Purification and functional characterization of lectin with phenoloxidase activity from the hemolymph of cockroach,Periplaneta americana

Lectins also identified as hemagglutinins are multivalent proteins and on account of their fine sugar‐binding specificity play an important role in immune system of invertebrates. The present study was carried out on the hemolymph lectin of cockroach, Periplaneta americana with appropriate screening and purification to understand its molecular as well as functional nature. The lectin from the hemolymph was purified using ion‐exchange chromatography. The approximate molecular weight of purified lectin was 340 kDa as determined by FPLC analysis. Rabbit erythrocytes were highly agglutinated with purified lectin from the hemolymph of P. americana. The hemagglutination activity (HA) of lectin was specifically inhibited by fucose. Glycoproteins also inhibited the HA activity of lectin. The amino acid sequences of the purified lectin revealed homology with amino acid sequences of allergen proteins from P. americana. Purified lectin showed the highest phenoloxidase activity against dopamine. The activators such as exogenous proteases and LPS from Escherichia coli and Salmonella minnesota significantly enhanced the PO activity of the purified lectin. Besides, the presence of copper and hemocyanin conserved domain in the purified lectin provided a new facet that insects belonging to the ancient clade such as cockroaches retained some traces of evolutionary resemblance in possessing lectin of ancient origin.     

Na-glutamine co-transporters B0AT1 in villus and SN2 in crypts are differentially altered in chronically inflamed rabbit intestine

Glutamine is a major nutrient utilized by the intestinal epithelium and is primarily assimilated via Na-glutamine co-transport (NGcT) on the brush border membrane (BBM) of enterocytes. Recently we reported that B⁰AT1 (SLC6A19) mediates glutamine absorption in villus while SN2 (SLC38A5) does the same in crypt cells. However, how B⁰AT1 and SN2 are affected during intestinal inflammation is unknown. In the present study it was shown that during chronic enteritis NGcT was inhibited in villus cells, however, it was stimulated in crypt cells. Our studies also demonstrated that the mechanism of inhibition of NGcT during chronic enteritis was secondary to a reduction in the number of B⁰AT1 co-transporters in the villus cell BBM without a change in the affinity of the co-transporter. In contrast, stimulation of NGcT in crypt cells was secondary to an increase in the affinity of SN2 for glutamine without an alteration in the number of co-transporters. Thus, glutamine assimilation which occurs via distinct transporters in crypt and villus cells is altered in the chronically inflamed intestine.     

A computer program for topographic analysis of biomolecular systems.

This program essentially generates a picture of a space filling molecular model. By precise simulation of the intersections between atoms, leaving out the 'hidden line', a good perspective is produced. Additional three dimensional information is provided by simulating reflection spots on the surface. This program has been used to visualise three dimensional surface features of biologically important molecules (e.g., valinomycin). With slight modification the program can be used to visualise enzyme active sites and receptor surfaces. It can also be used to create animated motion pictures of molecular dynamics.     

Control and integration of cell signaling pathways during C. Elegans vulval development

Vulval development in the Caenorhabditis elegans hermaphrodite represents a simple, genetically tractable system for studying how cell signaling events control cell fata decisions. Current models suggest that proper specification of vulval cell fates relies on the integration of multiple signaling systems, including one that involves a receptor tyrosine kinase (RTK)→Ras→mitogen activated protein kinase (MAPK) cascade and one that involves a LIN-12/Notch family receptor. In this review, we first discuss how genetic strategies are being used to identify and analyze components that control vulval cell fate decisions. We then describe the different signaling systems that have been elucidated and how they relate to one another. Finally, we highlight several recently characterized genes that encode positive regulators, negative regulators or potential targets of the RTK→Ras→MAPK cascade involved in vulval induction.     

Stability of protein and ribonucleic acid in Bacillus stearothermophilus.

The turnover of protein in a prototrophic strain of Bacillus stearothermophilus during exponential growth in a salts medium with glucose or succinate as carbon source was about 4 %/h and in a richer nutrient broth medium about 23 %/h. Protein degradation under non-growing conditions conformed to a similar pattern. The turnover of RNA (non-messenger) was about 1 %/h in salts medium and about 9 %/h in nutrient broth. The turnover of protein and RNA in the thermophile is thus moderate rather than massive. This conclusion was confirmed by measurement of the decay of a specific enzyme, isocitrate lyase, in the prototroph and of the overall protein turnover in a non-prototrophic strain of B. stearothermophilus. The half-lives of a number of enzyme systems in intact cells of the prototrophic thermophile at its optimum growth temperature showed some variation but indicated a significant rate of inactivation. Such decay of protein in vivo apparently accounts for the moderate protein turnover observed during growth.     

Fabrication,characterization and application of laccase–nylon 6,6/Fe3+ composite nanofibrous membrane for 3,3′-dimethoxybenzidine detoxification

Bioprocess and Biosystems Engineering - In this study, laccase was immobilized on nylon 6,6/Fe3+ composite (NFC) nanofibrous membrane and used for the detoxification of...     

Structural basis of pyrimidine specificity in the MS2 RNA hairpin-coat-protein complex.

We have determined the X-ray structures of six MS2 RNA hairpin-coat-protein complexes having five different substitutions at the hairpin loop base -5. This is a uracil in the wild-type hairpin and contacts the coat protein both by stacking on to a tyrosine side chain and by hydrogen bonding to an asparagine side chain. The RNA consensus sequence derived from coat protein binding studies with natural sequence variants suggested that the -5 base needs to be a pyrimidine for strong binding. The five -5 substituents used in this study were 5-bromouracil, pyrimidin-2-one, 2-thiouracil, adenine, and guanine. The structure of the 5-bromouracil complex was determined to 2.2 A resolution, which is the highest to date for any MS2 RNA-protein complex. All the complexes presented here show very similar conformations, despite variation in affinity in solution. The results suggest that the stacking of the -5 base on to the tyrosine side chain is the most important driving force for complex formation. A number of hydrogen bonds that are present in the wild-type complex are not crucial for binding, as they are missing in one or more of the complexes. The results also reveal the flexibility of this RNA-protein interface, with respect to functional group variation, and may be generally applicable to other RNA-protein complexes.