Copper(II) directs formation of toxic amorphous aggregates resulting in inhibition of hen egg white lysozyme fibrillation under alkaline salt-mediated conditions

• Published in: Journal of biomolecular structure & dynamics Vol. 33; no. 5; pp. 991 - 1007
• Main Authors: Ghosh, Sudeshna, Pandey, Nitin K., Banerjee, Priyanka, Chaudhury, Koel, Nagy, Nóra Veronika, Dasgupta, Swagata
• Format: Journal Article
• Language: English
• Published: England Taylor & Francis 04.05.2015
• Subjects: Amyloid - chemistry; Amyloid - metabolism; Amyloid - pharmacology; Animals; Cell Survival - drug effects; Chickens; Circular Dichroism; Copper - chemistry; Copper - pharmacology; Cu(II) stoichiometry; cytotoxicity; Electron Spin Resonance Spectroscopy; Female; fibrillation; hen egg white lysozyme; Hydrogen-Ion Concentration; Hydrophobic and Hydrophilic Interactions; inhibition; Mice; Microscopy, Electron, Transmission; Microscopy, Fluorescence; molten globule state; Muramidase - chemistry; Muramidase - metabolism; Muramidase - ultrastructure; NIH 3T3 Cells; Protein Aggregates; Protein Binding; Protein Conformation - drug effects; Protein Structure, Secondary - drug effects; Sodium Chloride - pharmacology; Temperature; molten globule state; inhibition; hen egg white lysozyme; cytotoxicity; Cu(II) stoichiometry; fibrillation
• ISSN: 0739-1102; 1538-0254
• DOI: 10.1080/07391102.2014.921864

Hen egg white lysozyme (HEWL) adopts a molten globule-like state at high pH (~12.75) and is found to form amyloid fibrils at alkaline pH. Here, we report that Cu(II) inhibits self-association of HEWL at pH 12.75 both at 37 and 65 °C. A significant reduction in Thioflavin T fluorescence intensity, attenuation in β-sheet content and reduction in hydrophobic exposure were observed with increasing Cu(II) stoichiometry. Electron paramagnetic resonance spectroscopy suggests a 4N type of coordination pattern around Cu(II) during fibrillation. Cu(II) is also capable of altering the cytotoxicity of the proteinaceous aggregates. Fibrillar species of diverse morphology were found in the absence of Cu(II) with the generation of amorphous aggregates in the presence of Cu(II), which are more toxic compared to the fibrils alone.