Structural biology of tumor necrosis factor demonstrated for undergraduates instruction by computer simulation

Conceptualizing learning about proteins with a molecular viewer in high school based on the integration of two theoretical frameworks

The use of a molecular viewer to visualize proteins has become more prevalent in high schools in recent years. We relied on the foundations of two theoretical frameworks to analyze questions in two learning tasks designed for 10th- to 12th-grade biotechnology majors that make use of Jmol. The two theoretical frameworks were: (i) classification of scientific knowledge into content, procedural, and epistemic knowledge; and (ii) evaluation of the cognitive skills central to visual literacy in biochemistry. During the analysis, two sub-elements of procedural knowledge emerged from the data: (i) the visualization of molecular models, and (ii) the use of Jmol software features. Based on the theoretical frameworks and data analysis, we suggest a conceptualization of learning about proteins using a molecular viewer, where the scientific knowledge elements are integrated with the eight cognitive skills central to visual literacy in biochemistry. In addition, a model presenting a hierarchy for the knowledge elements and sub-elements is suggested. In this model, content knowledge is a basic requirement; without it, the other knowledge elements cannot be used. Moreover, the use of epistemic knowledge or Jmol software features is not possible without visualization of the molecular models, which requires content knowledge. This conceptualization is expected to facilitate the development of learning tasks, decrease the complexity of knowledge acquisition for students; it may also assist the teacher during the teaching process.

Structural and molecular analyses of functional epitopes and escape mutants in Japanese encephalitis virus envelope protein domain III

The Japanese encephalitis virus (JEV) is one of the vector borne causes of encephalitis found in southeastern Asia. This positive single-stranded RNA virus is a member of the Flaviviridae family, which notably includes dengue, tick-borne, West Nile, Zika as well as yellow fever, and transmits to humans by infected mosquitos. The main site of interactions for antibodies against this virus is the envelope protein domain III (ED3). The present report investigates the time-dependent structural and conformational changes of JEV ED3 functional epitopes and escape mutants by computer simulations. The results indicate the presence of significant structural differences between the functional epitopes and the escape mutants. Mutation-induced structural/conformational instabilities of this type can decrease the antibody neutralization activity. Among the different escape mutants studied here, Ser40Lys/Asp41Arg appear to be most unstable, while Ser40Glu/Asp41Leu exhibit the lowest structural variations. The highest level of escape mutation observed in Ser40Lys is linked to the relatively higher values of root mean square deviation/fluctuation found in the molecular dynamics simulation of this protein. Secondary-structure deviations and depletion of H bonding are other contributing factors to the protein’s increased instability. Overall, the proteins with residue 41 mutations are found to be structurally more ordered than those with residue 40 mutations. The detailed time-based structural assessment of the mutant epitopes described here may contribute to the development of novel vaccines and antiviral drugs necessary to defend against future outbreaks of JEV escape mutants.

Insight into the structures of Interleukin-18 systems

Structure-based molecular designs play a critical role in the context of next generation drug development. Besides their fundamental scientific aspects, the findings established in this approach have significant implications in the expansions of target-based therapies and vaccines. Interleukin-18 (IL-18), also known as interferon gamma (IFN-γ) inducing factor, is a pro-inflammatory cytokine. The IL-18 binds first to the IL-18α receptor and forms a lower affinity complex. Upon binding with IL-18β a hetero-trimeric complex with higher affinity is formed that initiates the signal transduction process. The present study, including structural and molecular dynamics simulations, takes a close look at the structural stabilities of IL-18 and IL-18 receptor-bound ligand structures as functions of time. The results help to identify the conformational changes of the ligand due to receptor binding, as well as the structural orders of the apo and holo IL-18 protein complexes.

Structure and Function of an Inflammatory Cytokine, Interleukin-2, Analyzed Using the Bioinformatic Approach

The inflammatory cytokine, interleukin-2 (IL-2), is an important regulator of cellular functions. This relatively less studied member of the interleukin protein family is responsible for multiple immuno-modulatory and immuno-stimulatory tasks, like T cell activation, triggering of natural killer cells, inflammation, as well as proliferation and progression of autoimmune diseases and cancers. In this communication we report the temporally variant structural aspects of the IL-2 ligand and its receptor interfaces, based on the available crystal structures. The intended goal of this effort is to generate simulated results that could potentially aid the designs of novel structure based therapeutics.

3D Modeling of Tumor Necrosis Factor Receptor and Tumor Necrosis Factor-bound Receptor Systems

The interactions between the tumor necrosis factor (TNF) and its receptor molecule are responsible for various signaling networks that are central to the functioning of human immune homeostasis. The present work is a computational study of certain structural aspects of this cell-signaling protein, specifically focusing on the molecular level analyses of the TNF receptor (TNF-R), guided by its crystallographic structure. We also examine the possible binding sites of the TNF onto TNF-R, and the associated interactions. The structural and conformational variations in the TNF-R and TNF bound TNF-R systems are examined in this context using molecular dynamics (MD) simulations. The time dependent variations of the dimeric TNF-R structures are compared with, and shown to be steadier than their isolated monomers. This dimeric stability is favored under acidic conditions. The results are used to further illustrate how 3D modeling and computer simulations can aid the structure-based approach to probing a ligand-receptor system.

Structural modeling of tumor necrosis factor: A protein of immunological importance

Tumor necrosis factor (TNF) is a multifunctional pro-inflammatory cytokine responsible for various immunoregulatory activities. Upon binding with its receptor, TNF triggers multiple complex signaling pathways such as the activations of nuclear factor kappa B and caspase cascade, which are the leading determining factors for cell survival or cell death. The present work studies certain modeling aspects of the TNF, with comparative structural analyses of the wild and mutant types of this protein. Additionally, nanoscale molecular dynamics simulations are performed to assess the structure-property relationships of proteins as functions of time.