Purification and characterization of myo-inositol hexaphosphate-adenosine diphosphate phosphotransferase from Phaseolus aureus

myo-Inositol hexaphosphate adenosine diphosphate phosphotransferase transfers phosphate from myo-inositol hexaphosphate to adenosine diphosphate to synthesize adenosine triphosphate. This enzyme has been isolated and purified from ungerminated mungbean seeds and found to be different from guanosine diphosphate phosphotransferase. A purification of about 200-fold with 15% recovery has been obtained. The optimal pH of the reaction is 7.0 and is dependent on the presence of a divalent cation, i.e., Mg²⁺ and Mn²⁺. The K_m value for myo-inositol hexaphosphate has been found to be 0.41 × 10^?4m and V is 90.0 nmol of P_i transferred per milligram of protein per 20 min. K_m for ADP is 0.88 × 10^-4m and V is 83.3 nmol of phosphorus transferred to ADP per milligram of protein per 20 min. The ADP phosphotransferase reaction is reversible to the extent of about 50% of the forward reaction. dADP is partly effective as an acceptor but other ribonucleoside mono- and diphosphates cannot substitute for ADP. The products ATP and myo-inositol pentaphosphate have been confirmed by several criteria. It has also been shown that this enzyme transfers phosphate only from a specific phosphoryl group (C-2 position) of myo-inositol hexaphosphate for the synthesis of ATP and 1,3,4,5,6-myo-inositol pentaphosphate or pentakis (dihydrogen phosphate).     

Effect of continuous light and darkness on the testicular histology of toad (Bufo melanostictus)

Continuous darkness decreases spermatogenesis as well as Leydig cell function whereas continuous illumination suppresses spermatogenesis along with increased Leydig cell activity.     

Conformational studies on the ABH and Lewis blood group oligosaccharides

The possible conformations for the ABH and Lewis blood group oligosaccharides have been studied by an energy-minimisation procedure using empirical potential functions. It has been found that the conformation of the core structure is not altered significantly by the addition of l-fucose, galactose or N-acetyl galactosamine residues at the non-reducing end. Correlation of the preferred conformations with their known binding properties suggests that the differences between type 1 and type 2 structures become significant only when a large enough fragment of the determinant is considered. It is suggested that non-specific reagents may have small binding sites while the reagents that are specific for type 1 or type 2 structures may have larger binding sites. A two-pocket model has been proposed for antibodies and lectins which can distinguish the A1 and A2 antigens.     

Dietary Mannan-oligosaccharides potentiate the beneficial effects of Bifidobacterium bifidum in broiler chicken

This study investigated the effects of dietary Bifidobacterium bifidum (BFD) and mannan-oligosaccharide (MOS), as a synbiotic, on the production performance, gut microbiology, serum biochemistry, antioxidant profile and health indices of broiler chicken. Six dietary treatments were T1 (negative control), T2 (positive control-20 mg antibiotic BMD kg⁻¹ diet; BMD: bacitracin methylene disalicylate), T3 (0·1% MOS + 10⁶ CFU BFD per g feed), T4 (0·1% MOS + 10⁷ CFU BFD per g feed), T5 (0·2% MOS + 10⁶ CFU BFD per g feed) and T6 (0·2% MOS + 10⁷ CFU BFD per g feed). Significantly (P < 0·01) better growth performance and efficiency was observed in birds supplemented with 0·2% MOS along with 10⁶ CFU BFD per g of feed compared to BMD and control birds. Supplementation with 0·2% MOS along with either 10⁶ or 10⁷ CFU BFD per g feed reduced (P < 0·01) the gut coliform, Escherichia coli, total plate count, and Clostridium perfringens count and increased the Lactobacillus and Bifidobacterium count. Significantly (P < 0·01) higher serum and liver antioxidant enzyme pool, serum HDL cholesterol and lower serum glucose, triglyceride, total cholesterol, cardiac risk ratio, atherogenic coefficient and atherogenic index of plasma were observed in birds supplemented with 0·2% MOS along with 10⁶ CFU BFD per g of feed compared to control or BMD supplemented birds. Better production performance, gut microbial composition, serum biochemistry, antioxidant profile and health indices were depicted by broiler chicken supplemented with 0·2% MOS and 10⁶ CFU BFD per g of feed.     

Nitric oxide blocks cellular heme insertion into a broad range of heme proteins

Although the insertion of heme into proteins enables their function in bioenergetics, metabolism, and signaling, the mechanisms and regulation of this process are not fully understood. We developed a means to study cellular heme insertion into apo-protein targets over a 3-h period and then investigated how nitric oxide (NO) released from a chemical donor (NOC-18) might influence heme (protoporphyrin IX) insertion into seven targets that present a range of protein structures, heme ligation states, and functions (three NO synthases, two cytochrome P450's, catalase, and hemoglobin). NO blocked cellular heme insertion into all seven apo-protein targets. The inhibition occurred at relatively low (nM/min) fluxes of NO, was reversible, and did not involve changes in intracellular heme levels, activation of guanylate cyclase, or inhibition of mitochondrial ATP production. These aspects and the range of protein targets suggest that NO can act as a global inhibitor of heme insertion, possibly by inhibiting a common step in the process.     

Rotavirus activates a noncanonical ATM‐Chk2 branch of DNA damage response during infection to positively regulate viroplasm dynamics

Surveillance for maintaining genomic pristineness, a protective safeguard of great onco‐preventive significance, has been dedicated in eukaryotic cells to a highly conserved and synchronised signalling cascade called DNA damage response (DDR). Not surprisingly, foreign genetic elements like those of viruses are often potential targets of DDR. Viruses have evolved novel ways to subvert this genome vigilance by twisting canonical DDR to a skewed, noncanonical response through selective hijacking of some DDR components while antagonising the others. Though reported for many DNA and a few RNA viruses, potential implications of DDR have not been addressed yet in case of infection with rotavirus (RV), a double‐stranded RNA virus. In the present study, we aimed at the modulation of ataxia telangiectasia mutated (ATM)‐checkpoint kinase 2 (Chk2) branch of DDR in response to RV infection in vitro. We found activation of the transducer kinase ATM and its downstream effector Chk2 in RV‐SA11‐infected cells, the activation response being maximal at 6‐hr post infection. Moreover, ATM activation was found to be dependent on induction of the upstream sensor Mre11‐Rad50‐Nbs1 (MRN) complex. Interestingly, RV‐SA11‐mediated maximal induction of ATM‐Chk2 pathway was revealed to be neither preceded by occurrence of nuclear DNA damage nor transduced to formation of damage‐induced canonical nuclear foci. Subsequent investigations affirmed sequestration of MRN components as well as ATM‐Chk2 proteins away from nucleus into cytosolic RV replication factories (viroplasms). Chemical intervention targeting ATM and Chk2 significantly inhibited fusion and maturation of viroplasms leading to attenuated viral propagation. Cumulatively, the current study describes RV‐mediated activation of a noncanonical ATM‐Chk2 branch of DDR skewed in favour of facilitated viroplasm fusion and productive viral perpetuation.