Identification of the potential regions of Epap-1 that interacts with V3 loop of HIV-1 gp120

Early pregnancy associated protein-1 (Epap-1), a 90 kDa glycoprotein present in first trimester placental tissue, inhibits HIV-1 entry through interaction with HIV-1 gp120 at V3 and C5 regions. In the present study, we have identified the specific 32 mer region of Epap-1 that can interact with V3 loop. This was achieved by docking between Epap-1 molecular model and gp120 and studying the interaction of peptides with gp120 in vitro. Out of four peptides analyzed, two peptides (P-2 and P-3) showed significant interaction with V3 domain (N = 8; N = 7) of gp120. In the studies conducted using soluble gp120 and virus, peptide P-2 has shown conserved interaction at V3 loop regions recognized by 257D and F425 antibodies and higher anti-viral activity. Also, P-2 inhibited cell fusion mediated dye transfer between gp120 expressing HL2/3 and CD4 expressing Sup T1 cells suggesting its inhibition of viral entry, which is further confirmed by its action on HIV infection mediated by Tat activated beta gal expression in TZM-bl cells. Further optimization of P-2 peptide showed that the anti-viral activity and gp120 interaction residues lie in the N-terminal region of the peptide. These results together suggest that P-2 inhibits viral entry through specific interaction at V3 loop region.     

Inhibition of copper-induced aggregation of human γD-crystallin by a diimine molecule and investigations on their molecular interactions

Communicated by Ramaswamy H. Sarma     

Sequential interactions of silver–silica nanocomposite (Ag–SiO2NC) with cell wall,metabolism and genetic stability of Pseudomonas aeruginosa,a multiple antibiotic‐resistant bacterium

The study was carried out to understand the effect of silver–silica nanocomposite (Ag–SiO₂NC) on the cell wall integrity, metabolism and genetic stability of Pseudomonas aeruginosa, a multiple drug‐resistant bacterium. Bacterial sensitivity towards antibiotics and Ag–SiO₂NC was studied using standard disc diffusion and death rate assay, respectively. The effect of Ag–SiO₂NC on cell wall integrity was monitored using SDS assay and fatty acid profile analysis, while the effect on metabolism and genetic stability was assayed microscopically, using CTC viability staining and comet assay, respectively. Pseudomonas aeruginosa was found to be resistant to β‐lactamase, glycopeptidase, sulfonamide, quinolones, nitrofurantoin and macrolides classes of antibiotics. Complete mortality of the bacterium was achieved with 80 μg ml^?1 concentration of Ag–SiO₂NC. The cell wall integrity reduced with increasing time and reached a plateau of 70% in 110 min. Changes were also noticed in the proportion of fatty acids after the treatment. Inside the cytoplasm, a complete inhibition of electron transport system was achieved with 100 μg ml^?1 Ag–SiO₂NC, followed by DNA breakage. The study thus demonstrates that Ag–SiO₂NC invades the cytoplasm of the multiple drug‐resistant P. aeruginosa by impinging upon the cell wall integrity and kills the cells by interfering with electron transport chain and the genetic stability.

Significance and Impact of Study

Although the synthesis, structural characteristics and biofunction of silver nanoparticles are well understood, their application in antimicrobial therapy is still at its infancy as only a small number of microorganisms are tested to be sensitive to nanoparticles. A thorough knowledge of the mode of interaction of nanoparticles with bacteria at subcellular level is mandatory for any clinical application. The present study deals with the interactions of Ag–SiO2NC with the cell wall integrity, metabolism and genetic stability of Pseudomonas aeruginosa, which would contribute substantially in strengthening the therapeutic applications of silver nanoparticles.     

Effects of DNP on the cell surface properties of marine bacteria and its implication for adhesion to surfaces

Abstract

The effect of 2, 4-dinitrophenol (DNP) on the extracelluar polysaccharides (EPS), cell surface charge, and the hydrophobicity of six marine bacterial cultures was studied, and its influence on attachment of these bacteria to glass and polystyrene was evaluated. DNP treatment did not influence cell surface charge and EPS production, but had a significant effect on hydrophobicity of both hydrophilic (p = 0.05) and hydrophobic (p = 0.01) cultures. Significant reduction in the attachment of all the six cultures to glass (p = 0.02) and polystyrene (p = 0.03) was observed after DNP treatment. Moreover, hydrophobicity but not the cell surface charge or EPS production influenced bacterial cell attachment to glass and polystyrene. From this study, it was evident that DNP treatment influenced bacterial cell surface hydrophobicity, which in turn, reduced bacterial adhesion to surfaces.     

Magnetopriming circumvents the effect of salinity stress on germination in chickpea seeds

Chickpea seeds of Pusa 1053 (Mediterranean) and Pusa 256 (native) were magnetoprimed with 100 mT static magnetic field for 1 h to evaluate the effect of magnetopriming on germination of seeds under saline conditions. Enhanced rate of germination and seedling growth parameters (root and shoot length, and vigour indices) under different salinity levels indicated that magnetopriming was more effective in alleviating salinity stress at early seedling stage in Pusa 1053 as compared to Pusa 256. Dynamics of seed water absorption in magnetoprimed seeds showed increased water uptake in Pusa 1053 under non-saline as compared to saline conditions. This could have resulted in faster hydration of enzymes in primed seeds leading to higher rate of germination. Total amylase, protease and dehydrogenase activities were higher in primed seeds as compared to unprimed seeds under both non-saline and saline conditions. Production of superoxide radicals was enhanced in germinating seeds of both the genotypes under salinity irrespective of priming. Increased levels of hydrogen peroxide in germinating magnetoprimed seeds, under both the growing conditions, suggested its role in promotion of germination. Our results showed that magnetopriming of dry seeds of chickpea can be effectively used as a pre-sowing treatment for mitigating adverse effects of salinity at seed germination and early seedling growth.     

Structural and Biochemical Characterization of Compounds Inhibiting Mycobacterium tuberculosis Pantothenate Kinase

Mycobacterium tuberculosis, the bacterial causative agent of tuberculosis, currently affects millions of people. The emergence of drug-resistant strains makes development of new antibiotics targeting the bacterium a global health priority. Pantothenate kinase, a key enzyme in the universal biosynthesis of the essential cofactor CoA, was targeted in this study to find new tuberculosis drugs. The biochemical characterizations of two new classes of compounds that inhibit pantothenate kinase from M. tuberculosis are described, along with crystal structures of their enzyme-inhibitor complexes. These represent the first crystal structures of this enzyme with engineered inhibitors. Both classes of compounds bind in the active site of the enzyme, overlapping with the binding sites of the natural substrate and product, pantothenate and phosphopantothenate, respectively. One class of compounds also interferes with binding of the cofactor ATP. The complexes were crystallized in two crystal forms, one of which is in a new space group for this enzyme and diffracts to the highest resolution reported for any pantothenate kinase structure. These two crystal forms allowed, for the first time, modeling of the cofactor-binding loop in both open and closed conformations. The structures also show a binding mode of ATP different from that previously reported for the M. tuberculosis enzyme but similar to that in the pantothenate kinases of other organisms.