Activity Relationship of the Antimicrobial Peptide Gomesin: the Role of Peptide Hydrophobicity in Its Interaction with Model Membranes
Antimicrobial peptides are part of the innate immune system of animals and plants. Their lytic activity against microorganisms generally depends on their ability to disrupt and permeabilize membranes. Here we study the structure activity relationship of the antimicrobial peptide gomesin (Gm), from the spider Acanthoscurria gomesiana, with large unilamellar vesicles (LUVs) composed of 3:7 palmitoyloleoyl phosphatidylglycerol: palmitoyloleoyl phosphatidylcholine. Several synthetic analogues of Gm were designed to alter the hydrophobicity/charge of the molecule, whereby selected amino acid residues were replaced by alanine. Isothermal titration calorimetry (ITC) was used to assess the thermodynamic parameters of peptide binding to LUVs and light scattering measurements were made to evaluated peptide-induced vesicle aggregation. the ability of the peptides to permeabilize vesicles was quantified through the leakage of an entrapped fluorescent probe. the activity of peptides could be quantified in terms of the leakage extent induced and their affinity to the membrane, which was largely dictated by the exothermic enthalpy change. the results show that analogues more hydrophobic than Gm display higher activity, whereas peptides more hydrophilic than Gm have their activity almost abolished. Vesicle aggregation, on the other hand, largely increases with peptide charge. We conclude that interaction of Gm with membranes depends on an interplay between surface electrostatic interactions, which drive anchoring to the membrane surface and vesicle aggregation, and insertion of the hydrophobic portion into the membrane core, responsible for causing membrane rupture/permeabilization.Fundação de Amparo Ă Pesquisa do Estado de SĂŁo Paulo (FAPESP)Conselho Nacional de Desenvolvimento CientĂfico e TecnolĂłgico (CNPq)INCT-FCxCoordenação de Aperfeiçoamento de Pessoal de NĂvel Superior (CAPES)Universidade Federal de SĂŁo Paulo, Dept Biofis, BR-04039032 SĂŁo Paulo, BrazilUniversidade Federal de SĂŁo Paulo, Dept Biofis, BR-04039032 SĂŁo Paulo, BrazilWeb of Scienc
riDOM, a Cell-Penetrating Peptide : Interaction with DNA and Heparan Sulfate
DNA condensation in the presence of polycationic molecules is a well-known phenomenon exploited in gene delivery. riDOM (retro-inverso dioleoylmelittin) is a cell-penetrating peptide with excellent transporter properties for DNA. It is a chimeric molecule where ri-melittin is fused to dioleoylphosphoethanolamine. The physical-chemical properties of riDOM in solution and in the presence of DNA and heparan sulfate were investigated with spectroscopic and thermodynamic methods. Dynamic light scattering shows that riDOM in solution aggregates to well-defined nanoparticles with a diameter of âŒ13 nm and a ζ-potential of 22 mV, composed of about 220-270 molecules. Binding of riDOM to DNA was studied with dynamic light scattering, ζ-potential measurements, and isothermal titration calorimetry and was compared with authentic melittin-DNA interaction. riDOM binds tightly to DNA with a microscopic binding constant of 5 Ă 10(7) M(-1) and a stoichiometry of 12 riDOM per 10 DNA base pairs. In the complex the DNA double strand is completely shielded by the more hydrophobic riDOM molecules. Authentic melittin binds to DNA with a much lower binding constant of 5 Ă 10(6) M(-1) and lower stoichiometry of 5 melittin per 10 DNA base pairs. The binding enthalpies for riDOM and melittin are small and the binding reactions are entropy-driven. Sulfated glycosaminoglycans such as heparan sulfate are also linear molecules with a negative charge. riDOM binding to heparan sulfate on cell surfaces can therefore interfere with DNA-riDOM binding. riDOM-heparan sulfate complex formation was characterized by isothermal titration calorimetry and spectroscopic methods. The binding constant of riDOM for heparan sulfate is K â 2 Ă 10(6) M(-1). Authentic melittin has a similar binding constant but riDOM shows a 3-fold higher packing density on heparan sulfate than the distinctly smaller melittin
THE ECOLOGY AND MORPHOLOGICAL VARIATION OF MARITES PHYLLODISTOMUM UMBLAE AND PHYLLODISTOMUM FOLIUM (TREMATODE: GORCODERIDAE) - PARASITES OF FISHES, THE BAIKAL LAKE BASIN
The work is aimed at studying the ecology and morphology of the two indicated species of the phyllodistoma and its influence on the micromorphology of the fishes excretory system. Investigated has been the morphological variation and distribution of the marites in the excretory system of the final hosts. The dynamics of the fishes infection with the phyllodistoma has been studied. The micromorphological variations of the fishes excretory system with the invasion by phyllodistoma have been describedAvailable from VNTIC / VNTIC - Scientific & Technical Information Centre of RussiaSIGLERURussian Federatio