Enhanced molecular chaperone activity of the small heat-shock protein αb-crystallin following covalent immobilization onto a solid-phase support

The well-characterized small heat-shock protein, αB-crystallin, acts as a molecular chaperone by interacting with unfolding proteins to prevent their aggregation and precipitation. Structural perturbation (e.g., partial unfolding) enhances the in vitro chaperone activity of αB-crystallin. Proteins often undergo structural perturbations at the surface of a synthetic material, which may alter their biological activity. This study investigated the activity of αB-crystallin when covalently bound to a support surface; αB-crystallin was immobilized onto a range of solid material surfaces, and its characteristics and chaperone activity were assessed. Immobilization was achieved via a plasma-deposited thin polymeric interlayer containing aldehyde surface groups and reductive amination, leading to the covalent binding of αB-crystallin lysine residues to the surface aldehyde groups via Schiff-base linkages. Immobilized αB-crystallin was characterized by X-ray photoelectron spectroscopy, atomic force microscopy, and quartz crystal microgravimetry, which showed that ∼300 ng cm ^-2 (dry mass) of oligomeric αB-crystallin was bound to the surface. Immobilized αB-crystallin exhibited a significant enhancement (up to 5000-fold, when compared with the equivalent activity of αB-crystallin in solution) of its chaperone activity against various proteins undergoing both amorphous and amyloid fibril forms of aggregation. The enhanced molecular chaperone activity of immobilized αB-crystallin has potential applications in preventing protein misfolding, including against amyloid disease processes, such as dialysis-related amyloidosis, and for biodiagnostic detection of misfolded proteins.