Rakhi Dasgupta

Small heat shock proteins (sHSPs), often known as molecular chaperones, are most prevalent in nature. Under certain stress-induced conditions, these sHSPs act as an ATP-independent variation and thus prevent the inactivation of various non-native substrate proteins and their aggregation. They also assist other ATP-dependent chaperones in the refolding of these substrates. In the case of prokaryotes and lower eukaryotes, the chaperone functions of sHSPs can bind a wide range of cellular proteins but preferentially protect translation-related proteins and metabolic enzymes. Eukaryotes usually encode a larger number of sHSPs than those of prokaryotes. The chaperone functions of mammalian sHSPs are regulated by phosphorylation in cells and also by temperature. Their sHSPs have different sub-cellular compartments and cell/tissue specificity. The substrate proteins of mammalian sHSPs or eukaryotic sHSPs accordingly reflect their multi-cellular complexity. The sHSPs of animals play roles in different physiological processes as cell differentiation, apoptosis, and longevity. In this work, the characterization, location, tissue specificity, and functional diversity of sHSPs from seven different mammalian species with special emphasis on humans have been studied. Through this extensive work, a novel and significant attempt have been made to classify them based on their omnipresence, tissue specificity, localization, secondary structure, probable mutations, and evolutionary significance.

Background: Invasion of HIV in human occurs through DC-SIGN’s interaction via the mucosal lining during sexual transmission. Bovine Lactoferrin (bLF) has been known to hinder this invasion via its interaction with DC-SIGN. Hitherto, protein assays have taken place but molecular-level studies remain unexplored. Methodology: The 3D structures of the three proteins were studied. After protein docking (bLF_DCSIGN and gp120_DC-SIGN), the complexes underwent simulation. Stability parameters and binding patterns with residues were explored. Results and Conclusion: ΔG values, net area for solvent accessibilities and conformational fluctuations in DC-SIGN affirm the binding of bLF with DC-SIGN to be more spontaneous and steadier contrary to that with gp120. Residue participation inferred more interactions to occur from bLF complex with a greater percentage of arginine (which strengthens the interaction) while electrostatic interaction between Lys45 (bLF) and Glu26 (DC-SIGN) strengthened the complex. Arg37 played an active role from DC-SIGN to form the stabilizing charged-neutral H-bond, while Lys63 from bLF formed two more such stabilizing charged-neutral H-bond with DC-SIGN. The prime binding sites in DC-SIGN; Arg37 and Gln34 occupy helices. The binding pockets in DC-SIGN may be blocked by bLF spontaneously, to hinder their interaction with gp120. No ionic-ionic interaction was observed from gp120_DCSIGN complex. 88^th residue, which was a predominant residue in the binding pocket was found to experience a conformational shift from coils to sheets after interaction of DC-SIGN with bLF. This would instigate the pharmaceutical research as non-toxic LF would be economic as a remarkable peptide inhibitor opposing HIV.

Cells can withstand the effects of temperature stress by activating small heat shock proteins IbpA and IbpB. Lon protease employing Ser679 – Lys722 catalytic dyad proteolyze IbpA and IbpB in their free forms, at physiological temperature i.e. without any temperature stress. However, the proteolytic activity of IbpA and IbpB is affected when the catalytic dyad residue of Lon protease is mutated. The mutation S679A in Lon protease brings about some changes so that the proteolytic interactions between the small heat shock proteins with that of the mutant Lon protease are lost which makes a difference in the interaction pattern of mutant Lon protease with their substrates. In the present study, we made an attempt through in-silico approach to figure out the underlying aspects of the interactions between the small heat shock proteins IbpA and IbpB with mutant Lon protease in Escherichia coli . We have tried to decipher the molecular details of the mechanism of interaction of proteolytic machinery of small heat shock proteins and mutant Lon protease with S679A mutation at physiological temperature in absence cellular temperature stress. Our study may therefore be helpful to decode the mechanistic details of the correlation with IbpA, IbpB and S679A mutant Lon protease in E. coli .

Introduction: With advances in proteomics, it is essential to investigate the molecularlevel participation of IL27 and gp130 to hinder HIV infection. Their interaction causes cell-cycle arrest in HIV+ cells by activating the receptor-associated JAK signaling and causing apoptosis of cancerous cells. Methodology: The best human wild-type WT_IL27 model was prepared after varied molecular modeling techniques. The vital tyrosine residues in WT_IL27 were identified, mutated and IL27 was re-modeled. Both wild-type and mutant IL27 were docked individually with human gp130 ectodomain complex. Best cluster sized complex was opted and the complexes (WT and MT) were MD (molecular dynamics) simulated. Protein-protein interacting residues, binding patterns, thermodynamic stability, solvent accessibility and many such parameters were evaluated to affirm the stability in the mutant complex. Statistical significances were drawn too. Result and Discussion: With statistical significances also, the mutant type (MT) IL27 was comprehended as the most stable one. Their functionality remained the same. Ionic interactions were the most dominating ones. Exceptionally several Arg residues from MT_IL27 appeared to play a major role, thereby stabilizing the simulated MT_IL27-gp130 complexes. Manifold energy estimations for the complexes, electrostatic potential and increment in %helices and %β-sheets revealed the simulated MT_IL27-gp130 complex to be more stable. In the MT_complex, residues forming 3-ten helices remained constant with major increase in α–helices. This thereby infers the complex as the steadiest and most interactive one. Conclusion: The residual exploration with the detailed structural analysis would aid in the effective drug discovery by targeting the drugs at the interacting sites with the specific binding patterns as analyzed from the study. Conformational stability and other several parameters for thermodynamic stability and accomplishment of strong interaction were also explored. Altogether, this probe provides a limelight towards the mutational alterations in WT IL27, which might allow it to act as a strong peptide inhibitor by shielding HIV entry, more potently.