An insight into the role of the N-terminal domain of Salmonella CobB in oligomerization and Zn2+ mediated inhibition of the deacetylase activity.

Prokaryotic deacetylases are classified into nicotinamide adenine dinucleotide (NAD+)-dependent sirtuins and Zn2+-dependent deacetylases. NAD+ is a coenzyme for redox reactions, thus serving as an essential component for energy metabolism. The NAD+-dependent deacetylase domain is quite conserved and well characterized across bacterial species like CobB in Escherichia coli and Salmonella, Rv1151c in Mycobacterium, and SirtN in Bacillus subtilis. E. coli CobB is the only bacterial deacetylase with a known crystal structure (PDB ID: 1S5P), which has 91% sequence similarity with Salmonella CobB (SeCobB). Salmonella encodes two CobB isoforms, SeCobBS and SeCobBL, with a difference of 37 amino acids in its N-terminal domain (NTD). The hydrophobic nature of NTD leads to the stable oligomerization of SeCobBL. The homology modeling-based predicted structure of SeCobB showed the presence of a zinc-binding motif of unknown function. Tryptophan fluorescence quenching induced by ZnCl2 showed that Zn2+ has a weak interaction with SeCobBS but higher binding affinity toward SeCobBL, which clearly demonstrated the crucial role of NTD in Zn2+ binding. In the presence of Zn2+, both isoforms had significantly reduced thermal stability, and a greater effect was observed on SeCobBL. Dynamic light scattering (DLS) studies reflected a ninefold increase in the scattering intensity of SeCobBL upon ZnCl2 addition in contrast to an ∼onefold change in the case of SeCobBS, indicating that the Zn2+ interaction leads to the formation of large particles of SeCobBL. An in vitro lysine deacetylase assay showed that SeCobB deacetylated mammalian histones, which can be inhibited in the presence of 0.25-1.00 mM ZnCl2. Taken together, our data conclusively showed that Zn2+ strongly binds to SeCobBL through the NTD that drastically alters its stability, oligomeric status, and enzymatic activity in vitro.

Probing the interaction and aggregation of lysozyme in presence of organophosphate pesticides: a comprehensive spectroscopic, calorimetric, and in-silico investigation.

Organophosphorus pesticides (OPs) are widely used in agriculture and may contaminate food or water, leading to potential health risks. However, there are few reports on the effect of OPs on protein conformation and aggregation. Hence, in this paper, we have characterized the impact of two OPs, chlorpyrifos (CPF) and methyl parathion (Para), on the model protein HEWL using biophysical and computational methods. The steady-state and time-resolved spectroscopy, Circular dichroism (CD), molecular dynamics simulation, and isothermal titration calorimetry were employed to investigate the binding interactions between HEWL and OPs. The steady-state and time-resolved fluorescence spectroscopy confirm the presence of both static and dynamic quenching between OPs and proteins. Based on fluorescence, MD, and CD results, it was found that the OPs not only show strong binding but also destabilize the protein structure and alter the secondary and tertiary structure of the protein. The molecular docking results showed that OPs entered the binding pocket of the HEWL molecule and interacted through hydrophobic and hydrogen bond interactions. The thermodynamic studies indicated that the binding was spontaneous and OPs have shown an effect on the aggregation process of HEWL. Finally, the protein aggregation process was studied using fluorescence and SDS-PAGE studies in the presence of both the OPs and found to enhance the aggregation process in the presence of OPs. These results provide insights into the potential health risks associated with OPs and highlight the importance of understanding their interactions with biological macromolecules.Communicated by Ramaswamy H. Sarma.

Eosinophil: a central player in modulating pathological complexity in asthma.

Eosinophils are the major inflammatory cells which play a crucial role in the development of allergic and non-allergic asthma phenotypes. Eosinophilic asthma is the most heterogeneous phenotype where activated eosinophils are reported to be significantly associated with asthma severity. Activated eosinophils display an array of cell adhesion molecules that not only act as an activation marker, suitable for assessing severity, but also secrete several tissue factors, cytokines and chemokines which modulate the clinical severity. Eosinophil activations are also strictly associated with activation of other hetero cellular populations like neutrophils, macrophages, mast cells, and platelets which culminate in the onset and progression of abnormal phenotypes such as bronchoconstriction, allergic response, fibrosis instigated by tissue inflammation, epithelial injury, and oxidative stress. During the activated state, eosinophils release several potent toxic signaling molecules such as major basic proteins, eosinophil peroxidase, eosinophil cationic protein (ECP), and lipid mediators, rendering tissue damage and subsequently leading to allergic manifestation. The tissue mediators render a more complex manifestation of a severe phenotype by activating prominent signaling cross-talk. Here, in the current review with the help of search engines of PubMed, Medline, etc, we have tried to shed light and explore some of the potent determinants regulating eosinophil activation leading to asthma phenotype.