Prediction and analysis of redox-sensitive cysteines using machine learning and statistical methods

Simulation of gap junction formation reveals critical role of Cys disulfide redox state in connexin hemichannel docking

Video Abstract.

Amyloid fibril reduction through covalently modified lysine in HEWL and insulin

Proteins possess a variety of nucleophiles, which can carry out different reactions in the functioning cells. Proteins endogenously and synthetically can be modified through their nucleophilic sites. The roles of these chemical modifications have not been completely revealed. These modifications can alter the protein folding process. Protein folding directly affects the function of proteins. If an error in protein folding occurs, it may cause protein malfunction leading to several neurodegenerative disorders such as Alzheimer's and Parkinson's. In this study, Hen Egg White Lysozyme (HEWL) and bovine insulin, as model proteins for studying the amyloid formation, were covalently attached with 5(6)-thiophenolfluorescein. The amyloid formation of the covalently labeled lysozyme and insulin were compared with the native proteins. Interestingly, the results indicated that the covalent attachment of fluorescein slowed down the amyloid formation of HEWL and insulin significantly. The amyloid formation was examined using Thioflavin T (ThT) fluorescence assay, circular dichroism, FTIR, and gel electrophoresis. Tandem mass spectrometry was employed to identify the sites of covalent modifications in HEWL. It turned out that two surface lysine residues (K97 and K 116) in HEWL were modified. Computational studies, including docking and molecular simulations, revealed that 5(6)-thiophenolfluorescein makes several non-covalent interactions with HEWL residues, including Lys 97, leading to the reduction of the β-sheet in the protein. Additionally, AFM analysis confirmed the amyloid fibril reduction of lysine-modified bovine insulin and HEWL. Altogether, our results expand mechanistic insights into preventing amyloid formation by providing an approach for reducing amyloid formation by modifying specific lysine residues in the proteins.

Defining roles of specific reactive oxygen species (ROS) in cell biology and physiology

'Reactive oxygen species' (ROS) is a generic term that defines a wide variety of oxidant molecules with vastly different properties and biological functions that range from signalling to causing cell damage. Consequently, the description of oxidants needs to be chemically precise to translate research on their biological effects into therapeutic benefit in redox medicine. This Expert Recommendation article pinpoints key issues associated with identifying the physiological roles of oxidants, focusing on H₂O₂ and O₂^.-. The generic term ROS should not be used to describe specific molecular agents. We also advocate for greater precision in measurement of H₂O₂, O₂^.- and other oxidants, along with more specific identification of their signalling targets. Future work should also consider inter-organellar communication and the interactions of redox-sensitive signalling targets within organs and whole organisms, including the contribution of environmental exposures. To achieve these goals, development of tools that enable site-specific and real-time detection and quantification of individual oxidants in cells and model organisms are needed. We also stress that physiological O₂ levels should be maintained in cell culture to better mimic in vivo redox reactions associated with specific cell types. Use of precise definitions and analytical tools will help harmonize research among the many scientific disciplines working on the common goal of understanding redox biology.