The mechanism of phosphatidylcholine‐induced interference of PAP (248‐286) aggregation

Seminal amyloids are well known for their role in enhancing HIV infection. Among all the amyloidogenic peptides identified in human semen, PAP_248‐286 was found to be the most active and was termed as semen‐derived enhancer of viral infection (SEVI). Although amyloidogenic nature of the peptide is mainly linked with enhancement of the viral infection, the most active physiological conformation of the aggregated peptide remains inconclusive. Lipids are known to modulate aggregation pathway of a variety of proteins and peptides and constitute one of the most abundant biomolecules in human semen. PAP_248‐286 significantly differs from the other known amyloidogenic peptides, including Aβ and IAPP, in terms of critical concentration, surface charge, fibril morphology, and structural transition during aggregation. Hence, in the present study, we aimed to assess the effect of a lipid, 1,2‐dioleoyl‐sn‐glycero‐3‐phosphocholine (DOPC), on PAP_248‐286 aggregation and the consequent conformational outcomes. Our initial observation suggested that the presence of the lipid considerably influenced the aggregation of PAP_248‐286. Further, ZDOCK and MD simulation studies of peptide multimerization have suggested that the hydrophobic residues at C‐terminus are crucial for PAP_248‐286 aggregation and are anticipated to be major DOPC‐interacting partners. Therefore, we further assessed the aggregation behaviour of C‐terminal (PAP_273‐286) fragment of PAP_248‐286 and observed that DOPC possesses the ability to interfere with the aggregation behaviour of both the peptides used in the current study. Mechanistically, we propose that the presence of DOPC causes considerable inhibition of the peptide aggregation by interfering with the peptide's disordered state to β‐sheet transition.     

Pheromone peptide cOB1 from native Enterococcus faecalis forms amyloid‐like structures: A new paradigm for peptide pheromones

Pheromone peptides are an important component of bacterial quorum‐sensing system. The pheromone peptide cOB1 (VAVLVLGA) of native commensal Enterococcus faecalis has also been identified as an antimicrobial peptide (AMP) and reported to kill the prototype clinical isolate strain of E. faecalis V583. In this study, the pheromone peptide cOB1 has shown to form amyloid‐like structures, a characteristic which is never reported for a pheromone peptide so far. With in silico analysis, the peptide was predicted to be highly amyloidogenic. Further, under experimental conditions, cOB1 formed aggregates displaying characteristics of amyloid structures such as bathochromic shift in Congo red absorbance, enhancement in thioflavin T fluorescence, and fibrillar morphology under transmission electron microscopy. This novel property of pheromone peptide cOB1 may have some direct effects on the binding of the pheromone to the receptor cells and subsequent conjugative transfer, making this observation more important for the therapeutics, dealing with the generation of virulent and multidrug‐resistant pathogenic strains.     

Multivalent Role of Human TFIID in Recruiting Elongation Components at the Promoter-Proximal Region for Transcriptional Control

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Alternative Lengthening of Telomeres through Two Distinct Break-Induced Replication Pathways

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Hydrolysis of soluble starch using Bacillus licheniformis alpha-amylase immobilized on superporous CELBEADS

In the present work, indigenously prepared rigid superporous (pore size of approximately 3 microm) cross-linked cellulose matrix (CELBEADS) has been used as a support for the immobilization of Bacillus licheniformis alpha-amylase (BLA). Optimum pH and temperature, and Michaelis-Menten constants were determined for both free and immobilized BLA. Immobilized BLA was observed to produce a different saccharide profile than free BLA at any value of dextrose equivalent. It was observed that pH, temperature, and initial starch concentration has a significant effect on the saccharide profile of starch hydrolysate produced using immobilized BLA in the batch mode, whereas the ratio of concentration of enzyme units to initial starch concentration has no influence on the same. Hence immobilized BLA can be used as an additional tool for production of maltodextrins with different saccharide profiles. Immobilized BLA has better thermostability than free BLA. Immobilized BLA was found to retain full activity even after eight batches of hydrolysis, each of 8h duration at 55 degrees C and 90 mg/mL initial starch concentration. A semiempirical model has been used for the prediction of saccharide composition of starch hydrolysate with respect to time.     

Babesia bovis: effects of cysteine protease inhibitors on in vitro growth

In the present study, we examined the effects of four kinds of cysteine protease inhibitors (E64, E64d, leupeptin, and ALLN) on the in vitro asexual growth of Babesia bovis. Of these, only the lipophilic inhibitors, E64d and ALLN, were found to effectively inhibit the growth of B. bovis. In further experiments, E64d, but not ALLN, significantly suppressed the parasite’s invasion of host erythrocytes, while both chemicals, especially ALLN, inhibited the parasite’s replication within the infected erythrocytes. These data suggested the presence of cysteine protease(s) derived from B. bovis, in which the protease(s) would play important roles in the erythrocyte invasion and/or replication processes of the parasite.     

Breakage-reunion domain of Streptococcus pneumoniae topoisomerase IV: crystal structure of a gram-positive quinolone target

The 2.7 A crystal structure of the 55-kDa N-terminal breakage-reunion domain of topoisomerase (topo) IV subunit A (ParC) from Streptococcus pneumoniae, the first for the quinolone targets from a gram-positive bacterium, has been solved and reveals a 'closed' dimer similar in fold to Escherichia coli DNA gyrase subunit A (GyrA), but distinct from the 'open' gate structure of Escherichia coli ParC. Unlike GyrA whose DNA binding groove is largely positively charged, the DNA binding site of ParC exhibits a distinct pattern of alternating positively and negatively charged regions coincident with the predicted positions of the grooves and phosphate backbone of DNA. Based on the ParC structure, a new induced-fit model for sequence-specific recognition of the gate (G) segment by ParC has been proposed. These features may account for the unique DNA recognition and quinolone targeting properties of pneumococcal type II topoisomerases compared to their gram-negative counterparts.     

Unravelling the emerging threats of microplastics to agroecosystems

Reviews in Environmental Science and Bio/Technology - In the past few decades, pollution from microplastics has emerged as an important issue on a global scale. These plastic particles are mainly...     

An aptasensor for rapid and sensitive detection of estrogen receptor alpha in human breast cancer

The analysis of estrogen receptor (ER) expression in breast carcinomas plays a crucial role in determining the endocrine responsiveness of tumors for systemic adjuvant therapy. Conventionally, the ER levels in breast carcinomas had been detected using the dextran-coated charcoal assay and radioimmunoassay, which are now substituted with safer and economic antibody-based assays such as immunohistochemistry (IHC) and enzyme-linked immunosorbent assay (ELISA). Despite a gold (Au) standard method, the IHC has been criticized for factors such as tissue fixation, antibody selection, and threshold staining for result interpretation that could falsify test accuracy and reproducibility. The quest for alternative methods of ER quantification in tissue samples paved the way for aptamer-based diagnostics. Previously, we have isolated a DNA aptamer against human ER alpha (ERα) using an in vitro evolution system. In this study, we developed an electrochemical sensor using the 76-nucleotide DNA ERα- aptamer for rapid, precise, and cost-effective detection of ERα expression in human breast cancer patients. The aptasensor was constructed by covalently immobilizing the thiolated ERα- aptamer onto a screen-printed Au electrode. Construction of aptasensors was confirmed through atomic force microscopy and differential pulse voltammetry measurements. A detection limit of 0.001 ng/ml was calculated for full-length ERα (66.2 kDa) in a detection time of 10 min. Analysis of the cancerous breast tissue samples using the ELISA and aptasensor methods enabled distinctive classification of samples into the categories of ER −ve, weak ER +ve, and strong ER +ve samples. The current change of this aptasensor lies within 5% after a storage of 60 days at 4°C. Further studies on a reasonably large sample size are required to realize the clinical potential of the sensor.     

Current advances and future directions in genetic enhancement of a climate resilient food legume crop,cowpea (Vigna unguiculata L. Walp.)

Plant Cell, Tissue and Organ Culture (PCTOC) - Cowpea (Vigna unguiculata (L.) Walp.) is a warm-season legume crop which is widely grown by resource-poor small and marginal farmers of Sub-Saharan...