Structural insights into the substrate specificity of the endonuclease activity of the influenza virus cap-snatching mechanism

The endonuclease activity within the influenza virus cap-snatching process is a proven therapeutic target. The anti-influenza drug baloxavir is highly effective, but is associated with resistance mutations that threaten its clinical efficacy. The endonuclease resides within the N-terminal domain of the PA subunit (PA_N) of the influenza RNA dependent RNA polymerase, and we report here complexes of PA_N with RNA and DNA oligonucleotides to understand its specificity and the structural basis of baloxavir resistance mutations. The RNA and DNA oligonucleotides bind within the substrate binding groove of PA_N in a similar fashion, explaining the ability of the enzyme to cleave both substrates. The individual nucleotides occupy adjacent conserved pockets that flank the two-metal active site. However, the 2′ OH of the RNA ribose moieties engage in additional interactions that appear to optimize the binding and cleavage efficiency for the natural substrate. The major baloxavir resistance mutation at position 38 is at the core of the substrate binding site, but structural studies and modeling suggest that it maintains the necessary virus fitness via compensating interactions with RNA. These studies will facilitate the development of new influenza therapeutics that spatially match the substrate and are less likely to elicit resistance mutations.     

Microsatellite marker-based genetic diversity analysis of elite lentil lines differing in grain iron and zinc concentration

Trial comprising fifty lentil genotypes was conducted at three locations in India during year 2013–2014 for estimation of grain Fe and Zn concentrations and to analyze G × E interactions by employing the additive main effect and multiplication interaction model. The study revealed significant effects for genotype, environment and genotype by environment interaction for both grain Fe and Zn concentration. In this model genotypes with the IPCA score of nearly zero and mean greater than grand mean are considered as adaptable to the studied environments. For grain Fe concentration genotypes P13143, P13135, ILL2581, P2130, LL147, L4603, PL101 and Globe mutant and for grain Zn concentration genotypes P13122, P2239, P3204 and L11-245 were found stable. The diversity analysis using 20 genomic and 54 EST-SSR markers indicated that the studied genotypes were diverse. The EST-SSRs revealed lower polymorphism as compare to genomic SSRs. Two major clusters were identified with 37 % similarity. Indigenous genotypes were grouped in cluster I and all exotic accessions were grouped in cluster II indicating the role of geographic origin in diversity. Based on multi location evaluation for grain Fe and Zn concentrations and molecular characterization crosses are proposed for development of grain Fe and Zn rich varieties (P3220 × L4649 and VL103 × P2130) and development of mapping populations (P13122 × L11-287 and LL931 × P3220) for study of genetics and mapping of QTLs/gene(s).     

Molecular assessment of proteins encoded by the mitochondrial genome of Clarias batrachus and Clarias gariepinus

The population of catfish, Clarias batrachus has substantially diminished in various countries and studies show that another related species Clarias gariepinus is replacing it. The better adaptability and survivability of C. gariepinus over C. batrachus could be attributed to the metabolic differences between these two species, which is primarily regulated by mitochondrial activities. To understand the reasons behind this phenomenon, we performed in silico analyses to decipher the differences between the proteins encoded by the mitochondrial genome of these two related species. Our analysis revealed that out of thirteen, twelve proteins encoded by the mitochondrial genome of these two species have substantial variations between them. We characterised these variations by analysing their effect on secondary structure, intrinsic disorder predisposition, and functional impact on protein and stability parameters. Our data show that most of the parameters are changing between these two closely related species. Altogether, we demonstrate the molecular insights into the mitochondrial genome-encoded proteins of these two species and predict their effect on protein function and stability that might be helping C. gariepinus to gain survivability better than the C. batrachus.